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Natural fibers, especially lignocellulosic fibers extracted from plants, are gaining attention as polymer-matrix composite (PMC) reinforcements due to their comparative advantages over synthetic fibers. Natural fibers are relatively low cost, renewable, and biodegradable. Their production systems are associated with low equipment wear and are energy efficient. In addition, the incorporation of lignocellulosic fibers into PMCs may significantly improve some mechanical properties. This article presents an overview of the advantages and drawbacks of applying natural fibers, some of them relatively unknown, as reinforcements of PMCs. The mechanical behavior of composites incorporated with selected fibers is discussed in terms of the effect of surface micromorphology and the fiber/matrix interaction.

Helical springs are indispensable mechanical parts widely used in industry. Lightweight is one of the development trends of helical springs. In this study, three kinds of lightweight polymer matrix composite helical springs (PMCHSs) with unidirectional, multistrand, and wrapped textile structural reinforcement (PMCHS-U, PMCHS-M, and PMCHS-W) were designed, manufactured, and evaluated. The performance of these PMCHSs and the relationship between their performance and their corresponding polymer matrix composite spring wire rods (PMCRs) were studied through the torsion test of the PMCRs and the compression and resilience tests of the PMCHSs. The results showed that the performance of the PMCHSs could be effectively improved by using the wrapped structure as the reinforcement. The compression capacity of PMCHS-W was 72.6% and 137.5% higher than that of PMCHS-M and PMCHS-U, respectively. The resilience performance of the PMCHSs decreased with the increase in the spring constant. The performances of the PMCHSs and a steel spring were compared. The results showed that the spring constant of the steel spring could be achieved when the masses of PMCHS-U, PMCHS-M, and PMCHS-W were only 75%, 63%, and 49% of the mass of the steel spring, respectively. This research is of great significance to the improvement in lightweight spring performance.

Carbon fiber-reinforced polymers are considered a promising composite for many industrial applications including in the automation, renewable energy, and aerospace industries. They exhibit exceptional properties such as a high strength-to-weight ratio and high wear resistance and stiffness, which give them an advantage over other conventional materials such as metals. Various polymers can be used as matrices such as thermosetting, thermoplastic, and elastomers polymers. This comprehensive review focuses on carbon fiber-reinforced thermoplastic polymers due to the advantages of thermoplastic compared to thermosetting and elastomer polymers. These advantages include recyclability, ease of processability, flexibility, and shorter production time. The related properties such as strength, modulus, thermal conductivity, and stability, as well as electrical conductivity, are discussed in depth. Additionally, the modification techniques of the surface of carbon fiber, including the chemical and physical methods, are thoroughly explored. Overall, this review represents and summarizes the future prospective and research developments carried out on carbon fiber-reinforced thermoplastic polymers.

Highly thermally conductive boron nitride (BN)@ultra-high molecular weight polyethylene (UHMWPE) composites with the segregated structure were fabricated by powder mixing and hot pressing. Scanning electron microscopy and polarizing optical microscopy were used to analyze the dispersion of BN particles in the UHMWPE matrix. The morphology observation shows that BN particles are selectively located at the interfaces of UHMWPE particles and form continuous thermally conductive networks after the compression molding process. As a result, the thermal conductivity of the BN@UHMWPE composite increases to 3.37 W m  K with 38.3 vol% BN, which is seven times larger than that of the pure UHMWPE. Furthermore, the incorporation of BN also influences the crystallinity and thermal properties of UHMWPE.

This work proposes a facile fabrication strategy for thermally conductive graphite nanosheets/poly(lactic acid) sheets with ordered GNPs (o-GNPs/PLA) via fused deposition modeling (FDM) 3D printing technology. Further combinations of o-GNPs/PLA with Ti3C2Tx films prepared by vacuum-assisted filtration were carried out by “layer-by-layer stacking-hot pressing” to be the thermally conductive Ti3C2Tx/(o-GNPs/PLA) composites with superior electromagnetic interference shielding effectiveness (EMI SE). When the content of GNPs was 18.60 wt% and 4 layers of Ti3C2Tx (6.98 wt%) films were embedded, the in-plane thermal conductivity coefficient (λ||) and EMI SE (EMI SE||) values of the thermally conductive Ti3C2Tx/(o-GNPs/PLA) composites significantly increased to 3.44 W·m–1·K–1 and 65 dB (3.00 mm), increased by 1223.1% and 2066.7%, respectively, compared with λ|| (0.26 W·m–1·K–1 ) and EMI SE|| (3 dB) of neat PLA matrix. This work offers a novel and easily route for designing and manufacturing highly thermally conductive polymer composites with superior EMI SE for broader application.

Additive Manufacturing technology has a significant impact on the modern world because of its ability to fabricate highly complex computerized geometrics. Pure 3D-printed polymer parts have limited potential applications due to inherently inferior mechanical and anisotropic properties. For more utilization and versatility, the addition of fillers has enhanced their functionalities. 3D printing has innovative advantages including low cost, minimal wastage, customized geometry, and ease of material change. This review reveals the development of 3D printing techniques of matrix composite materials with improving properties and their applications in the fields of aerospace, automotive, biomedical, and electronics. A general introduction is given on AM techniques mainly fused deposition modeling (FDM), Powder-liquid 3D printing (PLP), selective laser sintering (SLS), stereolithography (SLA), digital light processing (DLP), and robocasting. Process methodologies and behavior of different filler additives, reinforcement fibers, nanoparticles, and ceramic polymer composites are discussed. Also, some major issues of difficulty including printing parameters, homogeneous desperation of fillers, nozzle clogging due to filler aggregation, void formation, augmented curing time, and anisotropic attributes are addressed. In the end, some capabilities and shortcomings are pointed out for further development of 3D-printing technology.

In recent years, researchers across the globe have switched from synthetic fibers to natural fibers for the fabrication of composites. The desirable properties of natural fibers which attracted researchers, as well as academicians, are its low density, easy availability, environmentally friendly nature, biodegradability, and high specific strength. Hence in the last decade, there is tremendous progress in the development of natural fiber-reinforced composites for various industrial applications. The current review focused on the recent progress in natural fiber-reinforced polymer composite. The natural fibers discussed in this review are derived from leaves, namely pineapple, sisal, and abaca. The extraction and processing of these fibers are briefly outlined. The properties and application of natural fiber-reinforced composites are also addressed in this review. One of the drawbacks of natural fiber is its poor compatibility with the polymer matrix. The different treatment methods to improve the fiber-matrix interaction are also summarized in the present review.

Natural fibre reinforced plant structures are widely used in nature. These plant structures combine light weight with superior mechanical properties. The fibre orientations in plants are optimized to the occurring forces, especially to the bending of plants by wind forces. Therefore it is important to study the effect of fibre orientation to the mechanical properties of materials in a systematic experimental approach. In this study the effect of reinforcement fibre orientation on mechanical properties of bio-based lyocell-reinforced polypropylene composite was analysed. For this purpose, special technique to produce composites with defined fibre orientation and fibre wetting was developed consisting of the production of intermingled hybrid yarn followed by defined yarn laying and thermoforming processes. The formed composites were subjected to tensile strength tests and dynamic mechanical analyses. The experimentally determined E-modulus was compared with values, calculated from the modified rule of mixture of Virk and Krenchel. The analysis showed that the experimental E-moduli were somewhat smaller than the theoretical values, which is indicative of a less than perfect interfacial bonding between the fibres and matrix. The influence of water on the composite performance was also analysed. It was shown that the composites sorb approximately 30% water by weight, and it has a strong influence on the E-modulus and other performance parameters. Graphical abstract

Fused deposition modeling (FDM) based 3D printing) technique involves the fabrication of polymer parts using a thermal process which may induce residual stress, stress concentration, distortion, and the delamination between layers. This paper aims to investigate this defect on ASTM D638 polymer composite specimens. For that purpose, a 3D thermo-mechanical model that simulates the process of FDM capable of calculating stresses and temperature gradients during the additive manufacturing of polymer composites was developed. The 3D model considers the temperature-dependent physical properties of composites which consist of density, thermal conductivity, thermal expansion coefficient, yield stress, and Young’s modulus. The simulated process includes the heating, solidification, and cooling phases. Different printed parts were analyzed and compared. The stresses vary continuously because of the temperature gradient occurring through the composite thickness. It appears that the concentration of stresses is higher if the temperatures during printing vary rapidly. Those stresses can favor the delamination between the layers of the printed part and the residual thermal stresses can cause an offset to the failure envelope.

In this research the effect of adding silicon carbide nano whiskers (SiCw) into epoxy resin and the impact of reinforcing surface treated SiC wire-mesh (SiCwm) and woven aloevera/hemp/flax fibers (NF) were studied. The principal aim of this work was demonstrating the importance of adding SiCw (0.5 and 1.0 vol.%) and SiC wire-mesh with economical natural fibres (50 vol.%) and silane surface treatment on natural fibres in mechanical and low velocity impact behavior. The SiCw and natural fibres were surface treated by 3-Aminopropyltriethoxysilane whereas SiC wire-mesh was shot blasted. The composites were cured at room temperature using an aliphatic hardener Triethylenetetramine (TETA). The strength factor results showed that the silane surface modified composite designation ‘H 4 ’ gave highest normalized strength of 98%. The highest tensile and flexural strength of 141 and 240 MPa was observed for silane surface modified composite designation ‘H 4 ’. The low velocity impact damage behavior of ‘H 4 ’ composite designation showed higher resistance against to penetration. Transmission electron microscope (TEM) morphological images showed uniform dispersion of surface-modified SiCw in epoxy resin. Similarly the silane treated natural fibre and shot blasted SiC wire-mesh given improved adhesion with matrix. These high damping polymer composites offers their application in automobile, structural and domestic sector.