Fibers

18 pages, 2431 KB

Open AccessArticle

Experimental Study of the Aging Effect on the Mechanical Properties of Hemp Fiber Cementitious Composite

by Miquel Ángel Chamorro, Jaume Font, Irieix Costa, Jordi Soler and Joan Llorens

Fibers 2026, 14(7), 87; https://doi.org/10.3390/fib14070087 - 17 Jul 2026

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) [...] Read more.

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. Full article

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27 pages, 2854 KB

Open AccessArticle

Drying Process Development for Lignocellulosic Water Hyacinth Fibers: Design and Performance Evaluation of an Innovative Dryer Machine for Small-Scale Craft Industry

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

Fibers 2026, 14(7), 86; https://doi.org/10.3390/fib14070086 - 17 Jul 2026

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Research on Wood and Lignocellulosic Materials)

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17 pages, 9287 KB

Open AccessArticle

An Efficient Method for Recycling Polypropylene with the Antioxidant Additive Propyl Gallate

by Rinat Iskakov, Gulbarshin Shambilova, Zhanar Kadasheva, Danagul Kalimanova, Meirbek Naukenov, Alexander Korshunov, Igor Makarov, Markel Vinogradov and Georgy Makarov

Fibers 2026, 14(7), 85; https://doi.org/10.3390/fib14070085 - 17 Jul 2026

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Fiber-Reinforced Concrete Under Environmental, Mechanical, and Thermal Actions)

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36 pages, 4347 KB

Open AccessArticle

Feed-Controlled Filament Extrusion of High-Loading Micronized Soy Hull Fiber/PLA Biocomposites for Fused Deposition Modeling

by Muneeb Tahir, Tri Vu and Abdel-Fattah M. Seyam

Fibers 2026, 14(7), 84; https://doi.org/10.3390/fib14070084 - 16 Jul 2026

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Fibers and Fiber-Reinforced Composite: Processing-Structure-Property Relationships)

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Graphical abstract

47 pages, 5846 KB

Open AccessReview

A Concise Review of Carbon Fibers Focused on Polyethylene as Precursor: From Discovery to Origin of Mechanical Properties and Application Potential

by Jochen Straetmans and Mario Smet

Fibers 2026, 14(7), 83; https://doi.org/10.3390/fib14070083 - 15 Jul 2026

Abstract

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 [...] Read more.

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. Full article

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28 pages, 10207 KB

Open AccessArticle

Parametric Influence of Yarn Microstructure on Coupled Heat and Moisture Transport

by Wang Xu, Yunchu Yang and Abdel-Fattah Seyam

Fibers 2026, 14(7), 82; https://doi.org/10.3390/fib14070082 - 15 Jul 2026

Abstract

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 [...] Read more.

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. Full article

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Graphical abstract

25 pages, 4460 KB

Open AccessFeature PaperArticle

Study on Dry Shrinkage Cracking and Shear Strength of Expansive Soils Synergistically Improved with Biochar and Sisal Fibers

by Long Ling, Aijun Chen, Yifan Zhou and Yanping Liu

Fibers 2026, 14(7), 81; https://doi.org/10.3390/fib14070081 - 13 Jul 2026

Abstract

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 [...] Read more.

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. Full article

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19 pages, 2864 KB

Open AccessArticle

Intra and Inter-Specimen Strain Heterogeneity in Filament–Wound Carbon Fiber Composites Revealed by Digital Image Correlation

by Javier Pisonero, Enrique González-González, Manuel Rodríguez-Martín and Roberto García-Martín

Fibers 2026, 14(7), 80; https://doi.org/10.3390/fib14070080 - 3 Jul 2026

Abstract

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) [...] Read more.

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. Full article

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19 pages, 1400 KB

Open AccessReview

Steam Explosion Processing of Bast Fibers: Effects on Fiber Structure and Performance in Textile and Composites Applications

by Peter El Hage, Roland El Hage, César Segovia, Jingjing Liao, Didilia Ileana Mendoza-Castillo, Nicolas Brosse and Henri Vahabi

Fibers 2026, 14(7), 79; https://doi.org/10.3390/fib14070079 - 2 Jul 2026

Abstract

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, [...] Read more.

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. Full article

(This article belongs to the Special Issue Advances in Bast Fiber Processing into Yarns: Characterization, Performance and Sustainable Textile Applications)

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23 pages, 7259 KB

Open AccessArticle

Influence of Local Fiber Orientation Deviations on the Dynamic and Mechanical Response of CFRP Laminates for UAV Structures

by Maciej Milewski

Fibers 2026, 14(7), 78; https://doi.org/10.3390/fib14070078 - 2 Jul 2026

Abstract

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 [...] Read more.

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. Full article

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22 pages, 1328 KB

Open AccessArticle

Dynamic Parameters of Fiber-Reinforced Soils at Very Small Strains

by Konstantinos E. Bantralexis, Eleni S. Boura, Ioannis N. Markou and Evangelos D. Evangelou

Fibers 2026, 14(7), 77; https://doi.org/10.3390/fib14070077 - 29 Jun 2026

Abstract

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 [...] Read more.

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 (V_s), the velocity of the primary wave (V_p), 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. Full article

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25 pages, 3354 KB

Open AccessArticle

Damage Monitoring in Recycled Aggregate Concrete Reinforced with Hybrid Steel–Polyolefin Fibers Using Acoustic Emission Technique

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

Fibers 2026, 14(6), 76; https://doi.org/10.3390/fib14060076 - 21 Jun 2026

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Recent Developments in Structural Applications of Fiber-Reinforced Concrete)

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16 pages, 3035 KB

Open AccessArticle

Experimental and Numerical Analysis of Electrospun Polylactic Acid Fiber Deposition: Effects of Processing Parameters on Morphology and Coating Uniformity

by Savaş Evran, Nazmi Ekren, Merve Yılmaz, Ali Samet Sarkın, L. Duta and Oğuzhan Gündüz

Fibers 2026, 14(6), 75; https://doi.org/10.3390/fib14060075 - 18 Jun 2026

Abstract

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 [...] Read more.

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. Full article

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25 pages, 17296 KB

Open AccessArticle

A Study on the Long-Term Performance Evaluation of Carbon-Fiber Reinforced Polymer (CFRP) Tendon

by Jongeok Lee, Sung-Jin Lee and Woo-Tai Jung

Fibers 2026, 14(6), 74; https://doi.org/10.3390/fib14060074 - 17 Jun 2026

Abstract

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 [...] Read more.

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. Full article

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19 pages, 3475 KB

Open AccessArticle

Multidirectional Surface Roughness Characterization of Woven Fabrics for Hospital Applications

by Ana Kalazić, Ana Palčić, Snježana Brnada and Sandra Flinčec Grgac

Fibers 2026, 14(6), 73; https://doi.org/10.3390/fib14060073 - 12 Jun 2026

Abstract

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 [...] Read more.

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. Full article

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19 pages, 22617 KB

Open AccessArticle

Experimental Evaluation of the Flexural and Bearing Mechanical Properties of Dragonwood in Jacking Applications in Comparison to Ekki

by Herry Chen, Tolulope Alayande, Mateya Hughes, Maxime Daviau, Catherine Shrimpton, Tyler Hull and Daniel Lacroix

Fibers 2026, 14(6), 72; https://doi.org/10.3390/fib14060072 - 12 Jun 2026

Abstract

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 [...] Read more.

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. Full article

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10 pages, 3898 KB

Open AccessArticle

Influence of Water Storage on the Mechanical Properties of Short Fiber-Reinforced Dental Resin Composites

by Yoshiki Ishida, Daisuke Miura, Yasuhiro Hotta and Akikazu Shinya

Fibers 2026, 14(6), 71; https://doi.org/10.3390/fib14060071 - 11 Jun 2026

Abstract

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 [...] Read more.

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. Full article

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25 pages, 4352 KB

Open AccessArticle

Green Chemistry in Hemp Dyeing

by Vasilica Popescu, Marina Marin, Gabriel Popescu, Viorica Vasilache and Andrei Popescu

Fibers 2026, 14(6), 70; https://doi.org/10.3390/fib14060070 - 9 Jun 2026

Abstract

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 [...] Read more.

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. Full article

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56 pages, 7632 KB

Open AccessReview

Research Progress on Advanced Molding Technologies for Carbon Fiber-Reinforced Polymer Composites: Defect Control and Process Optimization

by Qun Li, Xufeng Song, Longzhan Zheng, Guangxi Li, Qingqing Lü, Liquan Yang, Erbo Liu, Yuqin Ma and Zhoukui Li

Fibers 2026, 14(6), 69; https://doi.org/10.3390/fib14060069 - 8 Jun 2026

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Topic Advanced Composites Manufacturing and Plastics Processing, 2nd Volume)

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