Search Results (37)

Woven composites and natural fiber-reinforced composites both have widespread applications in various industries due to their appealing load-carrying capacity and performance compared to conventionally manufactured composites, such as polymeric composites. Representative volume element (RVE) generation is one of the most effective and widely adopted methods for estimating mechanical performance in current research. This study aims to explore the effects of three significant factors in woven composite RVEs: yarn spacing (from 0.5 mm to 1.5 mm), fabric thickness (from 0.2 to 0.5 mm), and shear angle (from 3.5 to 15 degrees) through finite element methods and statistical analysis to understand their effectiveness in the elastic moduli’s. The validation of this research has been conducted using available literature. The generation of representative volume elements (RVEs) and the calculation of elastic moduli were performed using ANSYS-19, including the material designer feature. The experimental design was carried out using Design-Expert software version 13, which used response surface methodology. The materials selected for this study were jute fiber and epoxy. After obtaining the elastic moduli from the ANSYS material designer, three responses were considered: longitudinal Young’s modulus (E₁₁), in-plane shear modulus (G₁₂), and major Poisson’s ratio (V₁₂). ANOVA (Analysis of Variance) and 3D contour graphs were generated to further analyze and correlate the effects of the selected materials on these responses. These investigations revealed that in comparison to twill structure, plain structure in natural fiber-reinforced woven composites could be a good alternative. Additionally, the findings highlighted that yarn spacing and fabric thickness significantly influence the considered moduli in plain-weave NFRC material RVEs. However, in twill-woven composite RVEs, the effects of yarn spacing, fabric thickness, and shear angle were found to be considerable. Moreover, statistical analysis has found the best combinations for both plain and twill structures, while the yarn spacing was 1 mm, the shear angle was 9.25 degrees, and the fabric thickness was 0.35 mm. Full article

The aim of this series of tests was to characterize the alkali and water resistance of alkali-resistant (durability) glass filaments, which were optimized with two non-vulcanized formulations based on co-polymerizing styrene-butadiene rubbers (CemFil-SBR1 and CemFil-SBR2). Furthermore, it was assessed which of the two polymer-impregnated multifilament yarns is the better alternative for use in cementitious binders. For this purpose, the impregnated multifilament yarns were chemically conditioned for up to twelve months at temperatures of 23 and 50 °C in 2.5 percent sodium hydroxide solution and 2.5 percent potassium hydroxide solution as well as in 3 percent salt and distilled water. The samples were then subjected to material science tests. The liquid absorption capacities and the changes in the mass of the composite materials were determined at different times during conditioning. The load-bearing capacity of the samples was also tested using uniaxial fiber strand tensile tests. The durability of the polymer-impregnated multifilament yarns was described in detail in conjunction with scanning electron microscopy images and nominal cross-section determinations. The test liquids caused a reduction in strength during the storage period, which was accelerated by increased temperatures. The reduction in strength is mainly due to glass corrosion of the filaments. Glass corrosion is delayed due to the good impregnation quality, which fundamentally improves the durability of the yarns. The results of the durability tests show that the polymer-impregnated multifilament yarns CemFil-SBR2 are probably more suitable for use in cementitious binders, as they have better alkali and hydrolysis resistance. Full article

This work aims to describe and predict the complex mechanical behavior of polymeric cords used as reinforcements in tires. Starting from the observed microstructure of the cords and from macroscopic experimental tests performed on single-ply yarns, a comprehensive geometric and mechanical model is developed. The real geometry of the cord is replaced by an equivalent three-dimensional continuum of a cylindrical shape, with a properly defined non-isotropic inelastic constitutive behavior. The three-dimensional viscoelastic and viscoplastic material model developed by the authors for rayon fibers is employed for this purpose. The actual directions of filaments inside the cord are computed by an analytical model, accounting for the twist in the yarns and in the filaments inside each yarn. Such directions, relevant to points of the cord cross-section, are then averaged along the pitch of the cord to obtain mean directions which represent the virtual reinforcement directions to be used in the equivalent cylindrical-shaped model. This analysis strategy is implemented in a finite element procedure. For rayon cords, the developed simulation tool (fed with appropriate parameters) gives numerical results that compare well with the corresponding experimental results. This approach could be effectively utilized in the analysis of cord-reinforced rubber composites. Full article

The annual demand for fibres continues to rise worldwide. Consequently, more and more fibres must be produced to meet this demand, most of which are melt-spun polymeric man-made fibres. Smooth filaments made of polymers are mainly used for technical applications in industry. For use in clothing or home textiles, for example, a texturing process is used to give the filaments a crimp and thus a feel like that of natural fibres. In this state, they can be processed together with natural fibres and used in textiles. Partially oriented yarns (POY) are of great importance in texturing. The yarns are mainly crimped with the help of the so-called false-twist texturing process (FTTP). Since POY accounts for about 60% of the melt-spun filament yarn produced worldwide, the FTTP is the most important texturing process in the textile industry. In this paper, the main components of false-twist texturing (FTT) machines are explained, along with the state of the art and research for each component and its influence on the process. Relevant patents are discussed, as well as process optimisation techniques, innovative polymers, and yarn types recently used in FTT, followed by a conclusion and an outlook for the process. Full article

The inclusion of particles in a polymeric substrate to achieve certain properties is a well-known practice. In the case of textile substrates, this practice may deeply affect the structure of the produced yarns, as even a filament with no textile applications can be obtained. In this manuscript, titanium dioxide (TiO₂) particles were incorporated into polyester (PET) chips and the influence of these fillers on the properties of yarn and fabric, and the ultraviolet protection factor (UPF) was assessed. For this purpose, rutile and anatase crystalline forms of TiO₂, as well as the size of the particles, were evaluated. Moreover, parameters such as mechanical properties, orientation of the macromolecules and thermal behavior were analyzed to ensure that the textile grade is maintained throughout the production process. The results showed that the inclusion of micro- and nanoparticles of TiO₂ decreases the molecular weight and tenacity of PET. Also, although orientation and crystallinity varied during the textile process, the resulting heatset fabrics did not present important differences in those parameters. Finally, the attainment of textile-grade PET-TiO₂ fabrics with UPF indexes of 50+ with both rutile and anatase and micro- and nano-sized TiO₂ forms was demonstrated. Full article

Textile-based sensors fabricated using the direct-coating method are the appropriate choice to meet the aspects of flexibility, non-invasiveness, and lightness for continuous monitoring of the human body. The characteristics of the sensor substrate are directly influenced by factors such as the type of weave, thread fineness, fabric density, and the type of polymeric constituent fibers. The fabric used as the sensor substrate, fabricated using the direct-coating method, must be capable of retaining the electrode paste solution, which has higher viscosity, on one surface of the fabric to avoid short circuits during the fabrication process. However, during its application, this fabric should allow the easy passage of analyte solutions with low viscosity as much as possible. Hence, an appropriate fabric construction is required to serve as the substrate for textile-based sensors to ensure the success of the fabrication process and the effectiveness of the resulting sensor’s performance. The development of the structural design of the fabric to be used as a substrate for non-invasive biosensors with a multilayer concept is carried out by weaving and sewing processes utilizing polyester-viscose fibers. During the production process, variations are applied, such as weft yarn density, the characterization of wetting time, absorption rate, maximum wetted radius, spreading speed, and accumulative one-way transport index. The most suitable fabric for use as a substrate for non-invasive biosensors with a multilayer concept, such as in this research, is a fabric with a weft thread density of 70 strands per inch, along with the addition of an analyte transfer thread configuration. Full article

An imperative requisite of tissue-engineered scaffolds is to promote host cell regeneration and concomitantly thwart microbial growth. Antibacterial agents are often added to prevent implant-related infections, which, however, aggravates the risk of bacterial resistance. For the first time, we report a fiber-based platform that selectively promotes the growth of mammalian cells and alleviates bacteria by varying fiber size, orientation, and material of polymeric yarns. The interactions of Gram-positive and -negative bacterial species with mammalian mesenchymal stem cells (MSC) were investigated on poly-€-caprolactone (PCL) yarns, polyethylene terephthalate (PET), poly-L-lactic acid (PLLA), and cotton. Various yarn configurations were studied by altering the fiber diameter (from nano- to microscale) and fiber orientations (aligned, twisted, and random) of PCL yarns. PCL nanofibrous yarn decreased the adhesion of S. aureus and E. coli, with a 2.7-fold and 1.5-fold reduction, respectively, compared to PCL microfibrous yarn. Among different fiber orientations, nanoaligned fibers resulted in an 8-fold and 30-fold reduction of S. aureus and E. coli adhesion compared to random fibers. Moreover, aligned orientation was superior in retarding the S. aureus adhesion by 14-fold compared to nanotwisted fibers. Our data demonstrate that polymeric yarns comprising fibers with nanoscale features and aligned orientation promote mammalian cell adhesion and spreading and concomitantly mitigate bacterial interaction. Moreover, we unveil the wicking of cells through polymeric yarns, facilitating early cell adhesion in fibrous scaffolds. Overall, this study provides insight to engineer scaffolds that couple superior interaction of mammalian cells with high-strength fibrous yarns for regenerative applications devoid of antibacterial agents or other surface modification strategies. Full article

The skin is the largest organ and one of the most important in the human body, and is constantly exposed to pathogenic microorganisms that cause infections; then, pharmacological administration is required. One of the basic medical methods for treating chronic wounds is to use topical dressings with characteristics that promote wound healing. Fiber-based dressings mimic the local dermal extracellular matrix (ECM), maintaining an ideal wound-healing climate. This work proposes electrospun PHB/PEG polymeric microfibers as dressings for administering the antibiotic gentamicin directed at skin infections. PHB-PEG/gentamicin fibers were characterized before and after plasma treatment by Raman spectroscopy, FTIR, and XRD. SEM was used to evaluate fiber morphology and yarn size. The plasma treatment improved the hydrophilicity of the PHB/PEG/gentamicin fibers. The release of gentamicin in the plasma-treated fibers was more sustained over time than in the untreated ones. Full article

The hierarchical structure and microscale dimensions of carbon nanotube yarns (CNTYs) make them great candidates for the development of integrated sensing applications. The change in the electrical resistance of CNTYs due to mechanical strain, known as piezoresistivity, is the principal mechanism in strain sensing using CNTYs. While the axial tensile properties of CNTYs have been studied widely, studies on the axial piezoresistive response of CNTYS under compression have been limited due to the complexities associated with the nature of the experiments involving subjecting a slender fiber to compression loading in its axial direction. In this study, the piezoresistive response of a single CNTY embedded into a polymeric resin (CNTY monofilament composite) was investigated under axial compression. The results suggest that the CNTY exhibits a strong piezoresistive response in the axial direction with sensitivity or gauge factor values in the order of 0.4–0.5 for CNTY monofilament composites. The piezoresistive response of the CNTY monofilament composites under compression was compared to that under tension and it was observed that the sensitivity appears to be slightly lower under compression. The potential change in sensitivity between the freestanding CNTY and the CNTY monofilament composite under compression is still unknown. Knowing the axial piezoresistive response of the CNTYs under both tension and compression will enable their use in sensing applications where the yarn undergoes compression including those in aerospace and marine structures, and civil or energy infrastructure. Full article

In this work, a novel wire-shaped supercapacitor based on nylon yarn with a high specific capacitance and energy density was developed by designing an asymmetric configuration and integrating pseudocapacitive materials for both electrodes. The nylon/Ag/MnO₂ yarn was prepared as a positive electrode by electrochemically depositing MnO₂ on a silver-paste-coated nylon yarn. Additionally, PPy was prepared on nylon/Ag yarn by chemical polymerization firstly to enlarge the surface roughness of nylon/Ag, and then the PPy could be easily coated on the chemically polymerized nylon/Ag/PPy by electrochemical polymerization to obtain a nylon/Ag/PPy yarn-shaped negative electrode. The wire-shaped asymmetric supercapacitor (WASC) was fabricated by assembling the nylon/Ag/MnO₂ electrode, nylon/Ag/PPy electrode and PAANa/Na₂SO₄ gel electrolyte. This WASC showed a wide potential window of 1.6 V and a high energy density varying from 13.9 to 4.2 μWh cm⁻² with the corresponding power density changing from 290 to 2902 μW cm⁻². Meanwhile, because of the high flexibility of the nylon substrate and superior adhesion of active materials, the WASC showed a good electrochemical performance stability under different bending conditions, suggesting its good flexibility. The promising performance of this novel WASC is of great potential for wearable/portable devices in the future. Full article

The accelerated aging of polyethylene terephthalate (PET) multifilament yarns containing nano or microparticles of titanium dioxide (TiO₂), silicon carbide (SiC), or fluorite (CaF₂) at a maximum percentage of 2% has been studied. For this, the yarn samples were introduced into a climatic chamber at 50 °C, 50% relative humidity, and an ultraviolet A (UVA) irradiance of 1.4 W/m². They were then removed from the chamber after periods of between 21 and 170 days of exposure. Subsequently, the variation in weight average molecular weight, number molecular weight, and polydispersity was evaluated by gel permeation chromatography (GPC), the surface appearance was evaluated using scanning electron microscopy (SEM), the thermal properties were evaluated using differential scanning calorimetry (DSC), and the mechanical properties were evaluated using dynamometry. The results showed that, at the test conditions, there was degradation in all of the exposed substrates, possibly due to the excision of the chains that make up the polymeric matrix, which resulted in the variation in the mechanical and thermal properties depending on the type and size of the particle used. This study provides insight into the evolution of the properties of PET-based nano- and microcomposites and might be helpful when selecting materials for specific applications, which is of great interest from an industrial point of view. Full article

Succinylcholine (SUX) is a clinical anesthetic that induces temporary paralysis and is degraded by endogenous enzymes within the body. In high doses and without respiratory support, it results in rapid and untraceable death by asphyxiation. A potentiometric thread-based method was developed for the in-field and rapid detection of SUX for forensic use. We fabricated the first solid-contact SUX ion-selective electrodes from cotton yarn, a carbon black ink, and a polymeric ion-selective membrane. The electrodes could selectively measure SUX in a linear range of 1 mM to 4.3 $\mathsf{\mu }$M in urine, with a Nernstian slope of 27.6 mV/decade. Our compact and portable yarn-based SUX sensors achieved 94.1% recovery at low concentrations, demonstrating feasibility in real-world applications. While other challenges remain, the development of a thread-based ion-selective electrode for SUX detection shows that it is possible to detect this poison in urine and paves the way for other low-cost, rapid forensic diagnostic devices. Full article

Stretchable yarn/fiber electronics with conductive features are optimal components for different wearable devices. This paper presents the construction of coil structure-based carbon nanotube (CNT)/polymer fibers with adjustable piezoresistivity. The composite unit fiber is prepared by wrapping a conductive carbon CNT sheath onto an elastic spandex core. Owing to the helical coil structure, the resultant CNT/polymer composite fibers are highly stretchable (up to approximately 300%) without a noticeable electrical breakdown. More specifically, based on the difference in the coil index (which is the ratio of the coil diameter to the diameter of the fiber within the coil) according to the polymeric core fiber (spandex or nylon), the composite fiber can be used for two different applications (i.e., as strain sensors or supercapacitors), which are presented in this paper. The coiled CNT/spandex composite fiber sensor responds sensitively to tensile strain. The coiled CNT/nylon composite fiber can be employed as an elastic supercapacitor with excellent capacitance retention at 300% strain. Full article

This paper presents the evaluation of some electrodes based on polymeric conductive membranes (polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA) and polyethylene glycol (PEG)) for sensor applications. The electrodes were developed using textile support (weave structure-based 100% cotton yarns) and applying conductive membrane layers deposited on the textile surface. Coating the fabrics with thin layers of conductive membranes could generate new surfaces with the electrical resistance specific to conductive samples. Laboratory tests evaluated the physicomechanical and electrical properties. The surface resistance was investigated using a digital surface resistance meter by neglecting electrode polarization impedance. In addition, the correlation coefficients between the physicomechanical and electrical parameters obtained by the laboratory were analyzed. These conductive samples can be used to and develop flexible electrodes for moisture, temperature and strain sensors. Full article

Basalt fibre epoxy composites well suit various engineering applications for their mechanical properties and chemical stability. However, after basalt/epoxy product lifespan, there are not many established ways to treat and recycle the fibers without deteriorating their physical, mechanical and chemical properties. In this study, a chemical recycling method for basalt fiber reinforced polymers is presented. The process is based on previous studies concerning carbon fibers epoxy composites in which the fibers are separated from the polymeric matrix through a solvolysis reaction at temperature below 160 °C. Firstly, the specimens are thermally pre-treated in a heater set over the glass transition temperature, to promote the polymeric swelling of the matrix. The chemical degradation is obtained by means of a solution of glacial acetic acid (AcOH) and hydrogen peroxide (H₂O₂): compact, clean, resin-free, recycled woven fabrics are obtained and the original length of the yarns is maintained. Breaking tenacity of the recycled basalt fibers is kept up to 90.5% compared to the virgin ones, while, with a pyrolysis treatment, this value cannot exceed the 35%. Full article