Fibers doi: 10.3390/fib14070088

Authors: Ahid Zuhair Hamoodi Zaid Ali Kadhim Alzaidi Mustafa Shareef Zewair Hawraa S. Malik

An experimental study was conducted to investigate the flexural behavior of continuous beams strengthened with precast concrete plates. Ten rectangular concrete beams with a cross-section of 210 × 150 mm and a total length of 2400 mm were tested under four-point loads. One specimen, without any strengthening, acted as the control, while the remaining nine were strengthened at both the positive and negative moment zones. The variables in this study were: strengthening plate thickness, length, type of bonding (epoxy or mechanical connector), bonding method (surface bonding or 10 mm grooving), type of concrete used (UHPC, SFRC, or SIFCON), and finally, the steel fiber ratio. The failure mode, cracking modes, ultimate load, load–deflection curve, stiffness and ductility were analyzed. The results showed the effectiveness of the strengthening methods, as they improved the flexural strength of the beams by 15.7% to 53%, as well as their stiffness by 15% to 173.8%, and reduced crack propagation. Also, decreasing the thickness and length of plates reduced the flexural strength by 7.28% and 23.5%, respectively. When the bonding methods were compared, the beam with mechanical bonding showed 5.7% more flexural strength than the one using epoxy. However, it was noted that all cracks in the strengthening plates were located at the bolt positions. Additionally, the use of SIFCON plates enhanced flexural strength more than UHPC and SFRC plates. However, for the SFRC plate, increasing the steel fiber content from 1.5% to 2% improved the strength by 1.2%, but this high percentage also caused cracking in the SFRC plate due to the inhomogeneity of the concrete mixture. As for the initial stiffness, the sample in which epoxy was used showed the highest value, with an increase of 173.8%, due to the uniform bonding at the connection surface. Finally, it was observed that the reference beam had the highest ductility due to the high ultimate displacement resulting from the numerous cracks that occurred in the beam, which were reduced in the strengthened beams.

Fibers doi: 10.3390/fib14070087

Authors: Miquel Ángel Chamorro Jaume Font Irieix Costa Jordi Soler Joan Llorens

The degradation of the natural fibers in the hydraulic binder alkaline matrix is widely known. This study investigates the effect of two fiber treatments, namely immersion in sodium hydroxide (NaOH) solution and hornification, in two types of alkaline environmental ordinary Portland cement (OPC) and a mixture of OPC and natural hydraulic lime (NHL). After curing for 28 days, the specimens were subjected to 25 and 50 dry–wet aging cycles to evaluate their degradation behavior. Subsequently, the specimens underwent flexural and compressive strength tests. This study reveals that the specimens with the mixed binder of ordinary Portland cement (OPC) and natural hydraulic lime (NHL), after 50 aging cycles, reached toughness values in the descending branch compared to the total toughness obtained in the flexural–displacement diagram, of 17% and 27% for the treatment with NaOH and hornification fiber, compared to 3% and 10% obtained for the matrix with an OPC binder. Therefore, the inclusion of NHL as a matrix binder provided better softening behavior than those with only the OPC binder, providing better protection of the fibers against environmental alkalinity due to matrix alkalinity. In addition, the hornification treatment better preserved the fibers throughout the aging process.

Fibers doi: 10.3390/fib14070086

Authors: Khakam Ma’ruf Rizal Justian Setiawan Taufik Akbar Rheina Khaisa Rhehani Putri Zaky Ahmad Aditya Afan Sutopo Muhamad Yogi Yu-Tzu Chen

Water hyacinth (Eichhornia crassipes) is an invasive aquatic plant with high lignocellulosic content, offering potential as a natural fiber resource for craft-based industries. However, its extremely high initial moisture content (≈95%) presents a major challenge in fiber processing, particularly for small-scale industries that rely on traditional sun-drying methods. These methods are highly dependent on weather conditions, prone to contamination, and produce inconsistent fiber quality. This study adopts a research and development (R&D) approach to design and evaluate an innovative dryer machine specifically for water hyacinth fiber processing. The proposed system utilizes LPG-based heating and controlled airflow to achieve stable drying conditions. Experimental results show that the dryer machine can process 10 kg of wet water hyacinth within 280 min, significantly shorter than the approximately four days required for manual drying. The system reduces the moisture content to below 10%, resulting in improved fiber cleanliness, uniformity, and usability. Although the dried mass produced by the machine is slightly lower compared to manual drying, this is attributed to more effective moisture removal, leading to lower residual water content in the final product. Productivity analysis indicates improved operational consistency and higher processing capacity over extended periods (30–180 days), particularly under varying weather conditions. These findings demonstrate that controlled drying technology provides a reliable and efficient solution for lignocellulosic fiber processing in small-scale industries, contributing to improved material utilization and sustainable biomass management.

Fibers doi: 10.3390/fib14070085

Authors: Rinat Iskakov Gulbarshin Shambilova Zhanar Kadasheva Danagul Kalimanova Meirbek Naukenov Alexander Korshunov Igor Makarov Markel Vinogradov Georgy Makarov

In this study, a new approach to stabilizing polypropylene (PP) melts using the bio-based antioxidant propyl gallate (PG) is considered. Since PG is extensively used in the food and cosmetics fields and its low doses do not cause reactions in humans, producing PP melts with PG is an interesting approach. Furthermore, PG is already actively used in the processing of natural polymers, for example, in the NMMO process. It is shown that introducing up to 0.2 wt.% PG into the system is sufficient to significantly reduce the decrease in melt viscosity during repeated PP processing. After five processing cycles, the viscosity of systems with PG decreases by less than an order of magnitude, while for melts without the antioxidant the viscosity drops by almost three orders of magnitude to 10 Pa s. For melts with antioxidant additives, the crossover point position in the frequency dependences remains virtually unchanged, indicating the preservation of the system’s elastic properties. Macrofibers were spun from the resulting melts, which can then be used for concrete reinforcement. For the spun fibers with PG, the strength decreased to 68.1 MPa after five passes, whereas for the PP fibers, the values did not exceed 31 MPa. The structure and properties of the fibers were studied using X-ray diffraction and IR spectroscopy, and contact angles were determined.

Fibers doi: 10.3390/fib14070084

Authors: Muneeb Tahir Tri Vu Abdel-Fattah M. Seyam

This study reports the filament-making stage of a sequential single-screw process-development pathway for compatibilizer- and plasticizer-free soy hull fiber (SHF)/PLA biocomposites used in fused deposition modeling. Thirty-three filament-making trials were interpreted through an event-linked process chain, and 14 trials were evaluated using phase-resolved in-line diameter records and capability-style Cp/Cpk metrics. Filament-making converged on a single-mixing-zone screw, a 3.85 mm orifice/5.75 mm land die, 10 rev/min, and a 160/170/180/195 °C barrel profile for 10–30 wt.% SHF, whereas neat PLA required 180/185/200/205 °C. The strongest sustained benchmark was a 10SHF filament produced under converged settings, with a mean diameter of 1.7411 mm, a standard deviation of 0.0236 mm, 95.45% of readings within 1.70–1.80 mm, and only 0.013% above 1.89 mm. Feed replenishment, depletion, irregular pellets, recycled material, and fines-rich feed shifted the same nominal configuration among controlled and unstable states. The highest reliably spool-fed formulation was 30 wt.% SHF. The 35SHF filament remained nozzle-depositable from loose coils but fractured repeatedly during take-up and direct spool unwinding in 3D printing. Operational validation of all four converged filament formulations comprised 720 printed mechanical-test specimens over approximately 936 h. The reported conditions define platform-specific operating windows, but the process insights hold global relevance for pellet-based extrusion systems.

Fibers doi: 10.3390/fib14070083

Authors: Jochen Straetmans Mario Smet

Carbon fibers, whose origins are closely intertwined with precursor chemistry and processing conditions, have become indispensable structural lightweight materials due to their exceptional combination of low density, high tensile strength, and high stiffness. This review aims to provide a combined overview of the mechanical properties of carbon fibers by tracing their development from the historically dominant polyacrylonitrile (PAN) and mesophase pitch systems to emerging polyethylene (PE)-based alternatives. Based on decades of fundamental and applied research, this review outlines how precursor molecular structure, stabilization pathways, and carbonization conditions direct microstructural growth and thereby mechanical performance. Established structure/property relationships in PAN and mesophase pitch fibers are discussed alongside recent insights into the sulfonation, crosslinking, and carbonization behavior of PE-based precursor systems. Additionally, this review presents current knowledge on production costs, market dynamics, and the environmental impact of carbon fiber manufacturing, highlighting how energy-intensive processing remains a key barrier to broader industrial adoption. Combined, the findings presented in this review provide an integrated basis describing how precursor selection, processing strategy, and resulting morphology shape mechanical behavior and clarify the position of PE-based carbon fibers within the broader landscape of cost, performance, and sustainability.

Fibers doi: 10.3390/fib14070082

Authors: Wang Xu Yunchu Yang Abdel-Fattah Seyam

This study examines how yarn microstructure influences isothermal water-vapor transport and the associated evaporative heat loss under ISO 11092 skin-model conditions. Sweating guarded hotplate experiments were performed on PET yarn-array specimens to measure evaporative heat flux and moisture resistance. A fiber-level two-dimensional finite element model was then developed to reproduce the same boundary conditions and simulate transport through a PET fiber/air matrix. Using a full-factorial design, denier per filament, the number of filaments, and packing factor were varied independently, with multiple random filament arrangements used for each parameter combination to account for microstructural variability. The model reproduced the main experimental trends and gave predictions consistent with measured heat flux and moisture resistance for representative yarn configurations. Over the investigated design space, packing factor had the strongest influence: higher packing reduced heat and moisture flux and increased moisture resistance. Denier per filament and the number of filaments showed smaller but systematic effects, mainly through changes in pore connectivity and tortuosity. Statistical analysis indicated that main effects accounted for most response variation, while interaction effects were limited within the studied ranges. Flow-field results further showed a shift from internal flow penetration at low packing to bypass-dominated transport at high packing. These findings provide a validated framework for linking yarn-level structural parameters with heat–moisture transport performance in fibrous assemblies.

Fibers doi: 10.3390/fib14070081

Authors: Long Ling Aijun Chen Yifan Zhou Yanping Liu

Expansive soil is highly susceptible to water-softening and desiccation cracking under alternating wet–dry conditions, often resulting in severe geotechnical and geological hazards. To mitigate these undesirable engineering properties, a composite improvement approach utilizing biochar and sisal fiber was employed. The shear strength and cracking characteristics of the improved expansive soil were systematically investigated through direct shear tests and desiccation cracking tests on specimens prepared with varying biochar contents, sisal fiber contents, and fiber lengths. Scanning electron microscopy (SEM) was further conducted to elucidate the underlying microstructural mechanisms. The results indicated that the individual addition of biochar or sisal fiber enhanced the shear strength of the expansive soil. Increasing the biochar content from 4% to 10% yielded an 8–19% strength gain, whereas raising the sisal fiber content from 1.5‰ to 6‰ led to a more substantial 36–110% improvement. Conversely, extending the fiber length from 10 mm to 30 mm diminished the shear strength by 11–21%. Higher biochar contents progressively increased the internal friction angle (from 14.84° to 18.52°) but were accompanied by a decline in cohesion (from 9.0 kPa to 4.0 kPa). In contrast, increasing the sisal fiber content markedly enhanced cohesion (from 4.7 kPa to 50.3 kPa) while marginally reducing the internal friction angle (from 15.2° to 12.8°). In terms of crack suppression, a 10% biochar content achieved an 86.8% reduction in crack ratio, while 6‰ sisal fiber yielded a 72.4% reduction. Range analysis revealed that crack length and crack ratio were most sensitive to biochar content, whereas crack width was predominantly governed by fiber content. Notably, surface cracking was completely eliminated in the composite specimen prepared with 10% biochar, 4.5‰ sisal fiber, and a fiber length of 20 mm. Microstructural analysis revealed that biochar particles featured rough surfaces and abundant internal pores, while the sisal fibers formed a randomly interwoven network within the soil matrix. The synergistic interplay between the rigid biochar skeleton and the flexible fiber network contributed to the substantial enhancement in both mechanical strength and crack resistance.

Fibers doi: 10.3390/fib14070080

Authors: Javier Pisonero Enrique González-González Manuel Rodríguez-Martín Roberto García-Martín

Filament–wound carbon fiber composites are widely used in lightweight structural applications, where their mechanical performance is strongly affected by manufacturing-induced heterogeneities. In this study, the tensile behavior of carbon fiber composite specimens produced by filament winding was investigated using Digital Image Correlation (DIC) to obtain full-field strain measurements. Uniaxial tensile tests were performed while monitoring the spatial distribution of strain over the specimen surface. Beyond conventional global stress–strain characterization, DIC enabled the identification of significant strain heterogeneity both within individual specimens and among different specimens manufactured under the same nominal conditions. Localized strain concentrations were observed to develop in specific regions, revealing non-uniform deformation patterns that were not captured by global measurements alone. The results demonstrate that, despite similar global mechanical responses, substantial variability exists at the local scale. This intra and inter-specimen heterogeneity highlights the influence of filament winding architecture and local variability on tensile performance. The study underscores the limitations of relying solely on global measurements and emphasizes the capability of DIC to provide deeper insight into strain distribution and damage initiation mechanisms. These findings support the use of full-field optical techniques as a powerful tool for the mechanical characterization and quality assessment of filament–wound composite structures.

Fibers doi: 10.3390/fib14070079

Authors: Peter El Hage Roland El Hage César Segovia Jingjing Liao Didilia Ileana Mendoza-Castillo Nicolas Brosse Henri Vahabi

In response to the increasing needs for environmentally friendly products, lignocellulosic natural fibers have been of interest as potential replacements for synthetic reinforcement materials in textiles, composites, and related applications. Among these resources, bast fibers derived from plant stems (flax, hemp, nettle, jute, hop), which contain a high cellulose content, have good mechanical properties, low density, and are renewable, are highly promising. Steam explosion has emerged as a green fiber extraction, defibrillation, and surface modification pretreatment technology. Despite the growing number of studies on steam-exploded natural fibers, a comprehensive understanding of the relationships between processing conditions, fiber modifications, mechanisms, and end-use performance remains limited. This review investigates the structural, chemical, and morphological influences of steam explosion on bast fibers. Specifically, it focuses on the mechanism of steam explosion including the solubilization of hemicellulose, partial lignin redistribution or removal, fiber individualization, and cellulose enrichment. The literature indicates that steam explosion can improve fiber separation, fineness, surface morphology, and interfacial adhesion of the composite materials and reduce the use of hazardous chemicals compared with conventional extraction methods. Nonetheless, conflicting results have also been documented, where the same steam explosion conditions can yield distinct fiber characteristics according to biomass type, composition of biomass, moisture concentration, and the amount of processing involved. Excessive treatment severity may lead to fiber shortening, cellulose degradation, and deterioration of fiber quality, particularly for textile applications requiring long fibers. This review highlights current knowledge gaps regarding the optimization of processing conditions, the understanding of steam explosion mechanisms, and the scale-up of the technology for industrial applications.

Fibers doi: 10.3390/fib14070078

Authors: Maciej Milewski

This study examines the effect of small ply angle deviations on the structural response of carbon fiber-reinforced polymer laminates representative of structures used in unmanned aerial vehicles (UAVs). A combined experimental and numerical approach was applied, including cantilever bending tests and experimental modal analysis, supported by finite element simulations. Laminates with nominal ply orientations of 0°, 5°, and 10° were manufactured using a manual hand lay-up process to reflect typical production variability. The results show that the numerical model accurately captures the observed trends in both bending deformation and natural frequencies, with discrepancies up to 12.5%. A consistent tendency to slightly overestimate stiffness was observed, leading to lower predicted deflections and higher natural frequencies compared to experimental data. The findings confirm that finite element modeling can reliably detect and predict the structural effects of small fiber misalignment, supporting its use in the assessment and design of lightweight composite structures used in UAV applications.

Fibers doi: 10.3390/fib14070077

Authors: Konstantinos E. Bantralexis Eleni S. Boura Ioannis N. Markou Evangelos D. Evangelou

Improvement of the engineering properties of soils by reinforcing them with fibers, at an appropriate percentage of the weight of dry soil, is frequently selected to ensure the safe construction and operation of many structures. However, the published information regarding the investigation of the dynamic properties of fiber-reinforced soils at very small strains is very limited. Toward this end, the dynamic behavior of fiber-reinforced soils is investigated experimentally by conducting Bender Element tests under different confining pressures. The effect of polypropylene fiber reinforcement on the shear wave velocity (Vs), the velocity of the primary wave (Vp), the initial Young’s modulus (E0) and the initial shear modulus (G0) of sand and sand–clay mixtures with varying compositions is examined in this study. The soils were reinforced with five different types of polypropylene fibers having lengths from 9 mm to 50 mm, at fiber contents from 0.5% to 2% by weight of dry soil. The results indicate that the dynamic and the small-strain stiffness parameters of fiber-reinforced soils increase with increasing confining pressure, while also being affected by the soil type, the fiber type, and content. Although fiber inclusion resulted generally in a reduction of the dynamic properties of soils, increases ranging from 5% to 55% were observed in certain soil–fiber combinations in comparison with the unreinforced soils.

Fibers doi: 10.3390/fib14060076

Authors: Safaa Kh Al-Jumaili Zahraa T. S. Al-Salih Abdullah A. Al-Hussein Sundus Khaleel Alfaiz Ibtisam A. Jarih Fareed H. Majeed

The mechanical properties and real-time damage evolution of sustainable concrete (SC) containing 100% recycled concrete aggregate (RCA) under the combined action of hybrid steel and polyolefin fibers were studied. Inspired by solving the massive effects on the environment from construction waste, as well as to improve the lower mechanical performance of lower-grade RCA, the effect of combining high-stiffness hooked-end steel fibers and flexible macro-polyolefin fibers within RCA was investigated. Six different mix designs were considered: plain, single-fiber (100% steel and 100% polyolefin) and three hybrid composites with varying fractions of the steel/polyolefin fibers (25/75, 50/50, and 75/25). Compressive, tensile and flexural strengths were determined by mechanical testing. During compressive testing, the damage evolution was monitored using low-cost acoustic emission (AE) as a non-destructive technique. Cumulative hits analysis, amplitude distributions, and the statistical b-value parameter were used for damage characterization. The results show that steel fiber significantly increased compressive strength (an increase of up to 13.8%), and the 50/50 hybrid mix showed a high synergistic effect, yielding the highest tensile (4.86 MPa) and flexural (25.54 MPa) strengths. AE analysis identified different damage fingerprints: Based on amplitude analysis, steel-fiber composites exhibited high-amplitude events (which may be attributable to fiber pull-out); polyolefin-fiber composites generated medium-amplitude events (may have resulted from distributed microcracking); and hybrid mixes displayed a mixed amplitude distribution. The b-value analysis provided insight into progressive damage and revealed that the hybrid fibers induce stable, diffuse damage that prevents the brittle failure of plain recycled aggregate concrete (RAC). The results show that hybrid fiber reinforcement can be a reliable approach to enhance the mechanical performance and crack resistance of RAC. Furthermore, low-cost acoustic emission (AE) serves as an effective non-destructive method for monitoring damage progression within the material.

Fibers doi: 10.3390/fib14060075

Authors: Savaş Evran Nazmi Ekren Merve Yılmaz Ali Samet Sarkın L. Duta Oğuzhan Gündüz

Non-uniform fiber deposition remains a critical limitation in electrospun poly(lactic acid) (PLA) coating systems. In the present study, experimental characterization was combined with numerical simulations to evaluate the influence of electrospinning parameters on fiber morphology, coating uniformity, and thickness distribution. A 3% PLA solution was electrospun under different processing conditions by varying the applied voltage, needle-to-collector distance, flow rate, and deposition time. The resulting coatings were further analyzed using numerical simulations performed with ANSYS Fluent 2020 R2 software. The results demonstrated that both solution-related and operational parameters strongly influence fiber morphology and spatial deposition behavior. Increasing the applied voltage promoted the formation of thinner fibers; however, excessively high voltage values generated jet instability associated with fiber fragmentation and spray formation. Furthermore, the deposited fibrous layers showed preferential accumulation in the central region of the collector, together with a gradual decrease in coating thickness toward the peripheral areas. A strong correlation was observed between the numerical simulations and the experimental results, confirming the reliability of the proposed modeling approach. Among the investigated conditions, the optimal electrospinning parameters were identified as an applied voltage of 16 kV, a needle-to-collector distance of 17 cm, and a flow rate of 2.5 mL/h. These conditions enabled the formation of homogeneous PLA nanofibers with minimal structural defects and improved substrate adhesion. The combined experimental and numerical approach provides valuable insight into the optimization of electrospinning parameters governing fiber formation and deposition behavior.

Fibers doi: 10.3390/fib14060074

Authors: Jongeok Lee Sung-Jin Lee Woo-Tai Jung

Carbon-fiber reinforced polymer (CFRP) tendons have attracted increasing attention as corrosion-resistant prestressing elements for prestressed concrete and cable-supported structures; however, their practical implementation requires reliable verification of long-term mechanical performance and anchorage reliability. In this study, a 9.5 mm pultruded CFRP tendon and compression-type anchorage system were developed and experimentally evaluated through relaxation, creep rupture, and fatigue tests. The tendon exhibited a tensile strength of 2501 MPa and an elastic modulus of 132.5 GPa. Relaxation tests were conducted at an initial load corresponding to 70% of the ultimate tensile capacity, and the measured relaxation loss after 1000 h was 1.02%. Based on logarithmic regression of the measured data, the relaxation loss at 1,000,000 h was estimated to be 2.11%; however, this value should be interpreted as an extrapolated long-term estimate rather than a directly verified result. Creep rupture tests performed at load ratios of 82.4–100.0% yielded an estimated 1,000,000 h creep rupture load ratio of approximately 80%, although the prediction is subject to uncertainty because of the limited number of specimens and scatter in rupture times. Fatigue tests indicated that the CFRP tendon–anchorage assembly maintained stable performance up to 2,000,000 cycles without measurable degradation in elastic stiffness under the adopted loading conditions. These results suggest that the developed CFRP tendon–anchorage system has promising potential for prestressing applications, while further long-term tests with a larger number of specimens are required to improve the statistical reliability of the extrapolated relaxation and creep rupture predictions.

Fibers doi: 10.3390/fib14060073

Authors: Ana Kalazić Ana Palčić Snježana Brnada Sandra Flinčec Grgac

Surface roughness of woven fabrics plays a key role in tactile comfort and skin–textile interaction, particularly in medical applications involving prolonged contact with human skin. This study focuses on the surface roughness of woven fabrics in plain and twill (1/3 S) weaves intended for hospital bed sheets and bedding applications. Plain weave represents a structurally symmetric system, while twill weave exhibits a pronounced diagonal structure. Roughness was evaluated using the Fabric Touch Tester (FTT) and further analyzed through amplitude (Rq), height distribution (Rku), and frequency-related parameters (linear peak density) obtained by signal processing and peak analysis in OriginPro 2026. The results showed that weave structure is the dominant factor influencing surface topography. Plain weave fabrics exhibited higher amplitude roughness and more uniform height distribution, while twill fabrics showed lower global roughness but stronger directional dependence, particularly in diagonal directions. Linear peak density was not significantly affected by laundering cycles, fiber composition, or finishing, but was strongly dependent on weave type. The findings demonstrate that due to the orthotropic nature of woven fabrics, surface roughness, derived from surface topography, cannot be adequately described by a single parameter, and that a combined analysis of amplitude and spatial descriptors is required, with the surface being evaluated not only along the principal symmetry directions (warp and weft) but also in off-axis directions. These results provide valuable insight for the design of hospital textiles with improved tactile comfort and reduced risk of skin irritation.

Fibers doi: 10.3390/fib14060072

Authors: Herry Chen Tolulope Alayande Mateya Hughes Maxime Daviau Catherine Shrimpton Tyler Hull Daniel Lacroix

Engineered bamboo composites (EBCs) are increasingly considered as sustainable alternatives to tropical hardwoods in structural applications. In jacking systems, performance is primarily governed by compression perpendicular-to-grain (bearing), although improper use may introduce flexural demands. This study evaluates the bearing and flexural behavior of Dragonwood, a commercial parallel strand bamboo (PSB), in comparison to Ekki (Lophira alata) through 120 full-scale tests. Dragonwood exhibited higher mean bearing capacity than Ekki, with yield stresses exceeding those of Ekki by over 60%, indicating strong potential for bearing-dominated applications such as in jacking. However, face-bonded specimens showed sensitivity to glue-line orientation, resulting in flexural strength reductions of up to 42% and undesirable shear failures. Increasing adhesive content and pressing pressure in the manufacturing process did not eliminate this behavior. Single-lift specimens removed the glue-line and showed improved failure behavior in flexure, although with reduced strength. The results demonstrate that manufacturing strategy heavily influences PSB performance. While single-lift Dragonwood products show the most potential, further testing under bearing is required before its suitability for jacking applications can be fully established.

Fibers doi: 10.3390/fib14060071

Authors: Yoshiki Ishida Daisuke Miura Yasuhiro Hotta Akikazu Shinya

This study investigated the effects of 7-day water storage as an accelerated aging condition on the mechanical properties of short fiber-reinforced resin composites (SFRCs) and a bulk-fill resin composite (RC). Two SFRCs (everX Flow Bulk, EXB; everX Flow Dentin, EXD) and one bulk-fill RC (SDR) serving as a control were evaluated. Specimens were stored in distilled water at 37 °C for either 1 or 7 days. Flexural strength, flexural modulus, and Vickers hardness were evaluated. Fractured surfaces were observed using scanning electron microscopy (SEM). For statistical analysis, a two-way ANOVA and Tukey’s test were used (α = 0.05). After 7-day water storage, the flexural strength of SDR significantly decreased (p < 0.05), while SFRCs maintained their initial strength (p > 0.05). In contrast, the flexural modulus significantly decreased in all materials (p < 0.05). Vickers hardness remained unaffected by water storage for all groups (p > 0.05). SEM observation revealed fiber pull-out in SFRCs. Although water immersion induced matrix degradation reflected in a reduced flexural modulus, SFRCs demonstrated promising resistance to initial water aging by maintaining flexural strength after water storage. These findings suggest that SFRCs may be a promising option for biomimetic dentin replacement under short-term hydrolytic aging conditions.

Fibers doi: 10.3390/fib14060070

Authors: Vasilica Popescu Marina Marin Gabriel Popescu Viorica Vasilache Andrei Popescu

Hemp plants are precious resources for the textile industry, being considered a sustainable and more economical alternative to cotton. Sustainable dyeing processes should minimize the consumption of water, energy, and chemicals while ensuring high color intensity and reducing the pollution load of residual baths. Black carrot (Daucus carota L. ssp. sativus) is a valuable source of dyes for dyeing hemp materials because it is rich in anthocyanins and anthocyanidins, which generate colors ranging from red-orange and muted magenta to blue, depending on the pH. In this article, the dye extraction process was colorimetrically monitored for 26 days to determine the optimal fermentation/storage period that generates the most intense color during the dyeing process. The dyeing parameters tested were temperature (40–100 °C), pH (4.33–9.15), duration (1–24 h), concentration (2.5–10%), and the presence of organic acids (ascorbic and citric acids). Virgin baths and the first three residual baths were used in the dyeing process. While the results of FTIR, SEM, and EDX analyses confirmed the dyeing process, the CIEL*a*b* measurements quantified the characteristics of the colors obtained using virgin and residual baths. The 12 principles of green chemistry were also discussed, together with their implementation in hemp dyeing.

Fibers doi: 10.3390/fib14060069

Authors: Qun Li Xufeng Song Longzhan Zheng Guangxi Li Qingqing Lü Liquan Yang Erbo Liu Yuqin Ma Zhoukui Li

Carbon fiber-reinforced polymer (CFRP) composites are in urgent demand in the aerospace, new energy vehicle, and wind power sectors owing to their superior specific strength, specific modulus, and lightweight potential. However, molding defects, such as voids, dry spots, and delamination, arising from their anisotropy and weak interlaminar bonding, severely constrain their service performance. Advanced molding technologies represent the key to overcoming this bottleneck. This paper systematically reviews typical advanced molding technologies in the field of CFRP composites, including resin transfer molding (RTM) and vacuum-assisted resin transfer molding (VARTM) in liquid composite molding, autoclave molding and compression molding (CM) in prepreg molding, and automated fiber placement (AFP) and material extrusion (ME) in automated molding. From an integrated perspective of “technological evolution–process characteristics–defect mechanisms–optimization strategies,” this review summarizes the technical principles, development trajectories, and core advantages of each process, analyzes the formation mechanisms of typical defects, including voids, dry spots, delamination, wrinkles, warpage, and melt instability, and summarizes multidimensional optimization advances in process parameter regulation, numerical simulation, resin modification, equipment upgrading, path planning, and thermal management. Furthermore, the differences and complementarities among these processes in terms of molding precision, efficiency, cost, and applicable scope are compared. Finally, future development directions, including digital twins, green low-carbon manufacturing, ultra-large integrated structures, multi-process integration, standardized defect characterization, and low-cost collaborative design, are discussed. This paper aims to provide systematic theoretical references and technical support for the optimization and upgrading, process integration, and industrial application of advanced CFRP molding technologies.

Fibers doi: 10.3390/fib14060068

Authors: Juan Jurado Victor Huilcapi Ivan Suarez Armando Lopez

This article proposes a sustainable approach to producing eco-friendly paper from fibers derived from water hyacinth (Eichhornia crassipes), an invasive aquatic species with potential high lignocellulose content. The research evaluated the possibility of using its biomass as a non-wood raw material for papermaking through an industrial-oriented processing framework. About 10 groups of water hyacinth samples were analyzed by separating their components (roots, leaves, and stems) to determine moisture content, dry biomass yield, fiber distribution, and performance in papermaking. Mechanical pulping and mild alkaline treatment with sodium hydroxide were compared to evaluate their effects on fiber behavior and paper quality. The results showed a high moisture content in the biomass, averaging approximately 88%, while the remaining dry matter represented the usable fibrous material fraction. After fiber classification, it was revealed that the long fibers predominated over the short fibers and the fine fibers (waste), favoring the hydrogen bonding and structural anchoring during sheet formation. Mechanical quality analyses were conducted using the Corrugating Medium Test (CMT), Concora Crush Test (CCT), Ring Crush Test (RCT), and Short Compression Test (SCT). Untreated water hyacinth paper demonstrated mechanical properties comparable to those of an industrial reference paper, including consistent compression resistance and corrugating performance. In contrast, the alkaline-treated sample showed greater structural uniformity but lower mechanical strength due to fiber fragmentation and increased fine production. Overall, the findings showed that Eichhornia crassipes represents a viable and sustainable alternative to non-wood fibers for paper production, offering potential environmental benefits by serving as an invasive species and reducing dependence on wood-based raw materials.

Fibers doi: 10.3390/fib14060067

Authors: Maciej Kaźmierowski Jakub Sławiński Jarosław Rybak Jolanta Dąbrowska

This study evaluated the effects of copper slag (CS), dosed relative to the mass of fly ash (FA; CS = 0, 7.5, 15, and 22.5%), and the volume fraction of hybrid steel fibers (Vf = 0.0, 0.5, and 1.0%) on the mechanical response of an alkali-activated geopolymer composite. The tests were performed using a two-factor CS × Vf design (4 × 3), with compressive strength (fc) and splitting tensile strength (fct.sp) determined as the response variables. Statistical analysis showed significant effects of CS, Vf, and CS × Vf on fc, and a significant CS × Vf interaction for fct.sp, confirming that the fiber effect depended on the CS content. The greatest increases in fc relative to fiber-free composites were obtained for CS = 7.5%: +73% (Vf = 0.5%) and +102% (Vf = 1.0%), and for CS = 22.5%: +75% (Vf = 1.0%). For fct.sp, a decrease was found at CS = 0% and Vf = 0.5% (−34%), whereas an increase was observed at CS = 22.5% and Vf = 1.0% (+49%). The interpretation of the mechanical response was extended by DIC-based strain analysis in compression and splitting tests, together with σct.sp–εx curves, indicating differences in strain/damage localization and post-cracking response.

Fibers doi: 10.3390/fib14060066

Authors: Lubomír Macků Ondřej Bílek

Carbon-fiber-reinforced polymer (CFRP) components commonly require milling to achieve final dimensional accuracy and surface integrity, yet tool selection remains a trade-off between surface quality, process load, and cost. This study compared two industrial tool concepts for CFRP side milling under matched cutting conditions: a WC-Co compression-type end mill and a PCD end mill. A two-factor central composite design with 13 parameter sets was used, and tool effects were evaluated through paired differences in Ramean, Rzmean, and Fxy,RMS. The PCD tool significantly improved surface quality, with mean paired differences of −2.00 µm for Ramean and −6.67 µm for Rzmean, while increasing Fxy,RMS by 14.86 N relative to WC-Co. Response-surface analysis showed that the roughness advantage of PCD was broadly stable across the investigated process window, whereas the force penalty was nonlinear and was best described by a second-order CCD model (R2 = 0.820, model p = 0.015), with a significant quadratic cutting-speed term. Scenario-based decision analysis further showed that PCD was preferred in 12 of 13 DOE points under quality-driven weighting, whereas WC-Co was preferred in all 13 points under cost-driven weighting. The results indicate that PCD is the preferred quality-oriented solution for CFRP side milling, while WC-Co remains advantageous when lower load or lower cost is prioritized.

Fibers doi: 10.3390/fib14060065

Authors: Victoria E. Santillan Samerender Nagam Hanumantharao Stephanie Bule Ronish M. Shrestha Carter Rodzik Alan Mendoza Estrada Stephen L. Farias Marina Tanasova Smitha Rao

Tissue engineering is widely used in research for investigating cellular proliferation, behavior, and responses to various stimuli. However, the predictive value of preclinical studies using cell culture plates is limited by the inability to recapitulate the complexity of the physiological microenvironment. Synthetic three-dimensional (3D) scaffolds can be engineered to mimic the complex morphology of the extracellular matrix of native tissues and can serve as physiologically relevant platforms for preclinical studies. In this study, 3D electrospun scaffolds were characterized to aid in breast cancer research. Unlike previous studies that focused primarily on scaffold fabrication or cell viability, this work systematically evaluates how scaffold morphology influences breast epithelial and breast cancer cell behavior within three-dimensional microenvironments. Breast cancer cell lines and normal breast epithelial cells were seeded on scaffolds of different morphologies, on commercially available mesh scaffolds, and on standard tissue culture plates. Cells were treated with a fluorescent fructose mimic (ManCou-H) that targets the fructose-specific transporter GLUT5 to assess metabolic activity on different scaffolds. The study evaluated cell–cell and cell–matrix interactions through time-lapse experiments, cell metabolism, and variations in the expression of cytoskeletal protein (CK18) and GLUT5. Statistically relevant differences were observed between cells cultured on scaffolds and plates, and different scaffolds morphologies. Results from this study demonstrate that scaffold topology alone can significantly alter cellular phenotype and metabolic responses, highlighting the importance of scaffold selection in the development of predictive non-animal in vitro models and studies of the tumor microenvironment.

Fibers doi: 10.3390/fib14060064

Authors: Mário F. S. Ferreira Sofia C. V. Latas

Many non-equilibrium phenomena and nonlinear dissipative systems can be described by the complex Ginzburg–Landau equation (CGLE). So far, several types of solutions to the cubic–quintic CGLE have been obtained, which can be mainly classified into two categories: stationary solutions and pulsating solutions. One of the most striking forms of pulsating solutions is the exploding soliton, which belongs to the class of chaotic solutions. In this paper, we review the main properties of exploding solitons, considering the case of passively mode-locked fiber lasers described by the CGLE. The impact of the filter’s spectral response and the possibility of converting exploding solitons into fixed-shape pulses by using a proper combination of some higher-order effects are illustrated. An overview of recent experimental observations concerning exploding solitons in different laser configurations is also provided.

Fibers doi: 10.3390/fib14050063

Authors: Vincenzo Romanazzi Francesco Micelli Sandro Moro Pedro Serna Ros Maria Antonietta Aiello

In recent years, Ultra High-Performance Fiber-Reinforced Concretes (UHPFRCs) have gained significant attention for their applications in structural components, particularly for improving impact resistance and post-cracking behavior. This study explores the behavior of thin Ultra High-Performance Concrete (UHPC) panels reinforced with synthetic fibers, focusing on the potential use of these materials for building façades. Three different synthetic fiber-reinforced mixes were developed, utilizing polyvinyl alcohol (PVA) microfibers, polypropylene (PP) macrofibers, and a hybrid combination of both. These thin, unreinforced panels were subjected to impact testing using a free-falling steel ball to evaluate their mechanical response. The results were analyzed in terms of crack patterns, crack openings, and overall impact resistance. Additionally, numerical analysis was implemented by using the ABAQUSTM finite element code, in order to predict the panels’ performance under impact, providing a comparison between experimental results and numerical simulations. This investigation highlights the significant contribution of synthetic fibers in enhancing the toughness and impact resistance of UHPC panels, demonstrating their viability for structural applications requiring enhanced durability.

Fibers doi: 10.3390/fib14050062

Authors: Mostafa M. Ahmed Mohammed G. El-Gendy Ehab F. El-Salakawy

Interface shear transfer (IST) is a critical mechanism governing composite action in reinforced concrete (RC) structures. While the IST behavior in steel-RC is well established, its application to glass fiber-reinforced polymer (GFRP)-RC remains uncertain due to the scatter of experimental data and the absence of a unified design model. This study assesses the accuracy of current IST design provisions and analytical models for GFRP-RC using a database of 107 push-off tests from the literature, including 56 specimens with an as-cast interface, 20 specimens with an intentionally roughened interface, 26 specimens with a monolithic interface, and five specimens with a smooth interface. Predictions of available models were compared with experimental peak loads. The results show that current provisions in design codes and standards either significantly underestimate or overestimate the IST capacity. The proposed analytical strain-based models in the literature improved predictions but exhibited inconsistencies across different interface conditions. Accordingly, a modified IST model is proposed based on regression analysis, incorporating a cohesion parameter as a function of the concrete strength with a GFRP strain limit of 0.003. The proposed model provides accurate, yet conservative, predictions across different interface conditions.

Fibers doi: 10.3390/fib14050061

Authors: Gabriel Constantinescu Syed Tahir Ali Shah José Paulo Oliveira Santos João Manuel Cardoso Mário Jorge de Sousa Henriques António Manuel de Bastos Pereira

The demand for lower-impact materials in mobility has increased interest in the lightweight composite structures for electric vehicles (EVs). This study presents an extended and revised dataset for biaxial non-crimp fabric (NCF) composite laminates intended for two-wheeled EV chassis applications, building on earlier published results by repeating all mechanical tests and recalculations and by adding a full stress–strain analysis, a repeatability assessment across multiple specimens, and a digital image correlation (DIC)-based strain evaluation. Three material families, represented by four laminate conditions, were investigated: carbon/epoxy composites post-cured for 4 h and 10 h, glass-fiber composites, and linen (flax) composites. The tensile and flexural behaviors were characterized according to ISO 527-4 and ISO 14125, respectively, while a GOM ARAMIS optical system was used to obtain the axial strain, transverse strain, and Poisson’s ratio. Carbon laminates showed the highest performance, with the 10 h post-cure condition reaching 1126 MPa tensile strength, up to 60 GPa Young’s modulus, 696 MPa flexural strength, and 43 GPa flexural modulus. Glass laminates provided intermediate properties, whereas flax laminates showed lower strength but higher compliance and deformation capacity. The obtained results show that the biaxial NCF composites studied in this work offer weight-saving potential for micro-mobility chassis and provide a standard-based benchmark for future durability and life-cycle studies.

Fibers doi: 10.3390/fib14050060

Authors: Zafar Arshad Salman S. Alharthi

The journal retracts the article titled “Enhancing the Thermal Comfort of Woven Fabrics and Mechanical Properties of Fiber-Reinforced Composites Using Multiple Weave Structures” [...]

Fibers doi: 10.3390/fib14050059

Authors: Ana Torre Pedro Espinoza Sorín Ramírez Luisa Shuan

Artificial intelligence (AI) has become a powerful tool for machine-learning-based forecasting from available data. This study evaluates several artificial neural network (ANN) architectures and the traditional multiple linear regression (MLR) method to predict the compressive strength of steel-fiber-reinforced concrete (SFRC). The input parameters considered in the models included electrical resistivity, concrete age, water-to-cement ratio (w/c), and cement content. Fifty-four concrete mixes were designed by varying the w/c ratio (0.45, 0.50 and 0.60), the nominal maximum size of the coarse aggregate (1″, 3/4″ and 1/2″) and the type of metallic fiber (Sika® Fiber CHO 65/35 [F1] and Sika® Fiber CHO 80/60 [F2]). Cylindrical specimens were cured in accordance with ASTM C31 and tested at 7, 14, and 28 days. Compressive strength was determined in accordance with ASTM C39. Electrical resistivity was measured at 7, 14 and 28 days using the Wenner method. Using this dataset, six ANN architectures were trained and the multiple linear regression (MLR) equation was calculated using Matlab R2018a software. The ANN models outperformed the MLR approach in predictive accuracy. Optimal performance was achieved with a three-layer ANN comprising 50 neurons in the first hidden layer, 20 in the second, and a single output neuron. The activation functions used were f(s) = tanh(s) for the first two layers and g(s) = s for the third layer. This ANN architecture achieved a correlation coefficient (R) of 0.98157 and the lowest error metrics, reported as percentages: mean absolute error (MAE), mean absolute percentage error (MAPE), mean squared error (MSE), and root mean squared error (RMSE) of 2.37%, 2.52%, 0.124%, and 3.52%, respectively. These findings demonstrate that ANN models can accurately predict the compressive strength of metal fiber reinforced concrete from electrical resistivity measurements and the variables mentioned above.

Fibers doi: 10.3390/fib14050058

Authors: Chanel Angelique Fortier Michael Santiago Cintron

There is growing concern about the ubiquitous presence of microfibers in waterways, atmosphere, and soil. Thus, the study of microfibers is of interest. Presently, there is no standard method for quantifying microfibers, so the objective of the current study was to employ a Fiber Quality Analyzer 360 (FQA) to examine microfibers with image analysis. In this study, two surfactants, Teric 169 and Surfonic LF-17, have been independently added to synthetic and natural microfiber suspensions to investigate their impact on arithmetic length and fiber count measurements. Herein, it has been observed that surfactants with pulsed sonication were shown to positively impact the synthetic microfibers suspensions, yielding statistically different higher fiber counts compared to the controls. However, the natural microfibers were found to produce fiber counts independent of the surfactant addition when compared to controls. In addition, the arithmetic lengths for polyester and nylon increased compared to a previous study, whereas the acrylic microfibers only changed marginally. Clearly, these results indicated that, with the pulsed sonication and surfactant addition pretreatment to water suspensions of microfibers, the FQA can be used to quickly and easily examine synthetic and natural microfibers in a single research study.

Fibers doi: 10.3390/fib14050057

Authors: Wafa Mahjoub Sarangoo Ukhnaa Jean-Yves Drean Omar Harzallah

Cashmere is recognized as one of the most valuable natural fibers due to its softness, fineness, and valuable properties. However, the production of fine cashmere yarns remains technically challenging due to the intrinsic variability of fiber characteristics and the presence of coarse guard hairs within the fleece. This study investigates the optimization of spinning conditions for the production of fine cashmere yarns by analyzing the influence of fiber preparation and spinning technology on yarn structure and performance. Cashmere fibers with an average diameter of approximately 16 µm were processed through several preparation stages to improve fiber alignment and reduce the proportion of short fibers. Yarns with linear densities ranging from 10 to 12.9 tex were produced using both conventional ring spinning and compact spinning systems. Yarn quality was evaluated through measurements of irregularity, yarn defects, tensile properties, and hairiness. The results indicate that improved fiber preparation significantly enhances sliver regularity and spinning stability, while compact spinning technology reduces yarn hairiness. However, the results also show that residual defects such as neps remain the main limiting factor for spinning performance, even under optimized conditions. The findings highlight the importance of optimizing both fiber preparation and spinning technology to enhance the spinnability and overall quality of fine cashmere yarns.

Fibers doi: 10.3390/fib14050056

Authors: Frederico Barbosa Filipe Miguel Margarida F. Domingues João Carlos Silva

The limited regenerative capacity of articular cartilage (AC) following injury has led to a high prevalence of degenerative AC-related disorders, including osteoarthritis (OA). Current clinical treatments for OA have failed to halt disease progression, driving growing interest in cartilage tissue engineering (CTE) strategies aimed at developing biomimetic substitutes to regenerate damaged AC tissue. Among the available biofabrication techniques, electrospinning has gained attention due to its ability to generate fibrous scaffolds that closely mimic the architecture of the native AC extracellular matrix, while also serving as versatile drug delivery platforms with high surface area and elevated drug loading efficiency. Small molecules, low-molecular-weight therapeutic agents capable of interacting with both cell membrane and intracellular components, can be incorporated into these scaffold systems to target the underlying mechanisms of OA. This review examines the current state of the art of small molecule-loaded electrospun scaffolds for CTE applications. Small molecules targeting pain, inflammation, and cartilage function restoration show considerable therapeutic potential, and their incorporation into coaxial and other advanced electrospinning setups enables controlled and sustained drug release. Recent examples of small molecule-loaded electrospun scaffolds for AC repair demonstrate enhanced chondrogenic differentiation and neo-cartilage formation, supporting their potential as viable CTE strategies. Nevertheless, challenges related to drug release kinetics, scaffold load-bearing properties, manufacturing scalability, reproducibility, and regulatory approval remain critical barriers to clinical translation. Emerging fabrication strategies, AI-assisted optimization, personalized medicine approaches, and stimuli-responsive drug delivery systems offer promising avenues to overcome these limitations and advance the clinical adoption of these platforms.

Fibers doi: 10.3390/fib14050055

Authors: Johnson I. Humphrey Stephen Dobreh Md Mostafizur Rahman Ayomide Sijuade Okenwa I. Okoli

The demand for materials that can operate reliably in extreme environments, including rocket nozzles, re-entry heat shields, sharp leading edges, high-velocity impact, and high-temperature energy systems, continue to drive advances in thermal–structural materials. Carbon/Carbon composites remain a leading baseline because of their low density, high-temperature mechanical retention in inert atmospheres, and excellent thermal-shock tolerance. However, long-term durability is constrained by rapid oxidation in air at elevated temperatures, limited fracture toughness and elastic modulus in many architectures, and high manufacturing cost driven by multi-cycle densification and stringent quality assurance. Consequently, contemporary strategies increasingly rely on modifying Carbon/Carbon composites with ultra-high-temperature ceramics and adopting accelerated or simplified manufacturing routes. This review synthesizes recent progress in the design, manufacture, and application of high-performance modified Carbon/Carbon composite systems for extreme aerospace environments, emphasizing composition/architecture selection, oxidation, and ablation protection, toughening concepts, and cost-aware densification. Because extreme environments performance is governed by coupled aerothermal loading, gas–surface chemistry, internal transport, recession, and thermomechanical response, the review also consolidates the multiscale modeling and software toolchains increasingly used to size thermal-protection systems, interpret experiments, and guide down-selection. Key challenges and future directions are further discussed for reusable materials and validated performances beyond ~2000 °C.

Fibers doi: 10.3390/fib14050054

Authors: Yakubova Dilfuza Turaev Khayit Alikulov Rustam Mukumova Gulvar Norkulov Fayzulla Kholboeva Aziza Ahatov Behzod

Healthcare-associated infections (HAIs) remain a significant global challenge, affecting approximately 7% of patients in developed countries and over 10% in developing regions, according to the World Health Organization. Medical textiles, particularly hospital bed linens and pillowcases, play a critical role in the transmission of pathogenic microorganisms due to their porous structure and moisture-retaining properties, which support microbial survival and proliferation, including bacteria such as Staphylococcus aureus and Escherichia coli. Conventional disinfection methods, including laundering and thermal treatments, provide only temporary protection, leading to rapid recontamination during use. In recent years, various antimicrobial agents and functionalization techniques have been developed to impart long-lasting antiseptic properties to textile materials. However, these approaches differ significantly in terms of antimicrobial efficiency, durability, cost-effectiveness, and environmental impact, making the selection of optimal strategies challenging for practical healthcare applications. This review provides a comprehensive comparative analysis of antimicrobial agents used in healthcare textile functionalization, including metal-based nanoparticles, organic compounds, and bio-based materials. In addition, it evaluates key modification methods such as coating, padding, and in situ synthesis, with particular emphasis on their influence on antimicrobial performance, wash durability, and practical applicability. Furthermore, this review discusses major challenges associated with the use of antiseptic coatings, including toxicity, environmental concerns, and economic limitations. Based on the analysis, promising directions for the development of safer, cost-effective, and durable antimicrobial textile systems are highlighted, offering valuable insights for future research and real-world healthcare applications.

Fibers doi: 10.3390/fib14050053

Authors: Azad Gull Anil Kumar Mysore Nagaraj Thomas Braxton Amit Kumar Dhaneshwar Padhan Rubia Bukhari Swathi Koppa Rameshjois Ravindra Aurade

Non-textile application of silk fiber is the major focus of the present scientific communities. Characteristics, i.e., structural, mechanical, are the key advantages of silk protein to make it promising candidates for its variable application. Keeping this in view, the present investigation has been conducted to understand the structural and mechanical variability of silk breeds, i.e., CSR2 × CSR4 (single hybrid), PM × CSR2 (cross breed) and FC1 × FC2 (double hybrid) for their respective promising non-textile application. It is envisaged that FC1 × FC2 (double hybrid) has the highest tensile strength (431.47 ± 28.46 MPa), Young’s modulus (5.92 ± 0.45 GPa) and β-sheet content (46.62 ± 1.45%). The lowest nano-crystallite size (3.34 ± 0.22) and elongation % (10.85 ± 0.77) were also observed in the FC1 × FC2. Further, significant positive correlation was observed between β-sheet with crystalline % (p *** < 0.001; r = 0.95), crystalline % with tensile strength (p *** < 0.001; r = 0.91) and Young’s modulus with tensile strength (p * < 0.001; r = 0.80). This indicates that the higher the β-sheet content is, the higher the tensile strength and higher crystalline phase of the fiber will be. Crystallite size has a negative correlation with the β-sheet content, crystalline %, tensile strength and Young’s modulus, which shows that the lower the crystallite size, the more the compactness and strength will be.

Fibers doi: 10.3390/fib14050052

Authors: Niwanthi Dissanayake Vidura D. Thalangamaarachchige Edward L. Quitevis Zeyad Zeitoun Noureddine Abidi

This study explores the influence of anion hydrogen-bond basicity, quantified by the Kamlet–Taft β parameter, on cellulose dissolution in imidazolium-based ionic liquids (ILs). A series of ILs sharing the common cation 1-benzyl-3-methylimidazolium were synthesized with varying anions, including chloride, acetate, formate, methoxyacetate, and methylphosphonate. The hydrogen-bond accepting ability (β) of each IL was experimentally determined and correlated with cellulose dissolution performance. Dissolution capability was evaluated by solubilizing 5 wt% cotton cellulose at 90 °C and monitoring under polarized light microscopy. Among the studied systems, 1-benzyl-3-methylimidazolium acetate (β = 1.01) demonstrated the highest dissolution efficiency, highlighting the critical role of strong hydrogen-bond basicity in disrupting the cellulose hydrogen-bonding network. To support the experimental observations, COSMO-RS simulations were conducted to probe the molecular-level interactions between anions and cellulose. Parameters such as anion size, theoretical density, viscosity, and surface charge density distribution were analyzed to elucidate their contributions to dissolution behavior. The regenerated cellulose was further characterized using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy.

Fibers doi: 10.3390/fib14050051

Authors: Maria Concetta Cocchiara María Isabel Prieto Alfonso Cobo Fernando Israel Olmedo

This research aims to study the compressive behavior of concrete with partial replacement of fine aggregate by recycled rubber. In addition, the mechanical capacity of these concretes will be analyzed when reinforced by carbon fibers (CFRP) and basalt (BFRP) confinement. To carry out the work, 48 cylindrical test specimens were made, corresponding to 4 mixes, with different percentages of recycled rubber by volume (0%, 10%, 20%, and 30%). The compressive behavior of unreinforced concrete with and without recycled rubber, reinforced concrete made from concrete with and without recycled rubber previously taken to failure, and reinforced concrete with and without recycled rubber without prior failure were evaluated in order to assess the influence of concrete quality before placing the reinforcement. The results show that replacing fine aggregate with recycled rubber in concrete reduces its strength and stiffness, increasing its ductility, with the optimum replacement percentage being 10%. On the other hand, confining concrete with FRP (BFRP and CFRP) improves its strength and ductility compared to unconfined concrete, obtaining similar values regardless of the initial strength of the reinforcing concrete. Confining concrete with CFRP achieves strength improvements of 26% compared to reinforcement with BFRP.

Fibers doi: 10.3390/fib14050050

Authors: Lahbib Abenghal Dan Belosinschi Hamid Lamoudan Aleksandra Mikhailidi François Brouillette

Natural fibers are among the most extensively exploited bio-based materials in industry due to their abundance, affordability, and biodegradability. However, their intrinsic properties often require improvement through chemical, mechanical, or enzymatic treatments to expand their applications. Phosphorylation is a highly effective chemical modification that enables the covalent grafting of phosphate groups onto the fiber backbone. These functionalities enhance hydrophilicity, anionic charge density, swelling capacity, and water uptake, while significantly improving flame-retardant performance. In addition, phosphorylation can reduce energy consumption and production costs in the manufacture of functionalized micro- and nanofibrillated fibers, as the increased swelling facilitates fibrillation. Consequently, phosphorylated fibers are suitable for water treatment, biomedical devices, construction materials, and other advanced materials. Dozens of reagents and various synthetic routes have been explored to perform this reaction, each producing materials with distinct properties. Phosphorus content remains the primary parameter used to assess modification efficiency. This literature review examines existing phosphorylation methods, including reagents, substrates, and characterization techniques, and discusses applications such as flame retardancy, thermal insulation, ion exchange, energy storage, electrodes, and battery recycling. It also briefly addresses key challenges, including limited hydroxyl accessibility, control of the degree of substitution, potential cellulose degradation, and scalability constraints.

Fibers doi: 10.3390/fib14050049

Authors: Fabíola Martins Delatorre Allana Katiussya Silva Pereira Gabriela Fontes Mayrinck Cupertino Álison Moreira da Silva Michel Picanço Oliveira Damaris Guimarães Daniel Saloni Ananias Francisco Dias Júnior

Polyester resin biocomposites containing biochar have attracted attention for improving mechanical strength and thermal stability while promoting sustainability. The pyrolysis temperature of biochar and its proportion in the polymer matrix are key factors affecting biocomposite performance. This study examined how biochar pyrolysis temperatures (400, 600, 800 °C) and incorporation levels (10, 20, 30 wt.%) influence the physical, chemical, mechanical, flammability, and morphological properties of polyester-based biocomposites. The samples were analyzed for density, water absorption, FTIR, XRD, flexural and tensile strength, ignition time, structural degradation, volumetric loss, and SEM microstructure. Biocomposites with 30 wt.% biochar produced at 800 °C showed the best mechanical properties, with a flexural strength of 95.3 MPa and an elastic modulus of 4417.4 MPa, representing increases of 14.5% and 45.7%, respectively, over the control. FTIR and XRD results revealed decreased aliphatic groups and increased aromaticity at higher pyrolysis temperatures, improving interactions between the matrix and biochar. These biocomposites also demonstrated enhanced thermal stability, with an ignition time of approximately 963 s, delayed structural degradation, and reduced volumetric loss (~19.3%). Overall, pyrolysis temperature and biochar content significantly influence the structural, mechanical, and thermal properties of polyester biocomposites, showing that biochar serves as a sustainable, performance-enhancing component in thermoset polymer matrices.

Fibers doi: 10.3390/fib14050048

Authors: Zahra Gholami Johan Persson Kateryna Liubytska Angeles Blanco Fritjof Nilsson Birgitta A. Engberg

Fibre properties significantly influence paper quality. This study investigates fibre property development along an industrial pulp production line, analysing morphological distributions and rheological behaviour to enhance refining performance indicators. Understanding these developments is critical for optimising resource efficiency and increasing industrial sustainability. Softwood thermomechanical pulp (TMP), from high-consistency (HC) and low-consistency (LC) refining, and bleached hardwood kraft pulp (BHKP) were examined. Fibre morphological properties were characterised using an optical fibre analyser, while suspension rheology was assessed using a pulp viscometer, supported by computational fluid dynamics (CFD) and discrete element method (DEM) simulations. Results demonstrate that fibre property distributions provide deeper insights into refining effects compared to average values alone. Systematic trends showed that HC-refined TMP from the first and second refining stage required significantly greater torque to break the fibrous network and fluidise the pulp compared to pulp that was also LC refined. This indicates that alterations in fibre properties, especially shortened fibre length resulting from different refining processes, govern fibre interactions in the three-dimensional network of the pulp suspensions and, therefore, their flow behaviour. In conclusion, combining morphological distribution analysis with specialised rheological measurements offers a robust tool for better understanding and monitoring mill-scale refining processes, enabling improved process optimisation in pulping and papermaking.

Fibers doi: 10.3390/fib14050047

Authors: Bianca Purgleitner Barbara Liedl Christoph Burgstaller

The global expansion of wind energy increases the need for sustainable recycling strategies for glass fiber-reinforced plastic (GFRP) from end-of-life wind turbine blades (WTB). Mechanical recycling is currently the most economically and ecologically viable technology. This study compares post-industrial (PI) waste from laminate cutoffs and post-consumer (PC) GFRP waste from end-of-life WTBs to investigate the influence of waste origin, pretreatment of shredded GFRP, different particle sizes and various matrix formulations on the tensile modulus and tensile strength of pressed bulk molding compounds produced with virgin epoxy resin. Thermogravimetric analysis showed a fiber content of up to 70 wt.%, but the resin residues on the embedded glass fibers dimmish a sufficient bonding of the new matrix system. Finer GFRP fractions consistently yielded higher tensile modulus and strength, with PI and pretreated PC materials performing best. The findings of this study demonstrate that controlled particle size distribution, impurity removal and optimized resin viscosity are key factors to achieve reliable mechanical performance and enable high-value recycling routes for glass fiber composite waste.

Fibers doi: 10.3390/fib14050046

Authors: Feng Yue Xiaofeng Xue

Fuel vapor can be ignited by lightning through various means, particularly through hot spot formation on fuel tank skins. The wing fuel tank cover and its surrounding outer plates together form part of the aerodynamic shape of an aircraft. The lightning protection design of the fuel system, including wing fuel tank, is of great significance for ensuring the aircraft safety. Based on the Joule heating and implosion effect, the damage response of a composite fuel tank cover subjected to lightning strikes is analyzed in this paper. The adopted method combines electrical–thermal coupling with explicit dynamics analysis. Firstly, a finite element model of the fuel tank cover is established using electrical–thermal coupling elements, and the lightning current impact simulation is carried out under given electrical boundary conditions and thermal boundary conditions. On one hand, the ablation criterion is determined by the Joule heating effect and the sublimation temperature of materials. The thermal damage of composite materials subjected to transient high currents is obtained through transient thermal analysis. On the other hand, special implosion elements are selected according to the temperature distribution obtained from the electrical–thermal coupling analysis. The original composite material model in the implosion region needs to be replaced with a new material model described by the high-explosive material model and the JWL equation of state. The von Mises stress distribution and pressure distribution on the structure after implosion are discussed in detail. The results show that concave pits are formed near the implosion zone. Unlike the thermal damage morphology defined by the ablation criterion, the implosion effect makes the damage distribution deviate from the initial fiber direction of each layer. The implosion dynamic method reveals the internal damage and pit and bulge phenomenon around the lightning attachment area to a certain extent.

Fibers doi: 10.3390/fib14050045

Authors: Pavlo Kryvenko Igor Rudenko Oleksandr Gelevera Oleksandr Konstantynovskyi

The paper deals with the concept of how to regulate structure formation in the interfacial transition zone (ITZ) between the Ordinary Portland Cement (OPC) matrix and basalt to ensure the durability of basalt fiber-reinforced concretes. It has been demonstrated that the alkali–silica reaction (ASR) can be transformed from a destructive (negative) process into a constructive one in OPC concrete through activation by sodium water glass combined with the incorporation of an Al2O3-containing additive, namely metakaolin. Alkaline activation increased the compressive strength of OPC basalt fiber-reinforced concrete by 1.6–1.9 times. The formation of stable zeolite-like hydration products within the Na2O-CaO-Al2O3-SiO2-H2O system promoted self-healing of the ITZ. This resulted in a 5.6-fold increase in ITZ microhardness compared to the cement matrix, as well as transforming expansion into shrinkage of concrete with a final value of 0.01 mm/m after 360 days. The structure-forming processes in the ITZ ensured a 1.14-fold increase in the compressive strength of 180-day alkali-activated OPC basalt fiber-reinforced concrete compared to its 30-day strength, in contrast to a 0.92-fold decrease in the strength of the non-modified OPC analog under conditions accelerating the development of ASR.

Fibers doi: 10.3390/fib14040044

Authors: Nusrat Bibi Imran Ahmad Khan Kashif Javed Asfandyar Khan Tayyab Naveed Mainul Morshed Fiaz Hussain Muhammad Junaid Saleem

This study investigates the fabrication of microcapsules using Nigella sativa (N.S.) oil as the core and alginate as the shell material. The N.S. oil microcapsules were prepared using the sol–gel method with different oil concentrations. The microcapsules were applied to the cotton fabric by the pad–dry–cure method, and their attachment was evidenced by scanning electron microscopy (SEM). Air permeability measurements were conducted for all developed samples, revealing that the sample with 8 g loading of N.S. oil and 4.5 g alginate exhibited a 43% reduction compared to the pristine sample. To further investigate the comfort characteristics of the samples, the functionalized cotton samples were subjected to the water vapor permeability index test. The results yielded an index value of 90, indicating that the encapsulation process preserved the comfort characteristics of the samples. Among the samples, the specimen with an oil concentration of 8 mL displayed the maximum antibacterial performance, achieving a 90% reduction in colony-forming units (CFUs) following quantitative testing protocol. However, the qualitative antibacterial assessment indicates no clear zone of inhibition, but no bacterial growth was observed on the samples. Furthermore, the fabric incorporating the maximum loadings of N.S. oil and alginate capsules exhibited the maximum antioxidant activity of 86.5%. These results underscore the critical role of N.S. oil microcapsules in enhancing the antibacterial and antioxidant properties of cotton fabric, while also revealing a harmony between functional performance and comfort characteristics.

Fibers doi: 10.3390/fib14040043

Authors: Yuan Fan Jiayi Zhang Zhaoqian Li Lingyun Wang Min Tang

Military confined spaces face poor ventilation and severe airborne hazards (toxic gases/particulates), while conventional air purification systems with separate filtration–adsorption units are bulky and hard to miniaturize. Activated carbon fiber paper (ACFP) is a promising integrated filtration–adsorption material, but existing studies lack systematic comparisons of different ACF precursors and rational balancing of adsorption, filtration, and mechanical properties. Herein, ACFPs were fabricated via wet papermaking technology, using two ACFs (rayon-based, RACF, and phenolic-based, PACF) as the adsorptive component, glass wool as a filtration enhancer, and dual-melting-point polyethylene terephthalate (PET) fibers as a mechanical reinforcer. Dynamic adsorption was evaluated via DMMP (a Sarin simulant). Results showed that PACF had a micropore ratio twice that of RACF. Under the optimal formulation (20% glass wool, 30% PET, and 50% ACF), both types of ACFP showed FE0.3 μm ≥ 90%. PACFP outperformed RACFP in comprehensive performance, showing higher adsorption capacity, tensile strength, and filtration quality factor. Both ACFPs exhibited superior bed utilization efficiency (RACFP: 91.3%; PACFP: 86.0%) to granular activated carbon (AC: 82.7%), confirming better dynamic adsorption kinetics. This work provides a rational optimization strategy for ACFPs, offering a lightweight, integrated material for air purification in military confined spaces.

Fibers doi: 10.3390/fib14040042

Authors: Se Jin Kim So Hee Shin Dong Ok Shin Won Jun Lee

Conventional separators for lithium metal batteries suffer from poor thermal stability, flammability, and limited mechanical strength. In this study, we report a self-reinforced aramid separator integrated with Li7La3Zr2O12 (LLZO) via a sodium–naphthalene-based selective dissolution strategy. Controlled partial disruption of hydrogen bonding in copolymerized aramid enables the formation of a hierarchical structure consisting of intact fibers and nanofibrillar networks, thereby providing intrinsic mechanical reinforcement without binders. The separator maintains structural integrity up to ~400 °C and retains over 70% weight at 600 °C, exhibiting self-extinguishing behavior (LOI > 30). Puncture strength is more than three times higher than Celgard®, while LLZO integration doubles the ionic conductivity along with excellent electrolyte wettability. This synergistic design provides a promising route toward intrinsically safe and high-performance lithium metal battery separators.

Fibers doi: 10.3390/fib14040041

Authors: Md Mazedur Rahman Md Ahad Israq Szabolcs Szávai Saiaf Bin Rayhan Gyula Varga

The present study investigates simple cubic lattice structures fabricated through an FDM-based three-dimensional (3D) printing method using wood–polylactic acid (wood–PLA) bio-composite filament and develops a data-driven framework to predict their mechanical response. The design of experiments (DOE) was developed using a response surface methodology (RSM) based on a central composite design (CCD) that was implemented in Design-Expert software (Version 13). During fabrication, four different manufacturing parameters—the layer height, the printing speed, the nozzle temperature, and the infill density—were considered. The compressive strength and compressive modulus were evaluated experimentally, and the corresponding stress–strain responses were examined. The results reveal that the layer height is the most influential parameter, where lower layer heights (0.06–0.1 mm) significantly improve both the compressive strength and the modulus due to enhanced interlayer bonding and reduced void formation. The printing speed and the nozzle temperature also play critical roles, where lower printing speeds (≈40 mm/s) and moderate nozzle temperatures (≈195–205 °C) promote more uniform material deposition and improved interlayer bonding, while higher speeds (≥60 mm/s) and excessive temperatures (≈225 °C) lead to reduced bonding quality and a deterioration in mechanical performance. In contrast, the infill density exhibited a non-monotonic influence, where intermediate levels (around 70%) provided an improved performance under combinations of the low layer height (≈0.1 mm), the low printing speed (≈40 mm/s), and the moderate nozzle temperature (≈195–215 °C), suggesting an interaction-driven effect rather than a purely density-dependent trend. To complement the experimental findings, a machine learning model based on eXtreme Gradient Boosting (XGBoost) was developed using 12,000 data points that were derived from stress–strain curves. The model successfully predicted continuous mechanical responses with errors in the range of 2–8% for unseen specimens, suggesting its capability to capture the relationship between printing parameters and mechanical behavior within the studied design space. Overall, the study highlights that the mechanical properties of wood–PLA lattice structures can be effectively tailored by choosing an appropriate printing parameter control and demonstrates the feasibility of using machine learning to estimate mechanical performance without additional physical testing within the defined parameter domain.

Fibers doi: 10.3390/fib14040040

Authors: Lihui Yin Zhu Yuan

This paper presents a systematic investigation into the long-term mechanical property development, water absorption behavior, and microstructural characteristics of hybrid glass and polypropylene fiber-reinforced concrete (HGPFRC). The findings provided valuable engineering construction solutions for holistically considering the improvement effect of hybrid fibers on concrete performance and for the durability design of concrete materials. The main conclusions of the study are as follows: the water-to-binder ratio (w/b) and the hybrid fiber content significantly influenced the development rate of compressive strength in concrete. Compared to the control group without fibers, the compressive strength of HGPFRC increased more rapidly during the curing stage from 7 to 28 days. HGPFRC with different w/b and fiber contents exhibited significant differences in water absorption rates at various testing stages. In this study, the water absorption of HGPFRC reached 60% to 86% of the total absorption on the first day, 6% to 23% from the second to the fourth day, and 3% to 18% from the fifth to the thirty-first day. Considering the compressive strength, water absorption performance, and microstructure observed via SEM, the optimal mix proportion for the HGPFRC in this study was determined to be a w/b of 0.35 and a hybrid fiber content of 1.8%. The hybrid glass and polypropylene fiber content of 2.7% used in this study exceeded the optimal dosage, and the resulting concrete could not meet engineering construction requirements.

Fibers doi: 10.3390/fib14040039

Authors: Tishager Taye Teriya Hirpa G. Lemu Endalkachew Mosisa Gutema

The objective of this study is to review the literature on the natural resources needed for biodegradable materials underscoring the importance of natural fiber-based composites as a feasible alternative. The review focuses on the pivotal role of natural fiber-based composites in the formulation of industry benchmarks, the challenges associated with application of natural fibers, the application areas, and the mechanical properties as well as the determinants influencing the properties of the composites. The manufacturing methods were discussed and compared. In addition, the study highlights the successful instances where enset fiber-based composites have been adeptly implemented. The study also observed potential areas of future research to improve the performance of enset fiber-reinforced composites including the fabrication techniques and treatments. Hand lay-up and compression molding are the conventionally used composite fabrication methods, while the recent advances in 3D printing for composite fabrication bring new opportunities to solve many of the existing limitations. In addition, most research is currently limited to alkali treatment, whereas other fiber treatment techniques could further improve the mechanical performance by modifying the surface properties and removing the impurities. Moreover, hybridization, orientation of fiber, and addition of nano-particles are observed to have direct impact on the composite properties. The review scrutinizes comprehensive examination of the prevailing landscape and prospective courses for enset fiber applications within the realm of sustainable material science, utilizing diverse processing techniques and applications while pinpointing inherent challenges.

Fibers doi: 10.3390/fib14030038

Authors: Andrea Marangon Elisa Calà Alessandro Bessi Alessandro Croce Enrico Avattaneo Eleonora Cara Giorgio Gatti

In recent years, there has been a notable increase in commercial demand for natural fibers. Consequently, numerous studies have concentrated on formulating innovative industrial production methodologies for natural fibers, with a particular emphasis on the environmental sustainability of production processes. Among natural fiber sources, bamboo has emerged as a leading candidate, attracting considerable interest due to its exceptional renewability, rapid growth, and low cultivation requirements. The contemporary industrial methodologies employed in the extraction of cellulose from bamboo frequently entail the utilization of concentrated solutions of strong acids and bases, often at elevated temperatures and with extended treatment durations. These processes generate highly polluting waste from mineral acids and bases, posing significant environmental challenges and ecosystem damage. In response to the prevailing concerns, there has been a marked increase in the focus on environmentally friendly techniques that combine enzymatic treatments, selective chemical reagents, and optimized mechanical processes. These processes facilitate the extraction of high-quality bamboo fibers, which are suitable for utilization in the textile industry and have the potential to replace synthetic fibers. This work demonstrates the efficacy of methodologies employing more diluted solutions than conventional approaches. Specifically, this study utilizes a weak base, such as NH4OH, in conjunction with hydrothermal extraction. It is therefore possible for dilute weak base solutions to yield natural fibers after a relatively brief period of processing, typically just a few hours.

Fibers doi: 10.3390/fib14030037

Authors: Jinming Zhang Yiyang Xu Dongfang Wang Qian Li

After implantation in vivo, airway stents are prone to negative biological effects, such as platelet adhesion, aggregation, and blood coagulation, which may lead to vascular occlusion and thrombosis. Therefore, when studying the antithrombotic properties of vascular grafts, it is crucial to construct a fiber film-coated airway stent with antithrombotic properties. In this paper, PTFE/TPU fiber film was prepared by emulsion electrospinning, and heparin aldehyde group was modified to covalently graft with the fiber film to obtain heparin-loaded fiber film (Hep-PT fiber film), and a heparin-loaded PTFE fiber film-coated airway stent (Hep-PT fiber film-coated airway stent) was prepared. Covalent grafting improves the stability of heparin and promotes the long-term stable release of heparin. The loading of heparin increases the fiber nodes between the fiber films, increases the friction between the fibers, and improves the mechanical properties and ability of the fiber film to resist external forces. At the same time, the Hep-PT fiber film-coated airway stent exhibits excellent cytocompatibility, making it an ideal candidate system for airway stent materials.

Fibers doi: 10.3390/fib14030036

Authors: Aman Ul Azam Khan Nazmunnahar Nazmunnahar Mehedi Hasan Roni Aurghya Kumar Saha Zarin Tasnim Bristy Abdul Baqui Abdul Md Mazid

Conductive thread is an integral aspect of smart textiles in the domain of electronic textiles (e-textiles). This study unveils the development of twelve distinct variants of conductive threads using the twisting method: the fusion of copper filament with cotton and polyester threads. The threads are coated with a carbon paste solution enriched with dissolved sea salt. The carbon paste is obtained from non-functional dry cell batteries, conventionally categorized as hazardous electronic waste (e-waste), which underscores an economically viable and environmentally sustainable approach. Experiments proved that each variant demonstrates minimal electrical resistance. The lowest resistance, 0.0164 ± 0.0001 Ω/cm, was achieved by Carbon-Coated Cotton Twisted Copper Thread-II. Comparative evaluation with commercially available conductive threads, including Bekaert Bekinox® VN type (12/1x275/100z), indicated comparable or moderately lower resistance values for the developed copper-based threads. Mechanical–electrical stability under bending, twisting, and wash–dry cycles confirmed consistent conductive performance with minimal resistance variation. Practical demonstrations further validated the integration of the threads into fabric-based flexible circuits and wearable electronic systems. These findings demonstrate that twisted copper-based conductive threads derived from sustainable coating materials provide a promising alternative for smart textile and wearable electronic applications. Future research should focus on scalable fabrication, enhanced coating fixation, and long-term durability assessment.

Fibers doi: 10.3390/fib14030035

Authors: Izabela Jasińska Alicja Nejman Beata Tkacz-Szczęsna Sandra Flinčec Grgac

Textile fabrics intended for use in protective clothing, workwear, and uniforms are subjected to repeated high-temperature industrial washing and drying processes. It is evident that due to the rigorous nature of the prescribed preservation conditions, textiles that are currently utilised for this purpose do not contain elastomeric yarns: a consequence of their suboptimal thermal stability. However, elastomers enable garments to better fit the wearer’s figure and enhance safety and comfort during occupational activities. Currently, no investigations of EOL (elastolefin) yarn elastic durability under commercial maintenance conditions have been conducted. The publication evaluates the elastic properties and pilling resistance of fabrics with EOL-core weft yarns before and after repeated industrial washing under conditions that are typical of rental use. Additionally, an analysis using SEM, FTIR spectroscopy, thermal and thermogravimetric techniques of core-yarns and the core itself was performed. The tested fabrics retained a high elasticity index, even after 100 industrial washing cycles, as confirmed by instrumental analysis. In conclusion, fabrics with EOL-core yarns can be used for garments that are subjected to intensive maintenance in industrial washing conditions without losing their elastic properties.

Fibers doi: 10.3390/fib14030034

Authors: Karolina Lipska Izabela Betlej Agnieszka Laskowska Piotr Boruszewski

The development of composite materials based on post-consumer polymers and agricultural residues is a pragmatic valorization approach that extends the lifetime of materials. This research aimed to analyze the selected physical and mechanical properties of post-consumer-polyethylene-based composites with lignocellulosic fillers. This study explores the ‘ready-to-use’ valorization of untreated oilseed pomaces. The polyethylene ratio was set at 30% and 40%. Wood particles were substituted with oilseed pomace from nigella, rapeseed and evening primrose. The content of the pomace replacing wood particles was 30%, 65% and 100%. The composites made of post-consumer polyethylene and wood particles were used as a reference. The manufacturing process utilized a hybrid approach, combining extrusion with flat pressing. Increasing pomace content generally reduced the modulus of rupture and modulus of elasticity. Surface roughness decreased with higher pomace addition, except for the 30% rapeseed content for the lower polyethylene ratio, i.e., 30%, which showed unusually high roughness. Higher pomace content improved surface wettability, particularly for nigella-based composites. Water absorption and thickness swelling after 2 h and 24 h of soaking were highest at 30% pomace content and decreased with increasing substitution levels. Evening primrose composites consistently exhibited the lowest water uptake and swelling.

Fibers doi: 10.3390/fib14030033

Authors: Beata Anwajler Krystian Grabowski Tullio de Rubeis Monika Nowakowska Paweł Leśniewski Jacek Kasperski

Construction technologies and materials engineering are collaborating to develop new solutions that enhance energy efficiency. One such solution is thermal barriers filled with phase change material. Thanks to their thermal properties, these innovative barriers are being used in an increasing number of construction projects. Additive manufacturing enables the production of architected thermal barriers with controlled cellular topologies and customized heat transfer pathways. This study investigates the thermal performance of lightweight partitions produced using masked stereolithography (m-SLA) 3D printing, focusing on two geometries: open-cell Kelvin structures and closed-cell honeycomb structures. Two strategies for incorporating phase change material were evaluated: direct addition of 10% and 30% paraffin oil by weight to the photopolymer resin and post-print filling of cellular voids with a PCM-based gel. The aim was to establish the effect of topology and PCM distribution on steady-state thermal parameters and transient temperature stabilization. Experimental testing under cyclic heating–cooling conditions revealed that increasing paraffin oil content significantly improves thermal performance. The open-cell Kelvin structure with 30% PCM exhibited the lowest thermal conductivity (λ = 0.0289 W/(m·K)) and the highest thermal resistance (R = 0.697 m2·K/W). Honeycomb structures achieved λ = 0.0360 W/(m·K) and R = 0.590 m2·K/W at the same PCM content. Transient analysis demonstrated enhanced temperature stabilization, with maximum ΔT values of 29.55 K (30% PCM) and 28.61 K (honeycomb 30%). These results confirm that the geometry produced by additive manufacturing plays a decisive role in governing heat transfer and latent heat utilization in PCM-based thermal barriers.

Fibers doi: 10.3390/fib14030032

Authors: Mária Petková Marcela Hricová Viera Jančovičová Zita Tomčíková Anna Ujhelyiová

This work presents the preparation and obtained results of the properties of biodegradable-oriented systems of dyed polymer by biocolorants in mass. The oriented systems (films) were prepared from biodegradable material Nonoilen. Our applied research is focused on preparing masterbatches using inorganic, organic, and food-nature pigments to prepare films as packaging materials. Inorganic pigments, such as iron and titanium oxide, and organic pigments were selected to maintain the biodegradability of the polymer mixture, as the manufacturer declares the biodegradability of the selected pigments. The food-natural pigments are extracted from plants and food pigments, such as chlorophyll, caramel, and violets. First, rheology was evaluated to verify the processing conditions of the materials, and then the properties of the prepared films were examined. Mechanical properties, supermolecular structure, and coloristic properties were assessed for the pure and dyed films. We investigated color fastness after accelerated thermal-light aging using Q-SUN equipment. Food-nature pigments showed sufficient colorability after preparation, although the coloration was lost relatively quickly after accelerated light aging. If they are used as food packaging materials, these pigments would be highly safe for health, in addition to being biodegradable. The color stability of inorganic and organic pigments reached high stability values even after accelerated aging.

Fibers doi: 10.3390/fib14030031

Authors: Askar Abdykadyrov Amandyk Tuleshov Nurzhigit Smailov Zhandos Dosbayev Sunggat Marxuly Yerlan Tashtay Gulbakhar Yussupova Nurlan Kystaubayev

In recent decades, the reliability and safety of large engineering structures have become a critical issue due to failures caused by undetected micro-level deformations. Fiber-optic strain sensors, especially Fiber Bragg Grating (FBG) and interferometric systems, are widely used in structural health monitoring (SHM); however, their standard sensitivity is often insufficient for early detection of nano-strain level damage. This paper presents a comparative analysis and system-level optimization of the main sensitivity enhancement methods, including mechanical amplification, functional coatings and composite embedding, interferometric schemes, and advanced spectral signal processing. Analytical modeling and numerical simulations were performed. It is shown that flexure-beam amplifiers provide a stable sensitivity gain of 2.1–4.8, whereas lever-type mechanisms achieve higher amplification (5.6–9.3) at the cost of dynamic degradation. Functional coatings increase the strain transfer coefficient from 0.62 to 0.68 to 0.91–0.97, but introduce temperature-induced errors up to 1.5–2.0 µε. Interferometric systems can detect strains at the 10−8 level but exhibit high temperature cross-sensitivity. Advanced spectral processing reduces the Bragg wavelength estimation error by 8–15 times, improving the equivalent strain resolution to (2–5) × 10−8. Based on these results, an optimized integrated approach combining moderate mechanical amplification (2.5–3.5), improved strain transfer (η ≈ 0.85–0.92), and efficient spectral processing is proposed. This improves the equivalent strain resolution from 1 × 10−6 to (1.5–3.0) × 10−8 while keeping temperature-induced errors within 15–25% and limiting the computational load increase to 2–3 times. The proposed solution is suitable for long-term monitoring of large engineering structures.

Fibers doi: 10.3390/fib14030030

Authors: Eduardo J. Mezquida-Alcaraz Juan Navarro-Gregori Pedro Serna

This study presents a reliable methodology for analyzing reinforced ultra-high-performance fiber-reinforced concrete (UHPFRC) elements by linking material behavior to structural performance. A non-linear finite element model (NLFEM) is proposed to simulate the tensile response of reinforced UHPFRC elements, with particular emphasis on shrinkage effects. The model operates in two phases: the first simulates shrinkage during specimen storage and the second simulates the mechanical tensile test, using the internal stresses from the first phase as initial conditions. The model was validated through an experimental program involving reinforced UHPFRC ties. The NLFEM accurately reproduced the load–displacement response using average UHPFRC tensile parameters obtained from a simplified Four-Point bending test Inverse Analysis method (4P-IA). It reliably predicted the shrinkage strain range and its impact on stiffness loss during microcrack initiation and stabilization, where tension-stiffening behavior is critical. Additionally, the simulation from the model captured the transition from microcracking to macrocrack formation and the role of fiber bridging in maintaining stiffness. The predicted shrinkage strain aligns with values reported in the literature and represents a conservative upper bound, neglecting the potential effects of creep and relaxation. Overall, the NLFEM effectively simulates the full tension-stiffening behavior of reinforced UHPFRC, including three-dimensional effects, and provides a reliable tool for structural analysis and design.

Fibers doi: 10.3390/fib14030029

Authors: Matthew Davidson Ryan Graunke Aidan Green Hayden Haelsig Laura Heinemann Subin Antony Jose Pradeep L. Menezes

Carbon Fiber-Reinforced Polymer (CFRP) composites represent a transformative class of structural materials, combining low density, high specific strength, and excellent fatigue resistance. This review provides a comprehensive overview of CFRPs, addressing their structure, manufacturing routes, mechanical performance, and functional behavior, with particular emphasis on damage tolerance, tribological properties, and environmental durability. The discussion begins with the classification and morphology of carbon fibers, highlighting their influence on composite anisotropy and interlaminar behavior. The effects of impact loading, delamination, and environmental conditioning on residual strength and fatigue life are then examined, with reference to established evaluation methods such as ASTM D7136 and compression-after-impact (CAI) testing. From a tribological perspective, the incorporation of nanoscale additives, such as graphite nanoplatelets and TiO2 nanoparticles, and their contribution to enhancing wear resistance by promoting the formation of stable tribofilms, is explored. Advances in processing techniques, including low-pressure curing and improved resin systems, are also discussed for their roles in enhancing manufacturability and energy efficiency. Overall, the review underscores that optimal CFRP performance is achieved through the synergistic integration of fiber architecture, matrix design, and precise processing control, while future progress in nanomodification, recycling, and sustainable curing technologies is expected to further expand CFRP applications in the aerospace, automotive, and high-performance engineering sectors.

Fibers doi: 10.3390/fib14030028

Authors: Yingying Tao Yanmei Zhang Chuan Zhao Changlei Bu Rui Zhang Qikai Wang Qingzhe Yi Fuxin Wu Yanchang Zhu Yongxiang Fang

High-strength concrete (HSC) is vital for large-scale tunnel infrastructure; however, its durability is often compromised by rigorous freeze–thaw cycles in cold-region environments. This study investigates the synergistic effects of incorporating hybrid steel fiber (SF) and polypropylene fiber (PPF) to enhance the frost resistance of HSC. Experimental testing involved 125 freeze–thaw cycles across various fiber dosages and lengths, monitoring mass loss and the relative dynamic modulus of elasticity. Additionally, a concrete damage plasticity (CDP) model was utilized in numerical simulations to analyze thermal stress distribution and damage evolution under coupled freeze–thaw and axial loading. Results indicate that the hybrid fiber integration significantly improved durability, with Group A3 (35 kg/m3 SF and 1.5 kg/m3 of 18 mm PPF) achieving the highest performance. After 125 cycles, Group A3 maintained a relative dynamic modulus of 94.5% and restricted mass loss to 1.42%, a 41% improvement over the fiber-free control. Numerical simulations corroborated these findings, demonstrating that the dual-fiber system preserves load-bearing capacity, limiting compressive strength degradation to just 6.7%. These findings quantitatively validate the synergistic mechanisms of hybrid fibers, providing a robust reference for designing high-durability concrete in cold-climate engineering applications.

Fibers doi: 10.3390/fib14020027

Authors: Sana Ullah Salvatore Benfratello Carmelo Sanflippo Luigi Palizzolo

The rising environmental concerns over cement-based construction materials have led to the development of sustainable alternatives. Among these, geopolymers represent a promising class of low-carbon binders offering environmental benefits and competitive mechanical properties; however, their intrinsic brittleness limits their tensile and post-cracking performance. This study investigates the adoption of flax fibers as natural reinforcement to enhance ductility and post-peak behavior of metakaolin-based geopolymers. The performance of metakaolin-based geopolymers with flax fibers (MKFLAX) was experimentally evaluated in terms of strength, stiffness, toughness, and failure behavior. The addition of flax fibers enhanced ductility, toughness, and post-peak load-carrying capacity while slightly improving stiffness due to the bridging of cracks and the fiber pull-out mechanism. In comparison with the available literature on sisal, flax, and jute fibers, flax fibers showed improved performance due to the better dispersion within the matrix and higher tensile modulus. These findings highlight that flax fiber-reinforced metakaolin geopolymers show enhanced post-cracking behavior at the laboratory scale and could be of interest for sustainable cementitious materials, subject to further validation at the structural scale. Furthermore, a nonlinear finite element model was adopted based on damage mechanics to simulate the damage localization, stress–strain response and post-peak behavior of geopolymer composites. The numerical results showed a reasonable agreement with the experimental trends, particularly in the elastic and early softening phases. The findings are limited to the studied material system, fiber content, and small-scale samples and should be viewed as trend-level observations rather than generalized performance claims.

Fibers doi: 10.3390/fib14020026

Authors: Chunquan Hong Jincheng Wen Huailiang Liu Libo Wang Lin Zhang Xiuquan Ma

Laser slicing of 4H-SiC wafers offers high efficiency and minimal material loss. While nanosecond lasers are the preferred light source, simultaneously achieving high output power, excellent beam quality (M2 < 1.3), and broad operational tunability remains an outstanding challenge. This study developed a highly efficient nanosecond laser source using hybrid fiber and solid-state multi-stage amplification architecture. With excellent beam quality (M2 < 1.3), it achieves the highest output power, widest continuously tunable pulse width range, and broadest repetition rate range currently reported for 4H-SiC laser slicing. This advancement is poised to advance the continued development of 4H-SiC slicing technology.

Fibers doi: 10.3390/fib14020025

Authors: Buda Rocco Pucinotti Raffaele

The seismic vulnerability of existing reinforced concrete buildings is often exacerbated by the inadequate mechanical performance of non-structural components, such as masonry infill walls, which may exhibit brittle behavior and limited deformation capacity under seismic actions. This issue highlights the need for innovative and compatible strengthening materials capable of improving ductility and damage tolerance while maintaining adequate mechanical strength. This study presents an experimental investigation aimed at developing a sustainable fiber-reinforced plaster manufactured exclusively from locally sourced natural materials from the Calabria region, including cork granules, broom fibers, and natural hydraulic lime. Following a preliminary experimental phase, the mixture containing 30% cork granules was selected as the reference matrix due to its favorable mechanical performance and deformability. In the present phase of the research, several composite formulations incorporating broom fibers were produced and experimentally characterized. Uniaxial tensile tests were conducted on broom fibers to assess their reinforcing potential, while compressive and flexural tests were performed on the plaster matrices. The experimental results show that the incorporation of broom fibers significantly enhances flexural behavior and post-cracking ductility, while maintaining compressive strength levels compatible with structural retrofit applications. The study demonstrates that the combined use of cork and broom fiber effectively enhances the mechanical performance of the plaster by promoting ductility, improving flexural behavior, and limiting crack initiation and propagation. The high tensile strength of the fibers promotes effective crack-bridging mechanisms and improved energy dissipation capacity. Overall, the combined use of cork aggregates and broom fibers results in a mechanically balanced plaster composite characterized by enhanced deformability and reduced brittleness. These features make the proposed material particularly suitable for the strengthening of masonry infill walls and for applications where improved ductility and damage tolerance are required, such as seismic retrofitting and restoration of existing buildings.

Fibers doi: 10.3390/fib14020024

Authors: Ramia Almohamad Jean-Yves Drean Laurence Peschel Omar Harzallah

This study evaluates the textile potential of five underexplored Agave varieties (Agave salmiana crassispina, A. salmiana salmiana, A. ingens marginata, A. tecta, and A. mapisaga) through combined analyses of extraction behaviour, microstructure, and single-fibre mechanical performance. Fibres extracted from basal, middle, and upper leaf sections were characterised using scanning electron microscopy (SEM) and single-fibre tensile testing under controlled conditions. All varieties produced spinnable fibres and exhibited significant longitudinal variability in mechanical behaviour along the leaf axis (p < 0.05). Mechanical performance depended strongly on both species and leaf position, with fibres from the middle leaf section generally showing higher tenacity. Variations in Young’s modulus reflected differences in fibre maturity and internal microstructural organisation. Fractographic observations revealed predominantly brittle fracture with microfibrillar rupture and longitudinal fibrillation. Overall, the results demonstrate that agave species and leaf position are key parameters governing fibre performance. These agave varieties therefore represent promising candidates for sustainable textile applications, provided that appropriate fibre selection and blending strategies are implemented to ensure homogeneous yarn properties.

Fibers doi: 10.3390/fib14020023

Authors: William G. Davids Aidan G. McGlone

In this paper, the impact of shear deformations on the load–deflection response of transversely loaded inflatable panels made from drop-stitch fabric is explored. A nonlinear shear constitutive model was derived from torsion tests and integrated into Timoshenko beam theory to predict deflection components. Four-point bend tests of the same panel are conducted at pressures of 34.5, 68.9, and 103 kPa and for span-to-depth ratios of 7.2, 12.5, and 17.8 to give load–deflection response with varying levels of shear deformation. Analytical, mechanics-based expressions are derived to quantify load–deflection response due to bending and shear, including deflections caused by the drop-stitch yarns. The resulting expressions are shown to predict the measured load–deflection behavior to within 20% at the theoretical wrinkling load while indicating that the midspan deflection caused by shear deformations including the effect of the drop-stitch yarns are 78% of the total panel deflection for the lowest inflation pressure and smallest span-to-depth ratio. An approach to reducing panel shear deformability through the incorporation of braided sidewalls is proposed, and a second panel with this modification is fabricated and tested in four-point bending to experimentally demonstrate effectiveness. For the smallest span-to-depth ratio, shear stiffening reduced panel midspan deflection by 17–22% depending on inflation pressure.

Fibers doi: 10.3390/fib14020022

Authors: Chloe M. Taylor Lucian A. Lucia

Stimuli-responsive textiles are a rapidly evolving class of functional fiber-based materials that sense and adapt to environmental triggers. Within these enabling technologies, hydrogels and microcapsules are very illustrative, as they offer complementary mechanisms for moisture management, controlled release, and adaptive performance. Hydrogels provide soft, water-rich polymer networks with modifiable swelling, permeability, and mechanics, while microcapsules offer protection and targeted delivery of active agents through engineered shell structures. When integrated into fibrous networks, they impart dynamic detection responses for moisture, temperature, pH, mechanical stress, light, and chemical or biological agents. This review critically examines progress in design, synthesis, and textile integration of hydrogel- and microcapsule-based systems, with emphasis on materials that exhibit stimuli-responsive behavior rather than passive or extended-release functionality. Strategies for incorporating bulk hydrogels, micro- and nanogels, and stimuli-responsive microcapsules into fibers, yarns, and fabrics are discussed in addition to applications such as smart apparel, medical and hygienic textiles, controlled drug delivery, antimicrobial fabrics, and adaptive filtration media. Existing challenges for durability, washability, response kinetics, scalability, and sustainability are highlighted, while future research directions are proposed to advance the development of robust and intelligent textile systems at the nexus of soft matter science and fiber engineering.

Fibers doi: 10.3390/fib14020021

Authors: Juro Živičnjak Antoneta Tomljenović Igor Zjakić

During use, the surface of textile fabrics is prone to wear, which can cause changes such as pilling. Pilling (entanglement of fibers) is primarily assessed using the standard visual method EN ISO 12945-4:2020, but it can also be quantitatively measured by instrumental methods with image analysis software. Due to non-uniform digital imaging conditions, such as variations in magnification and analyzed surface area, the assessed area is often inconsistent. As a result, the total percentage of the fabric specimen surface area covered with pills is often omitted. To ensure uniform digital imaging, an innovative apparatus was designed and constructed in this research and applied to woven fabrics made from 100% cotton, wool, viscose, polyamide 6.6, polyester, and acrylic fiber. Pilling in the fabric specimens was induced by rubbing with the Martindale pilling tester (EN ISO 12945-2:2020) using two different abradant materials, through predefined pilling rubs ranging from 125 to 30,000. Pilling assessment was conducted using both the visual method and the improved instrumental method, following established grading classes based on the total percentage of the fabric specimen surface area covered with pills. The research results highlight the importance of uniform digital imaging and digital grading, as these demonstrate the high comparability of pilling grades assigned by the standard visual method while providing better distinction between consecutive grades.

Fibers doi: 10.3390/fib14020020

Authors: Paula Vigón Antonio Argüelles Miguel Lozano Jaime Viña

One of the most critical damage modes affecting the structural performance of traditional composite materials, and therefore their durability, is the occurrence of interlaminar cracks (delamination), which are prone to grow under different loading conditions. In this study, the feasibility of repairing carbon fiber reinforced polymer (CFRP) laminates using structural adhesives was experimentally investigated by evaluating the Mode I interlaminar fracture toughness. Two unidirectional AS4 CFRP systems were analyzed, manufactured with epoxy 8552 and epoxy 3501-6 matrix resins. Mode I delamination behavior was characterized using Double Cantilever Beam (DCB) specimens. Three commercial structural adhesives were used in the repair process: two epoxy-based systems, (Loctite® EA 9460™, manufactured by Henkel adhesives (Düsseldorf, Germany), and Araldite® 2015 manufactured by Huntsman Advanced Materials (The Woodlands, TX, USA) and one low-odor acrylic adhesive, 3M Scotch-Weld® DP8810NS manufactured by 3M Company (St. Paul, MN, USA). Adhesive joints were applied to previously fractured specimens, and the results were compared with those obtained from baseline composite specimens. The results indicate that repaired joints based on the 8552 matrix exhibited higher strain energy release rate (GIc) values, approaching those of the original material. The 3501-6 system showed increased fiber bridging, contributing to higher apparent fracture toughness. Among the adhesives evaluated, the acrylic-based adhesive provided the highest delamination resistance for both composite systems.

Fibers doi: 10.3390/fib14020019

Authors: Chao Du Yali Zhao Yong Li

In this study, the process of preparing ABS-ZnO (Acrylonitrile Butadiene Styrene-Zinc Oxide) composite materials as FDM printing materials was elaborated, and the influence of printing process parameters on the tensile properties and surface roughness of the materials was analyzed. It was concluded through orthogonal experiments that among all the parameters studied, the infill rate had the most significant effect on the tensile strength, followed by layer thickness and layer width, while the printing speed had the least effect. When the printing parameters were set as follows: infill rate (90%), layer thickness (0.2 mm), layer width (0.4 mm), and printing speed (200 mm/s), the tensile strength of the sample reached the maximum value of 48.37 MPa. Scanning electron microscopy (SEM) analysis revealed that a high infill rate could make the internal structure of the material denser and the bonding between fibers more sufficient. In contrast, with the increase in layer thickness and layer width, the internal structure of the material exhibited a porous morphology, which led to a decrease in tensile properties. By investigating the effects of printing temperature and layer thickness on the surface roughness of the samples, the optimal surface roughness was achieved when the printing temperature was set at 230 °C, and the layer thickness was 0.3 mm.

Fibers doi: 10.3390/fib14020018

Authors: Mohammad A. Abdul Qader Shannon Hughes Dryver Huston Mandar M. Dewoolkar

This study evaluates the mechanical properties and durability of novel self-shrinking chitosan fibers incorporated into a High-Performance Concrete (HPC) matrix. The cementitious system comprised a 75–25% blend of Portland Limestone Cement (PLC) and Ground Glass Pozzolan (GGP). Two variants of chitosan—food-grade and high-grade—were processed into fibers and integrated at dosages of 0.36%, 0.73%, and 1.45% by weight of binder, alongside a 0% control group. The experimental program assessed eight distinct mixtures through extended freeze–thaw testing (up to 602 cycles), electrical resistance monitoring, and compressive strength evaluation at 56 and 90 days. Results indicated that food-grade chitosan fibers caused a substantial reduction in compressive strength, ranging from 40% to 70% depending on the dosage. Despite this mechanical loss, these mixtures showed localized improvements in freeze–thaw resistance and electrical resistivity. Conversely, the high-grade chitosan fibers exhibited severe performance degradation under freeze–thaw cycling; all reinforced groups fell below 80% relative dynamic modulus, with two mixtures dropping below the 60% failure threshold. In comparison, the control mixture retained 98% of its dynamic modulus after 602 cycles. Ultimately, the findings suggest that, in their current formulation, self-shrinking chitosan fibers do not provide consistent or reliable enhancements to the structural integrity or durability of high-performance concrete.

Fibers doi: 10.3390/fib14020017

Authors: Duman Dyussembinov Zhanbolat Shakhmov Rauan Lukpanov Assel Jexembayeva Adiya Zhumagulova

The article examines the waste management challenges associated with basalt fiber-based mineral insulation materials generated during the production of thermal insulation products. In response to the environmental and economic issues linked to their disposal, a chemical processing approach is proposed to convert this waste into a mineral powder suitable for construction applications, particularly as an additive in asphalt concrete. A detailed technological scheme of the chemical treatment process is presented, and the optimal proportions of waste, water, and electrolyte (sulfuric acid), along with the corresponding processing conditions, are identified. The chemical and mineralogical composition of the raw materials and the resulting powder are investigated, and laboratory tests are carried out confirming its suitability as an active mineral additive. The chemical and mineralogical characteristics of the raw waste and resulting product are analyzed using XRD, SEM-EDS, and standard physical tests. In addition, the proposed technology provides a notable reduction in waste volume, thereby decreasing the load on landfills and contributing to more sustainable resource utilization.

Fibers doi: 10.3390/fib14020016

Authors: Dong-Kyu Kim Woong Han Young Chul Choi Kwan-Woo Kim Byung-Joo Kim

The wettability of a carbon fiber surface is an important factor that determines the strength of its bonding with matrices, and hence, an optimized criterion is required to accurately measure the wettability. In this study, the Washburn capillary rise method was used to select the capillary constant with the minimal deviation among various carbon fiber lengths, and it was applied to determine the contact angle and surface free energy of each carbon fiber length according to the wetting liquid. The smallest deviation in the contact angle was observed for a carbon fiber length of 2 inches, and this observation was attributed to the pores in the fibers and the orientation of the carbon fibers packed inside the column. By reducing the number of pores and achieving favorable packing, the surface free energy of carbon fibers can be measured with a high degree of accuracy, contributing to an improved understanding of fiber–matrix interactions.

Fibers doi: 10.3390/fib14010015

Authors: Faisal Abedin Emiel DenHartog

The interaction between moisture and textile materials plays a critical role in transient thermal comfort, particularly through the exothermic heat released during wetting. While the heat of wetting has been extensively characterized at the fiber level, its behavior in finished fabrics, where structure, porosity, and air gaps influence moisture uptake, remains poorly understood. This study quantifies the heat of wetting of clothing fabrics using a TAM Air isothermal microcalorimeter under controlled isothermal conditions (23 °C). Five fabric types representing different fiber chemistries (Merino wool, cotton, viscose, and polyester) were evaluated in both folded and dissected forms to assess the influence of sampling methods. Wool fabrics exhibited the highest heat release, followed by viscose and cotton, whereas polyester showed negligible exothermic response due to its non-hygroscopic nature. Overall, fabric-level heat of wetting values were lower and more variable than the corresponding fiber-level values reported in the literature, reflecting the combined effects of fabric structure, air permeability, surface hydrophilicity, and sampling uniformity. These findings demonstrate the feasibility and limitations of isothermal microcalorimetry for characterizing moisture–fabric interactions and highlight the need for improved sampling and measurement protocols to more accurately capture fabric-level sorption heat relevant to clothing comfort.

Fibers doi: 10.3390/fib14010014

Authors: Luigi Madeo Anastasia Macario Federica Napoli Pierantonio De Luca

Licorice (Glycyrrhiza glabra) is a perennial herb traditionally valued for its aromatic and therapeutic properties. In recent years, however, growing attention has shifted toward the technical and environmental potential of the plant’s industrial by-products, particularly the fibrous material left after extraction. This review integrates botanical knowledge with engineering and industrial perspectives, highlighting the role of licorice fiber in advancing sustainable innovation. The natural fiber obtained from licorice roots exhibits notable physical and mechanical qualities, including lightness, biodegradability, and compatibility with bio-based polymer matrices. These attributes make it a promising candidate for biocomposites used in green building and other sectors of the circular economy. Developing efficient recovery processes requires collaboration across disciplines, combining expertise in plant science, materials engineering, and industrial technology. The article also examines the economic and regulatory context driving the transition toward more circular and traceable production models. Increasing interest from companies, research institutions, and public bodies in valorizing licorice fiber and its derivatives is opening new market opportunities. Potential applications extend to agroindustry, eco-friendly cosmetics, bioeconomy, and sustainable construction. By linking botanical insights with innovative waste management strategies, licorice emerges as a resource capable of supporting integrated, competitive, and environmentally responsible industrial practices.

Fibers doi: 10.3390/fib14010013

Authors: Jack Andrew Cottrell Muhammad Ali D. Brett Martinson D. Lavorato

This study investigates the behaviour of Compressed Earth Cylinders (CECs) and Compressed Earth Blocks (CEBs) during direct compression tests and examines the influence of aspect ratio and the effects of platen restraint. The experimental investigation utilises two soil types and examines the impact of jute fibre reinforcement on the failure mechanism of CECs with aspect ratios ranging from 0.50 to 2.00. Through experimental analysis and numerical modelling, the effects of platen restraint are examined, and a novel hypothesis of intersecting cones is presented. The results show that specimens with a lower aspect ratio exhibited higher compressive strength due to confinement caused by platen restraint. Moreover, this research has derived new aspect ratio correction factors that enable conversion from Apparent Compressive Strength (ACS) to Unconfined Compressive Strength (UCS) of unstabilised and fibre-reinforced CECs. The experimental results indicate that the derived conversion factor of 0.861 allows for the prediction of CEB strength from CEC specimens with an accuracy of 2.7%. Furthermore, the addition of jute fibres at a 0.25% dosage increased the Apparent Compressive Strength across all aspect ratios. The outcome of this research recommends a standard approach to the application of aspect ratio correction factors when interpreting and reporting the compressive strength of CECs and CEBs.

Fibers doi: 10.3390/fib14010012

Authors: Loukia Plakia Adamantia Zourou Maria Zografaki Evangelia Vouvoudi Dimitrios Gavril Konstantinos V. Kordatos Nikos G. Tsierkezos Ioannis Kartsonakis

Hydrogen, as an alternative energy carrier, presents significant prospects for the transition to more environmentally friendly energy solutions. However, its efficient and safe storage remains a challenge, as materials with high adsorbent capacity and long-term storage capability are required. This study focuses on the synthesis and characterization of a composite material comprising carbon fiber and manganese dioxide (MnO2/CFs), for the purpose of hydrogen storage. Carbon fiber was chosen as the basis for the composition of the composite material due to its large active surface area and its excellent mechanical, thermal, and electrochemical properties. The deposition of MnO2 on the surface of carbon fibers took place through two different synthetic pathways: electrochemical deposition and chemical synthesis under different conditions. The electrochemical method enabled the production of a greater amount of oxide with optimized structural and chemical properties, whereas the chemical method was simpler but required more time to achieve comparable or lower-capacity performance. Elemental analysis of the electrochemically produced composites showcased an average of 40.5 ± 0.05 wt% Mn presence, which is an indicator of the quantity of MnO2 on the surface responsible for hydrogen storage, while the chemically produced composites showcased an average of 7.6 ± 0.05 wt% Mn presence. Manganese oxide’s high specific capacity and reversible redox reaction participation make it suitable for hydrogen storage applications. The obtained results of the hydrogenated samples through physicochemical characterization indicated the formation of the MnOOH intermediate. Regarding these findings it may be remarked that carbon fiber/MnO2 composites are promising candidates for hydrogen storage technologies. Finally, the fabricated carbon fiber/MnO2 composites were applied successfully as working electrodes for analysis of the [Fe(CN)6]3−/4− redox system in aqueous KCl solutions.

Fibers doi: 10.3390/fib14010011

Authors: Valeria Indelicato Roberto Visalli Maria Rita Pinizzotto Carmelo Cantaro Rosolino Cirrincione Alberto Pistorio Claudia Ricchiuti Rosalda Punturo

The present review paper focuses on the peculiar environmental and health implications of fibrous amphibole “fluoro-edenite”, a new mineral first reported in Biancavilla (Etna Mount, Sicily, Italy). Its presence has been linked to an unusually high incidence of malignant pleural mesothelioma, as seen from national surveys during 1988–1997, marking the first case study of natural occurrence of fibrous amphibole in a volcanic context. Despite remediation efforts since the cessation of quarrying activities at the “Il Calvario” quarry, the risk of fiber exposure may extend beyond urban areas to surrounding soils and volcanic formation, not fully characterized yet. This review synthesizes relevant existing literature on mineralogical and chemical features of fluoro-edenite, while also enriching current understanding with new observations from optical microscopy, stereomicroscopy, and Scanning Electron Microscopy (SEM). Our analyses reveal the presence of fluoro-edenite amphibole not only in the altered samples but, significantly, within the massive rock samples. This finding expands its known distribution and offers initial consideration on public health implications related to massive lava rock, which crops out. This study highlights the importance of ongoing monitoring, detailed geological surveys, and further research into fiber occurrences and distribution in the volcanic systems, of which Mt. Etna represents the first case of natural occurrences, in order to fully assess their impact on public health.

Fibers doi: 10.3390/fib14010010

Authors: Augustina Sandina Tronac Simona Marcu Spinu Mihaela Dragoi Cudalbeanu Carmen Laura Cimpeanu Alina Ortan

Human health is profoundly influenced by external factors, with stress being a primary contributor. In this context, the digestive system is particularly susceptible. The prevalence of diseases affecting the small intestine and colon is increasing. Consequently, insoluble plant fibers, such as cellulose and hemicellulose, play a crucial role in promoting intestinal transit and maintaining colon health. Lettuce is a widely consumed leafy vegetable with high nutritional value and has been intensively studied through hydroponic cultivation. This study aims to optimize the cultivation conditions and freeze-drying process of Lugano and Carmesi lettuce varieties (Lactuca sativa L.) by identifying the optimal growth conditions, freeze-drying duration, and sample surface area in order to achieve an optimal percentage of insoluble fibers. Carmesi and Lugano varieties were selected based on their contrasting growth characteristics and leaf morphology, allowing to assess whether treatments and processing conditions have consistent effects on different types of lettuce. The optimal freeze-drying parameters were determined to include a 48 h freeze-drying period, a maximum sample surface area of 144 cm2, and growth under combined conditions of supplementary oxygenation and LED light exposure. The optimal fiber composition, cellulose (21.61%), hemicellulose (11.84%) and lignin (1.36%), was found for the Lugano variety, which exhibited lower lignin and higher cellulose contents than the Carmesi variety. The quantification of hemicellulose, cellulose and lignin was performed using the well-known NDF, ADF and ADL methods. Therefore, optimized freeze-dried lettuce powder, particularly from the Lugano variety, presents a high-value functional ingredient for enriching foods and developing nutritional supplements aimed at digestive health.

Fibers doi: 10.3390/fib14010009

Authors: Nikita A. Shutskiy Aleksandr R. Shevchenko Ksenia A. Mayorova Leonid L. Shagrov Andrey S. Aksenov

A promising application of smart materials based on natural polymers is the potential to solve problems related to hemostasis in cases of severe bleeding caused by injury or surgery. This can be a life-threatening situation. Cellulose and its modified derivatives represent one of the most promising sources for creating effective hemostatic systems, as well as for various sensing applications related to disease detection, infection diagnosis, chronic condition monitoring, and blood analysis. The aim of this review was to identify key criteria for the efficiency of cellulose-based gels with hemostatic activity. Experimental studies aimed at evaluating new hemostatic devices were analyzed based on international sources using the PRISMA methodology. A total of 111 publications were identified. Following the identification and screening stages, 20 articles were selected for the final qualitative synthesis. The analyzed publications include experimental studies focused on the development and analysis of highly porous cellulose-based scaffolds in the form of aerogels and cryogels. The type and origin of cellulose, as well as the influence of additional components and synthesis conditions on gel formation, were investigated. Three major groups of key criteria that should be considered when developing new cellulose-based highly porous scaffolds with hemostatic functionality were identified: (I) physicochemical and mechanical properties (pore size distribution, compressive strength, and presence of functional groups); (II) in vitro tests (blood clotting index, red blood cell adhesion rate, hemolysis, cytocompatibility, and antibacterial activity); (III) in vivo hemostatic efficiency (hemostasis time and blood loss) in compliance with the 3Rs policy (replacement, reduction, refinement). The prospects for the development of highly porous cellulose-based scaffolds are not only focused on their hemostatic properties, but also on the development of smart platforms.

Fibers doi: 10.3390/fib14010008

Authors: Razvan Udroiu Paul Bere Katarzyna Biruk-Urban Jerzy Józwik

High-quality drilled holes are critical in thin fabric-reinforced composites used in many industrial applications; however, the influence of woven architecture on drilling performance without a backup plate remains insufficiently defined. This paper introduces the first comprehensive experimental and statistical framework for evaluating unsupported drilling of thin woven glass fiber-reinforced polymer (GFRP) laminates. The framework integrates the effect of support opening width, fiber weight fraction (wf), feed per tooth, and fabric architecture to quantify their combined effects on delamination, cutting forces, and surface roughness. The samples consisted of vacuum mold-pressed GFRP laminates. Drilling tests were conducted on plain and twill-woven plates, and hole quality was evaluated using thrust force, delamination factor, and surface roughness (Sa). A statistical DOE and multifactorial ANOVA were applied to quantify the effects of the main parameters. For plain-woven GFRP, the best results were obtained with a 65 mm support opening width, 45% fiber wf, and 0.04 mm/tooth feed. Plain-woven laminates exhibited lower average surface roughness (Sa ≈ 5.0–6.5 µm) than twill-woven laminates (Sa ≈ 6.0–7.0 µm). The study demonstrates how fabric architecture and drilling parameters jointly influence hole quality in thin GFRP composites, providing practical guidance for manufacturing applications.

Fibers doi: 10.3390/fib14010007

Authors: Hazman Azhari Abdul Rasid Hamid Yusoff Koay Mei Hyie Fatin Hazwani Aiman Izmin Boey Tze Zhou Farrahnoor Ahmad

Empty fruit bunches (EFBs) and kenaf are two abundant sources of lignocellulosic resource agricultural waste with potential as substrates for mycelium-based composites (MBCs). These composites are lightweight, compostable, low-cost, and suitable for packaging applications. However, their performance is highly dependent on the type of lignocellulosic substrate and the processing conditions applied during production. Despite the promising availability of natural fibers, limited research has focused on the drying process that affects the quality of MBCs. This study investigates the effect of different drying times (12, 18, and 24 h) on the physical and mechanical properties of MBCS produced from EFB and kenaf substrates. Following a 20-day incubation period under controlled conditions, the composites were oven-dried and analyzed for mycelial colonization, density measurement, shrinkage, water loss, shore A hardness, impact resistance, and mold growth. The results demonstrated that a drying time of 24 h yielded the best overall performance. Moisture loss (67.00%) and shrinkage (50.70%) increased with longer drying times (24 h), particularly in kenaf-based composites. Extended drying minimized mold contamination and enhanced the structural integrity of the composites. Overall, EFB-based composites achieved the highest Shore A hardness (44.53 HA). These findings show that optimizing the drying time enhances the durability of MBCs, reinforcing their potential as sustainable, biodegradable alternatives to polystyrene and promoting the development of eco-friendly materials.

Fibers doi: 10.3390/fib14010006

Authors: Tommaso Pini Gianluca Ciarleglio Elisa Toto Maria Gabriella Santonicola Marco Valente

Electrospinning of poly(lactic acid) (PLA) commonly relies on toxic organic solvents, which limit its sustainability and biomedical applicability. In this work, a green electrospinning process was developed using dimethyl carbonate (DMC), a biodegradable and low-toxicity solvent, combined with acetone as a volatile co-solvent to promote efficient jet solidification. Three commercial PLA grades were evaluated for solubility and spinnability, and PLA 4043D was identified as the most suitable for DMC and acetone systems. The electrospinning parameters, including solvent ratio, flow rate, and applied voltage, were systematically optimized to achieve stable jet formation and uniform fiber morphology. Under optimized conditions, the process produced continuous, bead-free nanofibers with a mean diameter of ~1 µm and uniform nanoscale surface porosity resulting from differential solvent evaporation. The resulting fibers were characterized in terms of morphology, structure, thermal behavior, and mechanical performance, confirming increased amorphous content, high porosity (about 78%), and tensile strength of ~3 MPa for the selected electrospinning condition. This study demonstrates that DMC-based solvent systems enable a sustainable and potentially biocompatible route, considering the lower toxicity of the solvents employed, offering a green alternative to conventional toxic processes for the fabrication of medical scaffolds.

Fibers doi: 10.3390/fib14010005

Authors: Houzhen Liu Wenzheng Jiang Shaokai Hu Guodong Zhang Weizhuang Yang Shengzong Ci Tianrun Yang Kun Qiao

The extensive application of carbon fibers (CFs) and their composites in aerospace and electronics has established the optimization of their electrical conductivity as a critical research priority. Conventional electrodeposition techniques are limited by CF inherent chemical inertness and low surface energy, which increase the energy barrier for copper deposition, leading to defective coatings and weakened interfacial bonding. This study demonstrated that sodium hypophosphite (NaH2PO2) enhances CF copper deposition efficiency through concentration gradient experiments (0–30 g/L), revealing its modulation of deposition kinetics, crystallographic evolution, and interfacial adhesion strength. Electrochemical analysis showed that NaH2PO2 accelerates initial copper nucleation by reducing activation energy without forming complexes. Increasing its concentration expanded monofilament diameter from 8.55 to 9.26 μm post-deposition, with copper loading rising 28.89%. XRD analysis identified 20 g/L as the optimum for crystallinity, producing maximal grain size (8.27 nm) and predominant (111) orientation. This structure achieved a conductivity of 1.63 × 103 S·cm−1 (55.24% enhancement) and improved breaking force from 13.54 to 14.57 cN. Adhesion tests showed that the 20 g/L group maintained stability comparable to the control. These results suggest that 20 g/L is the preferred concentration balancing conductivity enhancement with mechanical stability. This approach offers a novel strategy for fabricating highly conductive CF composites.

Fibers doi: 10.3390/fib14010004

Authors: Emmanouil Golias Chris Karayannis

In the original publication [...]

Fibers doi: 10.3390/fib14010003

Authors: Le Quang Trung Yuki Takahashi Motoki Haruta Shinji Okazaki Naoya Kasai

This study presents the experimental optimization of an interferometric optical fiber sensor for acoustic emission (AE) detection. The system employs a simple and low-cost structure composed of sensing and reference fibers, enabling interference-based detection without specialized components such as fiber Bragg gratings or Fabry–Perot cavities. A narrowband laser source was selected through comparative experiments for its superior stability and interference performance. The influence of fiber-loop parameters, including the number of turns and the optical-path intensity ratio, was systematically evaluated to clarify their effects on AE sensitivity and frequency response. The experimental results demonstrate that detection performance and bandwidth can be flexibly tuned by optimizing the loop configuration. Finally, the sensor was validated using a tensile test, successfully detecting AE signals in the range of 20 kHz to 1 MHz. The proposed system provides a robust, EMI-resistant, and cost-effective interferometric solution for AE monitoring.

Fibers doi: 10.3390/fib14010002

Authors: Adèle Hue Coralie Buffet Lèna Brionne Johnny Beaugrand Pierre D’Arras Alain Bourmaud Christophe Baley

Along the French-English Channel coast, fibre flax is traditionally cultivated in spring during a short window from March to July. However, increasingly frequent and severe spring droughts, driven by climate change, cast doubt on the sustainability of this practice. One possible adaptation, inspired by the winter cultivation of oilseed flax and tested over several years, involves extending the growing cycle by cultivating fibre flax in winter. In this system, seeds are sown in autumn, and the crop is harvested in early June. After four consecutive years of monitoring yield and fibre mechanical properties, a selected spring flax variety was grown both in winter 2022/2023 and in spring 2023 for direct comparison. This period included a mild winter favourable for winter crops, and a spring drought that severely impacted spring crops. Plants from the winter crop produced twice as many fibres at mid-stem height as the spring crop, but the mechanical properties of the elementary fibres remained similar in both. However, the elementary fibres in the lower stems of the winter crop averaged only 15 mm in length, compared to 33 mm for the spring crop, which benefited from higher temperatures. Regarding biochemical composition, lignin content in winter flax scutched fibres was significantly higher than in spring flax, at 4.2% versus 2.7%. Cultivating a spring flax variety in winter is thus feasible under favourable conditions, but the resulting fibres are shorter and more lignified, which may pose technical challenges during spinning and could require separating fibres from the lower stems of winter plants to ensure consistent fibre quality. In the final section of the paper, strategies to adapt flax cultivation to climate change are proposed, drawing on the experimental results and current meteorological projections, providing guidance for optimizing crop performance.

Fibers doi: 10.3390/fib14010001

Authors: Qunyi Huang Qingyu Huang Hong Yang Jiahang Zhang Yajie Wu

This paper investigates the fundamental workability of 3D printed concrete materials incorporating different fiber types. Fluidity, extrudability, and buildability were proposed as key indicators for assessing printability, evaluated through corresponding test methods, including fluidity tests, filament extrusion tests, and slump tests. The results demonstrate that the optimal ranges for printability are superplasticizer content between 0.35% and 0.45%, accelerator content between 0.60% and 0.85%, and silica fume replacement level between 7.5% and 10%. The incorporation of copper-coated steel fibers led to deteriorated workability, manifested as reduced fluidity, increased fluidity loss over time, poor pumpability, discontinuous extrusion, and low slump, although buildability remained satisfactory. Polypropylene fibers increased the air content in concrete, thereby improving workability; they exhibited good extrusion continuity, appropriate slump and filament width, and favorable buildability. Basalt fibers significantly enhanced air content and workability. However, due to the high stiffness of the fibers, extrusion continuity was only moderate. While the slump and filament width were suitable, the presence of minor voids in the printed filaments resulted in average buildability.

Fibers doi: 10.3390/fib13120167

Authors: João Marques Madalena Barata Garcia Virgínia Infante Pedro Miguel Amaral Arménio Correia

The building sector faces sustainability issues due to its substantial resource demand, prompting the exploration of alternative materials of natural origin. Given the diverse environmental conditions buildings experience, assessing the impact of these conditions on the mechanical characteristics of alternative materials becomes crucial. This study focuses on a composite comprising stone, agglomerate cork core and glass fiber-reinforced epoxy skins, designed for ventilated facades. The composite underwent an aging cycle commonly applied in the evaluation of construction building materials to evaluate its flexural behavior. To that end, bending tests on unaged and aged samples were carried out to investigate both the bending strength and stiffness. The composite panels were tested in two configurations: (i) stone facing up and (ii) stone facing down. The results indicated that higher bending strength was found in samples where the stone was facing up, regardless of the aging condition. In the stone facing up configuration, the predominant failure mode was stone crushing, whereas the samples in the stone facing down configuration evidenced a failure mechanism of fiber breakage. Despite the observed morphological differences between aged and unaged specimens, no significant difference was found regarding the bending strength and failure modes in both tested configurations. However, a flexural stiffness reduction of at least 21% was found for every aged specimen.

Fibers doi: 10.3390/fib13120166

Authors: Amanda J. Thompson

Demand for clothing is estimated to increase globally by 4.5% per year, and secondhand clothing is often used to fill that demand. A clear understanding of the environmental impact of secondhand items would support transparency around sustainability, which is a rising consumer concern. This study focuses on the characteristics of the fiber fragment material released during the laundering of secondhand, 100% cotton denim clothing, and the implications of secondhand clothing’s contribution of fiber fragments to the environment. The test method used was AATCC TM212-2021, with detergent, conditioned specimens, and filters. The specimens included thirteen pairs of secondhand men’s 100% cotton jeans (SHS) and two pairs of new jeans (CN controls). This study concluded that the amount of fiber fragmentation material shed by SHS was 23.2% of that shed by CN. While this is less than is shed by new clothing, there is still shed material to consider, including dyes and processing chemicals that can contribute to anthropogenic contamination of the environment. The fiber fragment size and frequency were found to have statistically significant differences between SHS (length 370.5 µm, diameter 16.9 µm, 3093 fiber fragments per filter) and CN (320.7 µm, 13.8 µm, and 5962 fiber fragments per filter).

Fibers doi: 10.3390/fib13120165

Authors: Katarina Didulica Ana Baričević Vesna Zalar Serjun

The incorporation of recycled tyre polymer fibres (RTPF) in cementitious composites provides an effective and sustainable approach in tyre waste management while offering potential benefits in mitigating early-age volume deformations. This study evaluates the influence of RTPFs, used in dry (RTPFd) and pre-wetted (RTPFw) states, on key hydration processes governing autogenous shrinkage in cement pastes with w/c of 0.4 and 0.22. The results show that RTPF reduced workability and altered the setting process due to the fibre–matrix mechanical interactions. Incorporation of RTPFs induced changes in water distribution at the fibre surface, delaying self-desiccation and maintaining higher internal relative humidity. While RTPFs offer a beneficial reduction in autogenous shrinkage by 12–41% in mixtures with w/c of 0.4 and by 15–34% in mixtures with w/c of 0.22, RTPFs also increased porosity, which contributed to a reduction in 28-day compressive strength of up to 16%. These findings highlight the dual effect of RTPF on early-age performance and provide insight into their potential application in sustainable cementitious composites.

Fibers doi: 10.3390/fib13120164

Authors: Ramdane Sidali Amrouche Samira Djaknoun Messaoud Saidani Zineb Abeoub Giangiacomo Minak

Despite increased utilization of high-performance mortars in construction, there remains a paucity of research concerning the bond performance of steel reinforcement, particularly within masonry structures. This study characterizes the bond stress behavior in high-performance steel fiber mortar (HPSFRM) to define critical design bond stress parameters. Pull-out tests were performed, incorporating three primary variables: compressive resistance, steel fiber volume, and steel rebars diameter. To support safe and reliable bond design in HPSFRM precast members, various methods for analyzing bond strength, alongside empirical predictive equations, were evaluated. The results revealed that although the rate of increase in bond strength was impacted by the incorporation of steel fibers, the bond strength demonstrated significant improvement in the mortar compressive strength. Introducing steel fibers at a volumetric content of 1% doubled the bond strength. The optimum fiber content was found at 1%, where bond strength increased by 6% and slip by 102% due to effective fiber bridging. Increasing the dosage to 2% yielded only a marginal 2–5% gain, hindered by clustering and poor dispersion. Variations in steel bar diameter had a more pronounced effect on bond stress behavior. The proposed model addresses the underestimation of bond strength and ductility by existing empirical models and code provisions.

Fibers doi: 10.3390/fib13120163

Authors: Maria Modestou Dionisis Semitekolos Tao Liu Christina Podara Savvas Orfanidis Ana Teresa Lima Costas Charitidis

Wind turbine blades (WTBs) have always been considered one of the greatest engineering achievements. They primarily use glass fiber-reinforced polymers (GFRPs) because of their lightweight nature, impressive strength-to-weight ratio, and durability. Until now, typical disposal methods of End-of-Life (EoL) WTBs are landfill or incineration. However, such practices are neither environmentally sustainable nor compliant with current regulations. This study investigates a low-temperature solvolysis process using a poly(ethylene glycol)/NaOH system under ambient pressure for efficient decomposition of the polyester matrix, promoting the potential of chemical recycling as an alternative to landfilling and incineration by offering a viable method for recovering glass fibers from WTB waste. A parametric study evaluated the influence of reaction time (4–5.5 h) and catalyst-to-resin ratio (0.1–2.0 g NaOH per g resin) on solvolysis efficiency. Optimal conditions (200 g PEG200, 12.5 g NaOH, 10 g GFRP, 5.5 h) achieved an ~80% decomposition efficiency and fibers exhibiting minimal surface degradation. SEM and EDX analyses confirmed limited morphological damage, while excessive NaOH (>15 g) caused notable etching of the glass fibers. ICP-OES of liquid residues detected high Na (780 mg/L) and Si (139 mg/L) concentrations, verifying partial dissolution of the fiber structure under strongly alkaline conditions. After applying a commercial sizing agent (Hydrosize HP2-06), TGA confirmed ~1.2% sizing mass, and nanoindentation analysis showed the interfacial modulus and hardness of re-sized fibers improved by over 70% compared to unsized recycled fibers, approaching the performance of virgin fibers.

Fibers doi: 10.3390/fib13120162

Authors: Marta Goliszek-Chabros Omid Hosseinaei

High production costs and sustainability issues are the main factors limiting the widespread application of carbon fibers in various industrial sectors. Lignin, a by-product from the paper and pulping industry, due to its high carbon content of up to 60%, can be considered a potential replacement for polyacrylonitrile in carbon fiber production. The production of lignins with distinct molecular weight distributions as well as group functionalities is essential to enhance high-value applications of lignin. In this study, we present a simple, green solvent-based fractionation method for LignoBoost softwood kraft lignin to obtain a lignin fraction with tailored physicochemical properties for electrospun carbon fiber production without polymeric spinning additives. Sequential solvent extraction was used to produce two fractions with distinct molecular weights: low-molecular-weight softwood kraft lignin (LMW-SKL) and high-molecular-weight softwood kraft lignin (HMW-SKL). The lignin fractions were characterized using size exclusion chromatography (SEC) for the molar mass distribution. The thermal properties of lignins were studied using thermogravimetry (TGA) and differential scanning calorimetry (DSC). Hydroxyl group content was quantified using quantitative 31P NMR spectroscopy. We successfully demonstrated the electrospinning of a high-molecular-weight lignin fraction—obtained in high yield from the fractionation process—without the use of any additives, followed by thermal conversion to produce electrospun carbon fibers. The presented results contribute to the valorization of lignin as well as to the development of green and sustainable technologies.

Fibers doi: 10.3390/fib13120161

Authors: Magaly Granda Ezequiel Zamora-Ledezma Michael Macías Pro Joseph Guamán Alexis Debut Frank Alexis Frederico B. De Sousa Christian Narváez-Muñoz

This study presents the fabrication and performance analysis of multilayer membranes produced by electrospinning using polyacrylonitrile (PAN), chitosan (CS), and Nylon 6 (N6) for the removal of chromium (Cr) and cadmium (Cd) from water. The electrospun membranes were configured in six different multilayer structures. The morphological and mechanical properties of the membranes were evaluated using SEM and tensile testing. Adsorption experiments were performed using synthetic and real water samples from the Cutuchi River. The multilayer membranes demonstrated metal ion removal efficiencies up to 80.81% for Cr6+ and 78.98% for Cd2+ in synthetic water, and similar performance in real samples. These results validate the use of multilayer electrospun membranes as an effective, environmentally friendly method for water purification applications.

Fibers doi: 10.3390/fib13120160

Authors: Said Elkholy Mohamed Salem Ahmed Godat

Numerous experimental and numerical studies have extensively investigated the performance of reinforced deep beams made with natural coarse aggregate concrete. However, limited research has been carried out on reinforced deep beams made of concrete with coarse aggregate from recycled materials and steel fibers. The main goal of this research is to create an accurate finite element model that can mimic the behavior of deep beams using concrete with recycled coarse aggregate and different ratios of steel fibers. The suggested model represents the pre-peak, post-peak, confinement, and concrete-to-steel fiber bond behavior of steel fiber concrete, reinforcing steel, and loading plates by incorporating the proper structural components and constitutive laws. The deep beams’ nonlinear load–deformation behavior is simulated in displacement-controlled settings. In order to verify the model’s correctness, the ultimate loading capacity, load–deflection relationships, and failure mechanisms are compared between numerical predictions and experimental findings. The comparison outcomes of the performance of the beams demonstrate that the numerical model effectively predicts the behavior of deep beams constructed with recycled coarse aggregate concrete. The findings of the experiment and the numerical analysis exhibit a high degree of convergence, affirming the model’s capability to accurately simulate the performance of such beams. In light of how accurately the numerical predictions match the experimental results, an extensive parametric study is conducted to examine the impact of parameters on the performance of deep beams with different ratios of steel fibers, concrete compressive strength, type of steel fibers (short or long), and effective span-to-effective depth ratio. The effect of each parameter is examined relative to its effect on the fracture energy.

Fibers doi: 10.3390/fib13120159

Authors: Lais Alves Tabata Barreto Nordine Leklou Silvio de Barros

The search for sustainable alternatives to synthetic composites has become increasingly relevant in aerospace engineering education and student rocketry. Fiberglass is widely used for rocket fuselages due to its favorable balance of performance and cost, but it is energy-intensive, non-biodegradable, and environmentally burdensome. This study provides the first demonstration of natural fiber composites applied to student rocket fuselages, evaluating bamboo and jute as sustainable alternatives to fiberglass. Fiberglass, bamboo, and jute laminates were fabricated following the procedures of the RocketWolf team at CEFET/RJ. The fuselages were characterized by parachute ejection tests, surface roughness analysis, and flight simulations using OpenRocket software. Additional data such as laminate mass, wall thickness, fiber–resin ratio, and cost analysis were incorporated to provide a comprehensive assessment. Results revealed contrasting behaviors: untreated bamboo composites showed poor resin impregnation, brittle behavior, and lack of structural stability, confirming their unsuitability without chemical treatment. Jute composites, in contrast, achieved adequate impregnation, cylindrical geometry, and superior surface roughness (Ra = 37 µm) compared to fiberglass with paint (62 µm) or envelopes (52 µm). Both fiberglass and jute fuselages successfully passed parachute ejection tests, while simulations indicated apogees close to 1 km, fulfilling competition requirements. The jute fuselage also presented slightly improved stability margins. Economically, jute was ~492% cheaper than fiberglass in fiber-only comparison but absorbed more resin; nevertheless, real purchase prices favored jute. These findings confirm that jute composites are a technically feasible, cost-effective, and sustainable substitute for fiberglass in student rocket fuselages. Beyond technical validation, this work demonstrates the educational and environmental benefits of integrating natural fibers into academic rocketry, bridging sustainability, performance, and innovation.

Fibers doi: 10.3390/fib13120158

Authors: Ilektra Tourkantoni Konstantinos Tserpes Dimitrios Marinis Ergina Farsari Eleftherios Amanatides

The rapid expansion of carbon-fiber-reinforced polymer (CFRP) applications in aerospace, automotive, and energy sectors has intensified concerns over end-of-life waste and the absence of efficient recycling solutions. Plasma-assisted solvolysis has emerged as a promising hybrid approach, combining oxidative chemical treatment with plasma activation to accelerate matrix degradation. In this study, CFRP cylinders (6.4 cm height, 5.5 cm internal, and 6.0 cm external diameter) were processed in a closed-loop plasma solvolysis system under varied operational parameters, including plasma power, plasma gas composition, and nitric acid concentration. The mechanical performance of the recovered carbon fibers was assessed through single-fiber tensile and microbond tests, evaluating both tensile and interfacial properties. In most cases, the recycled fibers retained—or even exceeded—the tensile strength of their virgin counterparts, reaching up to 1.49 times that of the virgin fibers. Young’s modulus, though more variable, ranged from 0.48 to 1.67 times the reference value depending on treatment conditions. Elongation at break generally increased, particularly in the 24K (24,000-filaments) fiber sets, suggesting improved surface ductility. Weibull statistical analysis indicated higher consistency in 3K (3000-filaments) fiber batches compared to 24K, whereas interfacial shear strength was moderately retained across conditions. Overall, balanced plasma and acid conditions enabled efficient fiber recovery with high strength and interfacial performance, validating plasma-assisted solvolysis as a viable route for recovering high-performance fibers suitable for structural reuse, in alignment with circular economy principles.

Fibers doi: 10.3390/fib13120157

Authors: Ioannis Filippos Kyriakidis Anargiros Karelis Nikolaos Kladovasilakis Eleftheria Maria Pechlivani Konstantinos Tsongas

This review paper explores the influence of natural byproducts on polymer matrices via additive manufacturing (AM), focusing specifically on the development of eco-friendly composite materials. A broad range of lignocellulosic residues—such as sawdust, wood chips, bark, and other related byproducts—are evaluated for their potential incorporation into polymer matrices to create filaments and pastes appropriate for AM techniques. The paper initially examines the features of natural byproducts and their typical uses, then evaluates the benefits that AM presents in comparison to conventional manufacturing techniques. Special emphasis is placed on the physicochemical and mechanical properties of the developed composites, encompassing their thermal characteristics (glass transition temperature, melting point, and stability), density, and mechanical behavior under both static and dynamic loading. Furthermore, the environmental effects of these composites are thoroughly assessed through Life Cycle Assessment (LCA), highlighting their contribution to minimizing ecological footprints and promoting circular economy initiatives. Collectively, the findings indicate that the additive manufacturing of composites derived from natural byproducts represent a promising pathway toward sustainable industrial production.

Fibers doi: 10.3390/fib13110156

Authors: Trupti Amit Kinjawadekar Shantharam Patil Gopinatha Nayak

Corrosion continues to be a major challenge affecting the service life, safety and durability of steel-reinforced concrete (RC) structures. The deterioration of steel not only reduces structural capacity but also increases long-term maintenance costs. To address this limitation, glass fiber-reinforced polymer (GFRP) is being investigated as an alternative to conventional steel reinforcement, particularly in aggressive environments. This work examines the behavior of composite columns reinforced with GFRP bars with steel stirrups. Sixteen square columns of 150 × 150 × 850 mm dimensions, cast with M30 grade concrete, were reinforced using either GFRP or steel, while varying stirrup spacing and bar diameters. Experimental observations showed that GFRP reinforcement contributed about 10–12% of the ultimate capacity of the columns. A marked enhancement in load carrying capacity of GFRP-RC columns was obtained with closer stirrup spacing. The axial strength of GFRP-reinforced columns was comparable to steel-reinforced ones with the same main reinforcement ratio. Ductility increased by 12% when stirrup spacing was reduced. The difference between analytical and experimental values ranged between 12% and 15%, whereas experimental and numerical results differed by 10–12%. Based on these results, a modification factor derived from IS 456:2000 is proposed for predicting the capacity of ‘GFRP-reinforced’ columns. The outcomes clearly highlight the potential of GFRP reinforcement as a durable, sustainable and practical substitute for conventional steel reinforcement.