Search Results (107)

Automated fiber placement (AFP) composites exhibit complex mechanical behaviors due to manufacturing-induced mesostructural variations, including resin-rich regions and tow gaps that significantly influence both local stress distributions and global material responses. This study presents a hierarchically nested modeling framework based on the Parametric High-Fidelity Generalized Method of Cells (PHFGMC) to predict the effective elastic properties and nonlinear mechanical response of AFP composites. The PHFGMC model integrates micro- and meso-scale analyses using representative volume elements (RVEs) derived from micrographs of AFP composite laminates to capture these manufacturing-induced characteristics. Multiple RVE configurations with varied gap patterns are analyzed to quantify the influence of mesostructural features on global stress–strain response. Predictions for linear and nonlinear elastic behaviors are validated against experimental results from carbon fiber/epoxy AFP specimens, demonstrating good quantitative agreement with measured responses. A cohesive extension of the PHFGMC framework further captures damage initiation and crack propagation under transverse tensile loading, revealing failure mechanisms specifically associated with tow gaps and resin-rich areas. By systematically accounting for manufacturing-induced variability through detailed RVE modeling, the nested PHFGMC framework enables the accurate prediction of global mechanical performance and localized behavior, providing a robust computational tool for optimizing AFP composite design in aerospace and other high-performance applications. Full article

In recent times, fiber reinforced polymer composite materials have become more popular due to their remarkable features such as high specific strength, high stiffness and durability. Particularly, Carbon Fiber Reinforced Polymer (CFRP) composites are one of the most prominent materials used in the field of transportation and building engineering, replacing conventional materials due to their attractive properties as mentioned. In this work, a CFRP laminate is fabricated with carbon fiber mats and epoxy by a hand layup technique. Alumina (Al₂O₃) micro particles are used as a filler material, mixed with epoxy at different weight fractions of 0% to 4% during the fabrication of CFRP laminates. The important objective of the study is to investigate the influence of alumina micro particles on the mechanical performance of the laminates through characterization for various physical and mechanical properties. It is revealed from the results of study that the mass density of the laminates steadily increased with the quantity of alumina micro particles added and subsequently, the porosity of the laminates is reduced significantly. The SEM micrograph confirmed the constituents of the laminate and uniform distribution of Al₂O₃ micro particles with no significant agglomeration. The hardness of the CFRP laminates increased significantly for about 60% with an increase in weight % of Al₂O₃ from 0% to 4%, whereas the water gain % gradually drops from 0 to 2%, after which a substantial rise is observed for 3 to 4%. The improved interlocking due to the addition of filler material reduced the voids in the interfaces and thereby resist the absorption of water and in turn reduced the plasticity of the resin too. Tensile, flexural and inter-laminar shear strengths of the CFRP laminate were improved appreciably with the addition of alumina particles through extended grain boundary and enhanced interfacial bonding between the fibers, epoxy and alumina particles, except at 1 and 3 wt.% of Al₂O₃, which may be due to the pooling of alumina particles within the matrix. Inclusion of hard alumina particles resulted in a significant drop in impact strength due to appreciable reduction in softness of the core region of the laminates. Full article

Polyaryletherketone (PAEK) polymers inherently exhibit low surface activity, leading to poor adhesive bonding performance when using epoxy-based adhesives. In this study, low-temperature plasma surface modification was conducted on carbon fiber-reinforced polyetherketone ketone (CF/PEKK) composites to investigate the influence of plasma treatment parameters on their lap shear strength. Surface characterization was systematically performed using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and contact angle analysis to evaluate morphological, chemical, and wettability changes induced via plasma treatment. The results demonstrated a significant enhancement in lap shear strength after plasma treatment. Optimal bonding performance was achieved at a treatment speed of 10 mm/s and a nozzle-to-substrate distance of 5 mm, yielding a maximum shear strength of 28.28 MPa, a 238% improvement compared to the untreated control. Notably, the failure mode transitioned from interfacial fracture in the untreated sample to a mixed-mode failure dominated by cohesive failure of the adhesive and substrate. Plasma treatment substantially reduced the contact angle of CF/PEKK, indicating improved surface wettability. SEM micrographs revealed an increased micro-porous texture on the treated surface, which enhanced mechanical interlocking between the composite and adhesive. XPS analysis confirmed compositional alterations, specifically elevated oxygen-containing functional groups on the plasma-treated surface. These modifications facilitated stronger chemical bonding between CF/PEKK and the epoxy resin, thereby validating the efficacy of plasma treatment in optimizing surface chemical activity and adhesion performance. Full article

The study examined composites composed of curauá fibers (10%) and a high-density bio-based polyethylene (HDBPE) matrix, emphasizing the effects of processing methods on their final properties. In addition, plant-derived oils were applied as compatibilizers to improve the interfacial adhesion between the hydrophilic fibers and the hydrophobic HDBPE, thereby supporting the process’s sustainability. The comparative analysis of HDBPE/curauá fiber/plant-based oil composites utilized distinct methodologies: compounding with an internal mixer, followed by thermopressing and mixture composition using a twin-screw extruder with subsequent injection molding. Castor oil (CO), canola oil (CA), or epoxidized soybean oil (OSE) were employed as compatibilizers (5%). All composites displayed high levels of crystallinity (up to 86%) compared to neat HDBPE (67%), likely due to interactions with curauá fibers and compatibilizers. The use of twin-screw extruder/injection molding produced composites with higher impact and flexural strength/modulus-assessed at 5%(approximately 222 J/m to 290 J/m; 22/700 MPa to 26/880 MPa, respectively), considerably exceeding those formed via internal mixer/thermopressing (approximately 110 J/m to 123 J/m; 14/600 MPa to 20/700 MPa). Micrographs of the composites indicated that the extruder separated the fiber bundles into smaller-diameter units, which may have facilitated the transfer of load from the matrix to the fibers, optimizing the composite’s mechanical performance. As a compatibilizer, CO enhanced both properties and, when combined with the twin-screw extruder/injection technique, emerged as the optimal choice for HDBPE/curauá fiber composites. Full article

The viability of using Juncus acutus fibers as reinforcement material for developing lightweight sustainable non-structural construction materials in compliance with the valorization of local by-products has been investigated in this work. This study aims to investigate the effect of the chemical treatment of Juncus acutus fibers on the mechanical and hygric properties of bio-sourced clay–sand–Juncus acutus fiber composite. This lightweight specimen has been produced from a mixture of 60% natural clay and 40% sand by mass, as a matrix, and reinforced with different amounts of Juncus fibers. The fibers were used as a partial replacement of sand in the mixture by volume at 0% (control specimen), 5%, 10%, and 20%. In order to enhance interfacial bonding between the fibers and the binder matrix, which seriously limits the strength development of the composite, the fibers have undergone an NaOH alkali treatment with different concentrations of 1 and 2 wt. %. Morphological and elementary chemical component evaluations based on SEM micrographs and EDX analyses revealed that the 1 wt. % NaOH alkali treatment exhibited the most beneficial effect due to the removal of impurity deposits without significant surface damage to the fibers. This finding was highlighted through the tensile tests carried out which showed the tensile stress value of 81.97 MPa compared to those of the treated fibers with 2% NaOH (74.45 MPa) and the untreated fibers (70.24 MPa). However, mechanical test results, carried out according to the European Standard EN 196-1, highlighted the beneficial effect of the fiber alkali treatment on both the compressive and flexural strengths, particularly for the fiber contents of 5% and 10%, which corresponds to a strengthening rate of 25% and 30%, respectively. The examination of the hygroscopic properties of the samples, including capillary water absorption, water diffusivity, and moisture buffering capacity under the dynamic conditions have indicated that the specimen containing treated fibers exhibited a better moisture regulating property than that obtained with untreated fibers. However, the specimens with treated fibers are classified as excellent hygric regulators based on their moisture buffer values (MBV > 2 g/(m².%RH)), according to the NORDTEST classification. The results also indicated that the capillary water absorption and the apparent moisture diffusivity of composites were lowered due to high fiber-matrix interfacial bond after fiber treatment. Consequently, the composite with treated fibers is less diffusive compared to that with untreated fibers, and thus expected to be more durable in a humid environment. Full article

The increasing application of fiber-reinforced polymer (FRP) composites necessitates the development of composite structures that exhibit high stiffness, high strength, and favorable failure behavior to endure complex loading scenarios and improve damage tolerance. Achieving these properties can be facilitated by integrating conventional FRPCs with metallic materials, which offer high ductility and superior energy absorption capabilities. However, there is a lack of effective solutions for the micro-level hybridization of high-performance filament yarns, metal filament yarns, and thermoplastic filament yarns. This study aims to investigate the hybridization of multi-material components at the micro-level using the air-texturing process. The focus is on investigating the morphological and the mechanical properties as well as the damage behavior in relation to the process parameters of the air-texturing process. The process-induced property changes were evaluated throughout the entire process, starting from the individual components, through the hybridization process, and up to the tape production. Tensile tests on multifilament yarns and tape revealed that the strength of the hybrid materials is significantly reduced due to the hybridization process inducing fiber damage. Morphological analyses using 3D scans and micrographs demonstrated that the degree of hybridization is enhanced due to the application of air pressure during the hybridization process. However, this phenomenon is also influenced by the flow movement of the PP matrix during the consolidation stage. The hybrid laminates exhibited a damage behavior that differs from the established behavior of layer-separated metal fiber hybrids, thereby supporting other failure and energy absorption mechanisms, such as fiber pull-out. Full article

Thermoplastic composites have become increasingly popular due to their numerous benefits. To enhance the performance of fiber-reinforced thermoplastic composites, many research efforts have been made using various types of fillers. However, the high melting temperature and viscosity of thermoplastic polymer melt present a primary challenge in achieving uniform filler dispersion. Interply strengthening is one of the simplest and most cost-effective techniques for addressing this challenge. This study utilized micro-size core-shell particles that were dispersed using a sieve. The particles were carefully sprinkled onto the sieve, facilitating their controlled dispersion at the ply interface, after which fabric and thermoplastic films were laid on top. The resulting stacked arrangement was then processed using a hot consolidation cycle via compression molding to produce composite laminate. The impact of incorporating core-shell particles on the mechanical performance of carbon fiber-reinforced polyamide 6 (CF/PA6) laminates was investigated. Results showed that adding 4 wt% core-shell particles led to a maximum improvement of 58.99%, 25.62%, 41.56%, and 47.83% in flexural strength and modulus, interply shear strength, and compression strength, respectively, compared to the pristine composites. Stress-strain curves confirmed that the core-shell particles delayed matrix and interlaminar crack propagation. Furthermore, micrographic images indicated improved interaction of CSPs at the ply interfaces. These findings can improve the interply strength of thermoplastic composites and assist designers in achieving higher performance. Full article

Due to their mechanical robustness and chemical resistance, composite electrospun membranes based on polyvinyl chloride (PVC) are suitable for sensor applications. Aiming to improve the electrical characteristics of these membranes, this work investigated the effects of the addition of carbon nanotubes (CNTs) to PVC electrospun membranes, in terms of morphology and thermal and impedance behavior. Transmission electron microscopy images evidenced that most of the nanotubes were encapsulated within the fibers and oriented along them, while field-emission scanning electron micrographs revealed that the membranes consisted of uniform fibers with an average diameter of 339 ± 31 nm, regardless of the addition of the carbon nanotubes. With respect to the neat resin, the addition of nanotubes caused a significant lowering of the glass transition temperature (up to 20 °C) and a marked change in the second degradation step of PVC. Nyquist plots from electrical impedance spectra showed a charge transfer resistance (R_CT) of 38 and 40 MΩ for neat PVC and PVC/CNT 3 wt.% membranes, respectively, indicating that, in the dry state, the encapsulation of CNTs in the fibers and the high porosity of the membranes prevented the formation of a percolation network, increasing the electrical resistance. In the wet state, however, there was a greater change in the impedance behavior, decreasing the resistance R_CT to 4.5 and 1.1 MΩ, for neat PVC and PVC/CNT 3 wt.% membranes, respectively. The results of this study, showing a significant variation in impedance behavior between dry and wet membranes, are relevant for the development of various types of sensors based on PVC composites. Full article

Reliable ballistic armor systems are crucial to ensure the safety of humans and vehicles. Typically, these systems are constructed from various materials like fiber-reinforced polymer composites, which are utilized for a favorable weight to ballistic protection ratio. In particular, there has been a quest for eco-friendly materials that offer both strong mechanical properties and sustainable advantages. The present work conducted a ballistic analysis of epoxy matrix composites using raffia (Raphia vinifera) fibers from the Amazon region as reinforcement. The experiments investigated the limit and residual velocities of composites with 10, 20, and 30 vol% of raffia. The experimental density of the composites was lower than that of the epoxy. Fractured surfaces were examined by scanning electron microscopy (SEM) to reveal the failure mechanism. The results showed that composites with 10 vol% raffia fiber fabric had the highest ballistic energy absorption (168.91 J) and limit velocity (201.43 m/s). The ones with 30 vol% displayed a higher level of physical integrity. The SEM micrographs demonstrated the failure mechanisms were associated with delamination and fiber breakage. There was a small variation in residual velocity between the composites reinforced with 10, 20, and 30 vol% of raffia, with 826.66, 829.75, and 820.44 m/s, respectively. Full article

This article investigates the activation of surface groups of poly(ethylene terephthalate) (PET) fibers in woven fabric by hydrolysis and their functionalization with chitosan. Two types of hydrolysis were performed—alkaline and enzymatic. The alkaline hydrolysis was performed in a more sustainable process at reduced temperature and time (80 °C, 10 min) with the addition of the cationic surfactant hexadecyltrimethylammonium chloride as an accelerator. The enzymatic hydrolysis was performed using Amano Lipase A from Aspergillus niger (2 g/L enzyme, 60 °C, 60 min, pH 9). The surface of the PET fabric was functionalized with the homogenized gel of biopolymer chitosan using a pad–dry–cure process. The durability of functionalization was tested after the first and tenth washing cycle of a modified industrial washing process according to ISO 15797:2017, in which the temperature was lowered from 75 °C to 50 °C, and ε-(phthalimido) peroxyhexanoic acid (PAP) was used as an environmentally friendly agent for chemical bleaching and disinfection. The influence of the above treatments was analyzed by weight loss, tensile properties, horizontal wicking, the FTIR-ATR technique, zeta potential measurement and SEM micrographs. The results indicate better hydrophilicity and effectiveness of both types of hydrolysis, but enzymatic hydrolysis is more environmentally friendly and favorable. In addition, alkaline hydrolysis led to a 20% reduction in tensile properties, while the action of the enzyme resulted in a change of only 2%. The presence of chitosan on polyester fibers after repeated washing was confirmed on both fabrics by zeta potential and SEM micrographs. However, functionalization with chitosan on the enzymatically bioactivated surface showed better durability after 10 washing cycles than the alkaline-hydrolyzed one. The antibacterial activity of such a bio-innovative modified PET fabric is kept after the first and tenth washing cycles. In addition, applied processes can be easily introduced to any textile factory. Full article

Precise measurement of fiber diameter in animal and synthetic textiles is crucial for quality assessment and pricing; however, traditional methods often struggle with accuracy, particularly when fibers are densely packed or overlapping. Current computer vision techniques, while useful, have limitations in addressing these challenges. This paper introduces a novel deep-learning-based method to automatically generate distance maps of fiber micrographs, enabling more accurate fiber segmentation and diameter calculation. Our approach utilizes a modified U-Net architecture, trained on both real and simulated micrographs, to regress distance maps. This allows for the effective separation of individual fibers, even in complex scenarios. The model achieves a mean absolute error (MAE) of $0.1094$ and a mean square error (MSE) of $0.0711$, demonstrating its effectiveness in accurately measuring fiber diameters. This research highlights the potential of deep learning to revolutionize fiber analysis in the textile industry, offering a more precise and automated solution for quality control and pricing. Full article

This study investigates the physical, mechanical, and structural characteristics of handmade paper samples derived from cellulose extracted from grass clippings using two distinct methods as follows: (1) alkali treatment and (2) alkali treatment followed by bleaching, coupled with the incorporation of barium sulfate as a mineral filler. Our investigation revealed that the handmade paper samples’ densities, moisture contents, and thicknesses varied within the ranges of 0.436 to 0.549 g/cm³, 5.60 to 2.51%, and 0.41 to 0.50 mm, respectively. The tensile strength and folding endurance of the papers produced through alkali treatment with barium sulfate were notably superior to those produced from bleached pulp and barium sulfate. Our analysis indicates that several critical factors, including paper density, thickness, the crystallinity index, and the microfibrillar structure of cellulose, intricately influence the mechanical and strength properties of the samples. Using Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) techniques, we identified characteristic cellulose bonds and examined cellulose’s crystalline and amorphous phases. Additionally, the crystallinity index of the samples was determined using both the Segal and peak deconvolution methods. Scanning electron microscopy (SEM) micrographs revealed interconnected networks of cellulose fibers with varying thicknesses and lengths, along with incorporated mineral filler within the cellulose fiber structure. Variations in mineral particle retention were attributed to the presence or absence of cellulose microfibrils. These findings contribute to our understanding of the observed strength characteristics of the paper samples and underscore the potential applications of cellulose derived from grass clippings, especially when combined with barium sulfate as a mineral filler in paper production. Full article

This study investigated the influence of fiber loading and maleated polyethylene (MAPE) coupling agent on the structural, thermal, mechanical, morphological properties, and torque rheology of high-density polyethylene (HDPE) reinforced with Posidonia oceanica fiber (POF) composites. HDPE/POF composites, both with and without MAPE, were manufactured using a two-step process: composite pellets extrusion, followed by test samples injection molding with various POF loadings (0, 20, 30, and 40 wt%). HDPE/POF composites reinforced with higher loading of POF (40 wt%) exhibit superior stiffness, better crystallinity, and higher stabilized torque and mechanical energy (E_m) compared to other composite formulations. Therefore, varying the POF loading leads to extrusion and injection processing variations. Furthermore, the coupling agent significantly enhances the tensile strength, ductility, impact strength, crystallinity, stabilized torque, and E_m of the HDPE/POF composite. This improvement is due to the enhanced interfacial adhesion between the POF and the HDPE matrix with the addition of the MAPE, as supported by the Scanning Electron Microscopy (SEM) micrographs. Full article

The high production rate of fossil-based plastics, coupled with their accumulation and low degradability, is causing severe environmental problems. As a result, there is a growing interest in the use of renewable and natural sources in the polymer industry. Specifically, rice bran is a highly abundant by-product of the agro-food industry, with variable amounts of protein and starch within its composition, which are usually employed for bioplastic development. This study aims to valorize rice bran through the production of nanofiber membranes processed via electrospinning. Due to its low solubility, the co-electrospinning processing of rice bran with potato starch, known for its ability to form nanofibers through this technique, was chosen. Several fiber membranes were fabricated with modifications in solution conditions and electrospinning parameters to analyze their effects on the synthesized fiber morphology. This analysis involved obtaining micrographs of the fibers through scanning electron microscopy (SEM) and fiber diameter analysis. Potato starch membranes were initially investigated, and once optimal electrospinning conditions were identified, the co-electrospinning of rice bran and potato starch was conducted. Attempts were made to correlate the physical properties of the solutions, such as conductivity and density, with the characteristics of the resulting electrospun fibers. The results presented in this study demonstrate the potential valorization of a rice by-product for the development of bio-based nanofibrous membranes. This not only offers a solution to combat current plastic waste accumulation but also opens up a wide range of applications from filtration to biomedical devices (i.e., in tissue engineering). Full article

Nanofibers made of natural proteins have caught the increasing attention of food scientists because of their edibility, renewability, and possibility for various applications. The objective of this study was to prepare nanofibers based on pumpkin leaf protein concentrate (LPC) as a by-product from some crops and gelatin as carriers for vitamin B12 using the electrospinning technique. The starting mixtures were analyzed in terms of viscosity, density, surface tension, and electrical conductivity. Scanning electron micrographs of the obtained nanofibers showed a slight increase in fiber average diameter with the addition of LPC and vitamin B12 (~81 nm to 109 nm). Fourier transform infrared spectroscopy verified the physical blending of gelatin and LPC without phase separation. Thermal analysis showed the fibers had good thermal stability up to 220 °C, highlighting their potential for food applications, regardless of the thermal processing. Additionally, the newly developed fibers have good storage stability, as detected by low water activity values ranging from 0.336 to 0.376. Finally, the release study illustrates the promising sustained release of vitamin B12 from gelatin-LPC nanofibers, mainly governed by the Fickian diffusion mechanism. The obtained results implied the potential of these nanofibers in the development of functional food products with improved nutritional profiles. Full article