Search

Excellent recycled carbon fiber (rCF) was obtained using a thermally activated oxide semiconductor process. An alignment device was manufactured based on wet‐laid technology. It was used to investigate the effect of various alignment nozzle parameters on the degree of alignment of rCF mats. The mechanical, electrical conductivity and EMI shielding properties of composites reinforced by rCF mats with different layup structures were analyzed. The results showed that the optimal alignment parameters for rCF aligned mats included a convex nozzle shape, a nozzle diameter of 3 mm, a nozzle channel length of 50 mm, a nozzle up‐and‐down diameter ratio of 7:1, a nozzle departure height of 20 mm. These settings achieved a preferential alignment degree (PAD) of 93.07%. The design of layup structures for rCF mats with optimized fiber alignment fully exploits the material's anisotropic characteristics. The rCF‐0/EP composite material exhibited the highest tensile strength (195.45 MPa), while the rCF‐04/EP composite material not only demonstrated the highest flexural strength (247.95 MPa) but also showed excellent electromagnetic interference (EMI) performance (47.97 dB). The results of the research laid a theoretical foundation and provides scientific guidance for high‐value reuse of rCF. Highlights: Utilized rCF as a reinforcing material for CFRP composites.Preparation of rCF aligned mats with high PAD.Effect of different layup structures on rCF aligned mat reinforced composites.rCF aligned mats improve mechanical properties and EMI properties of composites. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the influence of dammar resin on the mechanical properties of composite materials reinforced with corn husk and paper waste laminates. Different percentages of dammar resin (50%, 60%, and 70%) were added to the matrix while keeping the reinforcement constant. For all samples, the ratio was maintained at 40% matrix and 60% reinforcement. With the experimental results obtained, statistical analyses were conducted: two-way analysis of variance (ANOVA), Levene's test, Shapiro-Wilk test, and ANOVA post hoc (with Bonferroni correction). The null hypothesis stated that dammar resin does not influence the mechanical properties. For all tests considered, the null hypothesis was rejected (p < 0.05), the variances were homogeneous (p > 0.05), and the data followed a normal distribution (p > 0.05). It was found that dammar resin had a significant influence on the mechanical properties as the percentage increased from 50% to 70% (p < 0.0083). For each test, based on already known premises, an explanation of the phenomenon that could occur due to the insertion of dammar resin was provided, serving to complement and validate the statistical estimations. [ABSTRACT FROM AUTHOR]

In last two decades the intensive growth in the number of publications devoted to plant fibers as reinforcements for polymer matrices is observed. Considering ecological issues natural fibers are recognized as an appealing alternative to synthetic ones. Unlike hemp fiber, which is frequently used for given needs, its by-product named hemp woody core (HWC) has not yet gained much scientific attention in this sphere. Nevertheless, owing to the set of its unique properties HWC is also may be a promising filler. Application of HWC in composites would additionally contribute to its proper utilization. However, among the distinctions of lignocellulosic reinforcements is their hydrophilicity that requires to be reduced to ensure strong interface interaction with the matrix and good durability of the resulting composites. Herein, mercerization (alkali treatment) and/or subsequent modification of HWC with epoxidized soybean oil (ESO) or 3-aminopropyltriethoxysilane (APS) was used for this purpose. Si-containing epoxyurethane polymer matrix was synthesized from sodium silicate, polyisocyanate and ESO as epoxy component. Four series of molded samples with high plant filler content (60 wt. %) were elaborated. The results of contact angle and water uptake measurements showed that all applied types of treatment led to hydrophobization of the surface. Thus, the values of contact angles of composites with modified HWC exceeded 90 °, and their surface energy was lower than the one of neat samples. Regardless of quite high polarity of composites containing silanized HWC due the presence of amino and silanol groups, the formation of covalent bonds between filler and APS coupling agent turned out to be crucial for such characteristics as water resistance and mechanical performance. Particularly, equlibrium moisture content decreased by 31 % compared to that of the samples with pristine HWC, whereas tensile and flexural strength improved by 19 and 65 %, respectively. The highest microbial stability of the specimens with silane treated filler estimated within soil burial test is another evidence of enhanced interfacial adhesion in this case. [ABSTRACT FROM AUTHOR]

Composite materials have gained significant attention in various engineering fields due to their unique mechanical properties and versatility. This review focuses on the torsional properties of composite materials, exploring the fundamental aspects that govern their behavior when subjected to torsional loads. Torsional properties, including shear modulus, fiber orientation, anisotropy, torsional strength, manufacturing considerations, and testing methodologies, are examined in detail. Understanding the torsional behavior of composites is crucial for optimizing their performance in applications ranging from aerospace to sports equipment. This review paper provides a concise overview of the key considerations and parameters involved in assessing the torsional properties of composite materials, offering a foundation for further research and application in this field. [ABSTRACT FROM AUTHOR]

Energy harvesting systems fabricated from rubber composite materials are promising due to their ability to produce green energy with no environmental pollution. Thus, the present work investigated energy harvesting through piezoelectricity using rubber composites. These composites were fabricated by mixing titanium carbide (TiC) and molybdenum disulfide (MoS 2 ) as reinforcing and electrically conductive fillers into a silicone rubber matrix. Excellent mechanical and electromechanical properties were produced by these composites. For example, the compressive modulus was 1.55 ± 0.08 MPa (control) and increased to 1.95 ± 0.07 MPa (6 phr or per hundred parts of rubber of TiC) and 2.02 ± 0.09 MPa (6 phr of MoS 2 ). Similarly, the stretchability was 133 ± 7% (control) and increased to 153 ± 9% (6 phr of TiC) and 165 ± 12% (6 phr of MoS 2 ). The reinforcing efficiency (R.E.) and reinforcing factor (R.F.) were also determined theoretically. These results agree well with those of the mechanical property tests and thus validate the experimental work. Finally, the electromechanical tests showed that at 30% strain, the output voltage was 3.5 mV (6 phr of TiC) and 6.7 mV (6 phr of MoS 2 ). Overall, the results show that TiC and MoS 2 added to silicone rubber lead to robust and versatile composite materials. These composite materials can be useful in achieving higher energy generation, high stretchability, and optimum stiffness and are in line with existing theoretical models.

Composites based on powdered single-component epoxy matrix are an alternative technological solution for composites produced using liquid epoxy resins. This article describes in detail the process of producing graphite-reinforced composites for tribological applications. The advantages and disadvantages of technological processes where the matrix is a single-component epoxy powder were demonstrated, and the properties of the obtained materials were examined. A series of composite materials with the graphite filler with sizes below 10 μm and below 45 μm and weight additions of 5, 10, 20, 30% were produced. Mechanical tests and tribological tests conducted with the pin-on-block method were performed, and the mechanism of tribological wear was described. The conducted research allowed us to conclude that the incorporation of graphite, regardless of particle size, above 10% by weight results in a significant reduction in the friction coefficient (approximately 40-50% lower than in unfilled epoxy resin), which is beneficial in the production of cheap self-lubricating materials.

The localized stress and strain field simulation results are critical for understanding the mechanical properties of materials, such as strength and toughness. However, applying off-the-shelf machine learning or deep learning methods to a digitized microstructure restricts the image samples to be of a fixed size and also lacks interpretability. Additionally, existing methods that utilize deep learning models to solve boundary value problems require retraining the model for each set of boundary conditions. To address these limitations, we propose a customized Pixel-Wise Convolutional Neural Network (PWCNN) to make fast predictions of stress and strain fields pixel-by-pixel under different loading conditions and for a wide range of composite microstructures of any size (e.g., much larger or smaller than the sample on which the PWCNN is trained). Through numerical experiments, we show that our PWCNN model serves as an alternative approach to numerical solution methods, such as finite element analysis, but is computationally more efficient, and the prediction errors on the test microstructure are around 5%. Moreover, we also propose an interpretable machine learning framework to facilitate the scientific discovery of why certain microstructures have better or worse performance than others, which has important implications in the design of composite microstructures in advanced manufacturing.

This research is conducted to improve the performance of plant fiber-based composites by inserting microcrystalline cellulose (MCC). MCC was incorporated into a mixture of recycled high-density polyethylene (rHDPE) and cantala fiber at a ratio of 1, 2, 3, and 4% wt. The composites rHDPE/cantala fiber/MCC were fabricated via a twin screw extruder followed by a hot press. The composite’s mechanical, physical, and thermal properties were tested to investigate the effect of adding MCC. It was observed that the enhancement of MCC led to a significant improvement in the mechanical performance of the composite. Adding 4%wt MCC resulted in a significant improvement in mechanical properties of 50.7%, 31%, and 37.7%, respectively, in tensile strength, bending strength, and impact strength compared to rHDPE/cantala composite without MCC. Adding MCC up to 4% wt slightly increased the composite density from 0.88gr/cm3 to 0.90 gr/cm3. The enhancement of MCC did not significantly change the diffraction peak position of the composite. However, composite crystallinity increased by 6.7%. In addition, the augment of MCC increased the thermal stability of the composite, as indicated by the delay in composite degradation.

Periodic boundary condition is commonly used in the FE homogenization method for predicting the thermo-mechanical properties of composites. However, its existing numerical algorithms are generally inefficient. Linear displacement boundary condition is much easier and more efficient to implement for the Representative Volume Elements (RVEs) with conformal and nonconformal surface meshes. Aiming at replacing the periodic boundary condition by the linear displacement boundary condition to easily and efficiently predict the thermo-mechanical properties of composites, this paper compares the implementation efficiency and prediction accuracy of the periodic and linear displacement boundary conditions. Regarding the prediction of the elastic properties of composites, the balance of micro-energy and macro-energy of the RVEs imposed the periodic and linear displacement boundary conditions is checked, and the results demonstrate that these two boundary conditions guarantee the Hill lemma (i.e. the balance of micro-energy and macro-energy of the RVEs). Moreover, comparing with the experimental test and the multi-step micro-mechanical method, the effectiveness of the periodic and linear displacement boundary conditions to predict the elastic properties of composites is validated. [ABSTRACT FROM AUTHOR]

This paper presents the results of tests concerning the castability of metal composites based on an aluminium alloy matrix. The castability of composite suspensions containing carbide particles and suspensions containing graphite particles was tested using two tests: spiral and rod tests. It was found that as the volume fraction of particles increases, the castability of composites decreases, with graphite particles having a greater effect on the decrease in castability than silicon carbide particles. The paper also presents the results of research concerning the effect of ceramic particles on the shrinkage of solidifying and cooling composites. The shrinkage test results show a positive effect of ceramic particles introduced into the aluminium alloy, manifested by a decrease in the shrinkage value.