Mechanical Properties Of Composites Research Articles

Determining the characteristics of representative volume elements in severely deformed aluminum-matrix composite

The accurate evaluation of the effective mechanical properties of composites mainly depends on the characteristics of representative volume elements (RVEs). This paper mainly investigates the RVE size. Additionally, the effect of volume fraction of reinforcement, the edge effect, and RVE types on the critical size are discussed. First, the Al/Ni multilayered composites were processed by nine cycles of the cross-accumulative roll bonding (CARB) method. Then, one type of RVEs was created based on cross-sectional micrographs of composites to consider their inhomogeneities. Another type was generated by using the random sequential adsorption (RSA) procedure. Thereafter, the homogenized effective elastic properties of both types of microstructure-based RVEs and RSA-based RVEs were computed and compared as a function of the volume fraction of Ni and RVE size. The results showed that by increasing the Ni fragments, the RVEs indicated stiffer elastic behavior. By increasing the volume fraction of Ni from 0.2 Vf to 0.8 Vf, the Poisson ratio decreased by 7 % and the elastic modulus increased by 83 % for RSA-based RVE. Regarding the size of microstructure-based RVE of Al/Ni (0.8 Vf), from the largest size (size 1) with a length of 575 μm and a width of 575 μm to the smallest size (size 5) with a length of 287.5 μm and a width of 287.5 μm, the elastic modulus and the Poisson ratio showed 16 % and 0.8 % decrease, respectively.

Fabrication of the Cu/AgCuTi/Nb composite for superconducting radio-frequency material under extreme service conditions based on electroplating additive manufacturing

The primary objective of this study is the development of Cu/Nb composite materials for Superconducting Radio-Frequency (SRF) applications under extreme service conditions characterized by a strong RF electromagnetic field, extremely low temperatures, and relatively low heat loss. A novel integrated manufacturing approach is proposed, which combines cold-sprayed AgCuTi alloy as an intermediate coating on the Nb surface and an electroplated Cu layer with a subsequent heat treatment brazing effect. This strategy aims to address the significant challenge of non-intermelting Cu and Nb while also considering effective lateral heat transfer. Mechanical property tests showed that the bond strength of Nb/AgCuTi/Cu composites exceeded 150 MPa. Low-temperature thermal transport tests indicate that the Residual Resistance Ratio (RRR) of the Cu layer surpasses 150, with a thermal conductivity at 4.2 K exceeding 1600 W/(m·K). Moreover, both the composite interface and mechanical properties of the specimens remain stable even after undergoing cyclic cold shock experiments. These findings suggest that the Nb/AgCuTi/Cu composite material developed in this study meets the technical requirements for long-term stable and high-performance operation in high-current and high-power superconducting accelerators.

Investigation on mechanical properties of bronze infill PLA composite fabricated by fused deposition modelling

This study is on the mechanical properties of bronze infill poly lactic acid composites fabricated by fused deposition modelling. By changing the nozzle temperature, printing speed, layer thickness and infill density the mechanical properties of the composites were studied. Tensile, flexural and impact strength tests were conducted on the composite specimen. Mathematical models were developed using response surface methodology and the significance of the models was tested using analysis of variance. Increase in infill density and nozzle temperature increased the strengths of the composites. Increase in layer thickness and printing speed decreased the strengths of the composite specimen. Tensile strength is primarily influenced by infill density (38.82%), flexural strength is primarily influenced by Nozzle Temperature contributes (44.02%) while Infill density (58.12%) plays the major role in contributing the impact strength followed by other parameters. The highest tensile strength, flexural strength, impact strength values obtained in this study are 19.3 (N/mm2), 36.08 (N/mm2) and 0.26 (kJ/m2) respectively. The mechanism of the fractured specimen was investigated using scanning electron microscopy. Fracture mechanisms such as cracks, infill gaps, voids, interface, delamination, hillocks, particle pull out, delamination had an effect on the fracture of composite specimens.

Introduction to Polymer Composites in Aerospace

The strategic use of polymer composites in aerospace engineering has influenced aircraft and spacecraft design and manufacturing. This abstract summarizes the fundamental principles, key components, and significance of polymer composites in aerospace applications. Polymer composites are formed of a matrix material (generally a polymer resin) reinforced with high-strength fibres like carbon, glass, or aramid. This combination gives the composite superior mechanical properties, such as high strength-to-weight ratio, stiffness, and resistance to fatigue and corrosion. Such properties make polymer composites ideal for aerospace structures where lightweight construction and exceptional performance are critical.Polymer composites are widely used in aerospace to reduce weight, improve fuel efficiency, and strengthen structural integrity in structural components such as wings, empennages, and fuselages. They are also essential to propulsion systems, interior structures, and thermal protection systems, which emphasizes their adaptability and versatility to a wide range of aerospace applications.The use of polymer composites in aerospace has driven improvements in manufacturing processes, including automated resin transfer molding and fibre placement, making it possible to produce intricate composite structures with extreme efficiency and precision. Furthermore, engineers can maximize component performance while adhering to strict aerospace regulations and safety standards thanks to the design flexibility provided by polymer composites.Further study attempts to boost the capabilities and characteristics of polymer composites, such as better resistance to damage, durability to impacts, and durability in extreme conditions. The invention of the next-generation aerospace vehicles that can meet the changing needs of space exploration and transportation looks promising as a result of this ongoing innovation.

A review of the formability of woven fabrics for composite materials

AbstractTextile composites are advanced materials composed of preforms combined with matrix materials. The fiber structure in the preform has a significant impact on the mechanical properties of the composite. Precise control over preform dimensions and internal fiber structural uniformity, termed ‘accurate shape control’, is essential to ensure reliable and stable composite component mechanical properties. This paper reviews current research progress on fabric deformation mechanisms, focusing on experimental characterization and numerical simulation. Experimental methods for fabric deformation include tensile, compression, bending, and shear deformation, whereas numerical methods encompass macroscopic continuum, discrete, and semi‐discrete models. The insights offered in this paper will aid a greater understanding of fabric deformation mechanisms, enabling an accurate prediction of complex shape molding and effective process parameter design, ultimately facilitating the structural design and engineering applications of textile composites.Highlights Recent trends and challenges in the study of fabric deformation mechanisms are presented. The experimental methods for fabric deformation were summarized and evaluated. Representative numerical modeling techniques and simulation methods are discussed. Some recommendations on potential future research directions are detailed.

Characterization and mechanism analysis of interfacial shear strength between individual aramid fiber and epoxy by oxygen plasma treatment at elevated temperatures: Experiment and simulation

The weak adhesion between aramid fibers Ⅲ and the resin matrix, due to its smooth surface and high inertness of the fibers. This property restricts the mechanical properties of the composites in high temperatures environments. This work describes the treatment of aramid fibers Ⅲ with oxygen plasma to introduce reactive oxygen-containing functional groups onto fiber surface. The analysis focused on the impact of interfacial friction and interfacial wettability on the transfer of load across composites at various temperatures. According to the X-ray photoelectron spectroscopy (XPS) analysis, the fiber surface showed an increase in the number of active groups after plasma treatment. In addition, two new oxygen-containing functional groups -C-O- and -O-CO appeared. The use of Scanning Electron Microscopy (SEM) and atomic Force Microscopy (AFM) showed that the plasma treatment has an etching effect on the fiber surface and increases the roughness of the fiber surface. Furthermore, after plasma treatment, the fibers adhered to the resin matrix through hydrogen bonding and π-π bonding. The utilization of this technique led to a significant enhancement in the interfacial properties of monofilament composites across various temperature ranges. The IFSS of plasma-treated aramid fiber Ⅲ/EP exhibited increases of 38 % at the test temperature of 25℃. Surprisingly, the IFSS of plasma-treated aramid fiber III/EP exhibited a significant increase of 52 % at the test temperature of 120℃. In this paper, COMSOL software was utilized to simulate the IFSS before and after plasma treatment at different temperatures. Mechanistically explains the effect of temperature on the interfacial mechanical properties of composites.

High strength and self-lubrication graphite/SiC composites

For the reaction-formed graphite/SiC composites, the presence of cracks and poor mechanical properties seriously affect their reliability as wear resistant or sealing materials. In this work, a porous carbon preform was pressure formed first by carbon-composite-powder (PFC@G) and carbon black, impregnated with resin and carbonized subsequently, which can heal the micro-cracks, increased the strength of porous carbon preforms and finally reduce the reactivity of liquid Si and carbon during the reaction forming process. The results show that the modified porous carbon preform has a 4.8 % reduction in porosity and a 3.98 times increase in compressive strength. After reactive melt infiltration, the prepared graphite/SiC composites had a compact and isotropic structure and obtained the highest carbon content of 66.18 vol%. In addition, the coupling effect of the PFC@G size on the carbon content and mechanical properties of composites was studied. With the decreasing of the PFC@G size, the mechanical properties of the composites increased and the carbon content decreased. The sample with a carbon content of 48 vol% and a bending strength of 137 MPa exhibited excellent self-lubrication properties.

Innovative Approaches for Manufacturing Epoxy-Modified Wood and Cellulose Fiber Composites: A Comparison between Injection Molding and 3D Printing.

The current study focused on improving the properties of polylactic acid (PLA) for wider application in load-bearing scenarios. Various methods were explored to optimize the interaction between PLA and natural fibers, particularly wood fibers (WFs). Alkalized and epoxy-impregnated WFs were evaluated against untreated WFs and cellulose fibers in both injection molding (IM) and fused deposition modeling (FDM). FTIR analysis revealed the removal of hemicellulose and lignin in alkalized WFs and uniform epoxy curing. Addition of fibers reduced PLA's thermal stability while acting as nucleating agents. Additionally, fibers augmented the storage modulus of biocomposites, with alkalized fibers exhibiting the highest tensile modulus in IM. FDM samples with a 0° raster angle showed superior impact resistance compared to IM counterparts. Moreover, raster angle significantly influenced FDM biocomposite properties, enhancing the tensile strength and modulus of untreated WF and cellulose fibers at 0°. Although FDM did not produce alkalized WF samples, epoxy impregnation emerged as a promising method for enhancing PLA/WF composite mechanical properties in the IM process, offering valuable insights for composite material development.

Development of novel sustainable biocomposite from polycaprolactone and Sesbania rostrata fiber

AbstractAn efficient method to accelerate the use of polymer composites is to focus on their development as environmentally friendly materials that can naturally break down without causing any harm to the ecosystem. Hence, the primary aim of this study is to develop a biocomposite material through the fusion of Sesbania rostrata (SRF) bark fibers and the polycaprolactone (PCL) biopolymer. Various percentages (10, 15, 20, and 25 wt.%) of untreated and sodium bicarbonate‐treated SRF were incorporated into polycaprolactone to create the biocomposite samples. The composite panels were made using the compressing molding technique. Several tests were performed on the samples, such as mechanical, thermal, water absorption, wear, and morphological tests. Research has demonstrated that the strength of biocomposites composed of 20% chemically treated SRF and PCL is superior to that of other mixed materials. The thermal properties of the biocomposite remained unchanged when untreated fibers were included, but they improved when treated fibers were included. Higher water absorption properties are attributed to an increased fiber volume fraction in the biocomposites, while chemically treated fibers exhibit a notable improvement in water resistance. The wear test results indicate that the weight loss of the biocomposites is mainly influenced by the contact temperature and adhesion between the SRF surface and the PCL matrix. When examining the fractured biocomposites with a scanning electron microscope (SEM), it becomes evident that the primary reasons for failure are fiber pull‐out, debonding, and agglomeration.Highlights SR Natural fiber is chemically treated by eco‐friendly sodium bicarbonate. The treated SRF‐reinforced composites had best mechanical property. The treated SRF‐reinforced composites showed less water absorption. The composite mechanical and thermal properties had dropdown at 25 wt.% SRF. The addition of SRF reduced the weight loss of composites on wear test.

Predicting the modulus of elasticity of clayey soil composites reinforced with scrap tire rubber fibers using a composite material model

In this study, composite material models are used to predict the modulus of elasticity of a composite consisting of scrap tire rubber fibers and clayey soils. The calculated modulus of elasticity is compared with the reference modulus obtained from experimental testing. Predicting the effective mechanical properties of composites is crucial in situations where testing is impractical, challenging, or costly. The analysis involves various approaches within the elasticity framework, utilizing rheological models such as Voigt, Reuss, Hirsch-Dougill, Popovics, Halpin-Tsai, Hashin, and the Bache & Napper–Christensen estimation. These models aim to predict the effective Young's modulus of the composite system comprising soil and rubber fibers. The maximum discrepancies observed are 10.66%, 12.71%, and 12.98% for both soils. Voigt, Hashin, and Bache estimations provide highly accurate predictions of the effective Young's modulus, showing excellent agreement with experimental results across different fiber volume fractions ranging from 10% to 50%.

Microstructure and Mechanical Properties of Mg-Al-La-Mn Composites Reinforced by AlN Particles.

The Mg-Al-RE series heat-resistant magnesium alloys are applied in automotive engine and transmission system components due to their high-temperature performance. However, after serving at a high temperature for a long time, the Al11RE3 phase coarsened and even decomposed, while the Mg17Al12 phase grew and dissolved, which limits the service temperature of Mg-Al-RE series heat-resistant magnesium alloys to a maximum of 175 °C. In this study, a new preparation method for in situ AlN particles was presented. The AlN/Mg-4Al-4La-0.3Mn composites were prepared by a master alloy and casting method. The effects of various contents of AlN (0.5-3.0 wt.%) on the microstructure and mechanical properties of the Mg-4Al-4La-0.3Mn (AE44) alloy at room (25 °C) and high temperatures (150-250 °C) were investigated. Microstructure analysis revealed that the inclusion of AlN led to a reduction in both the grain size and second phase size in the AE44 alloy, while also improving the distribution of the second phase. The average grain size, Al11La3 phase, Al2La phase, and Al3La phase of the 2.0 wt.% AlN/AE44 composite were 135.7, 9.6, 1.9, and 12.6 μm, respectively, which were significantly lower than those of the AE44 matrix alloy (179.8, 12.6, 3.3, 17.8 μm). The refinement was attributed to the ability of AlN particles to serve as heterogeneous nucleation cores for α-Mg and, at the same time, impede the growth of the solid-liquid interface, eventually leading to grain refinement. With the increase in the AlN content, the mechanical properties of composites initially exhibited an increase at both room and high temperatures, followed by a subsequent decrease. When the AlN content was 2.0 wt.%, the composite exhibited optimal strength and plasticity matching. At room temperature, the TYS, UTS, and EL values of the 2.0 wt.% Mg-4Al-4La-0.3Mn composite were 96 MPa, 175 MPa, and 7.0%, respectively, which were increased by 26 MPa, 27 MPa, and 0.7% when compared with the base alloy. The TYS of the 2.0 wt.% Mg-4Al-4La-0.3Mn composite at 150 °C, 200 °C, and 250 °C were 17 MPa, 14 MPa, and 22 MPa higher than those of the matrix alloy, respectively. The main strengthening mechanisms were second phase strengthening, load transfer strengthening, and thermal mismatch strengthening. At elevated temperatures, AlN particles effectively pinned the grain boundaries, inhibiting their migration, and hindered dislocation climbing, resulting in excellent mechanical properties of the composites at high temperatures. This study contributes to the advancement of in situ AlN particle preparation methods and the exploration of effects of AlN on the properties and microstructure of Mg-Al-RE alloys at high temperatures (150-250 °C).

The Effect of Chopped Carbon Fibers on the Mechanical Properties and Fracture Toughness of 3D-Printed PLA Parts: An Experimental and Simulation Study

The incorporation of fiber reinforcements into polymer matrices has emerged as an effective strategy to enhance the mechanical properties of composites. This study investigated the tensile and fracture behavior of 3D-printed polylactic acid (PLA) composites reinforced with chopped carbon fibers (CCFs) through experimental characterization and finite element analysis (FEA). Composite samples with varying CCF orientations (0°, 0°/90°, +45°/−45°, and 0°/+45°/−45°/90°) were fabricated via fused filament fabrication (FFF) and subjected to tensile and single-edge notched bend (SENB) tests. The experimental results revealed a significant improvement in tensile strength, elastic modulus, and fracture toughness compared to unreinforced PLA. The 0°/+45°/90° orientation exhibited a 3.6% increase in tensile strength, while the +45°/−45° orientation displayed a 29.9% enhancement in elastic modulus and a 29.9% improvement in fracture toughness (259.12 MPa) relative to neat PLA (199.34 MPa√m). An inverse correlation between tensile strength and fracture toughness was observed, attributed to mechanisms such as crack deflection, fiber bridging, and fiber pull-out facilitated by multi-directional fiber orientations. FEA simulations incorporating a transversely isotropic material model and the J-integral approach were conducted using Abaqus, accurately predicting fracture toughness trends with a maximum discrepancy of 8% compared to experimental data. Fractographic analysis elucidated the strengthening mechanisms, highlighting the potential of tailoring CCF orientation to optimize mechanical performance for structural applications.

A scale-span method to characterize the mechanical property of BCF/PEEK considering uncertain structural characteristics

The focus of this study is exploring a scale-span characterization method to predict the mechanical properties of Braided Carbon Fiber Reinforced Poly Ether Ether Ketone (BCF/PEEK) considering structural uncertainty. Firstly, a complicated micro-scale Representative Volume Element (RVE) model that considers the random position and size of fiber was established via the developed Python script. Analogously, a mathematical expression adopted by the trust region algorithm was proposed to accurately describe the detailed cross-sectional shapes and fluctuation amplitude characteristics of BCF/PEEK for the sake of establishing the precision meso-scale RVE model. Then, the corresponding elastic properties that consider fiber volume fraction and fiber distribution location were characterized via the span-scale characterization method. Meanwhile, the influence of fiber bundle fluctuation amplitude and fiber volume fraction on the mechanical properties was investigated as well. In addition, the mechanical properties of BCF/PEEK with the change of the braid angle between warp and weft yarn were predicted via the established meso-scale RVE model. Finally, a series of experiments have been carried out. The maximum and minimum absolute prediction deviation of all elastic property parameters were only 4.07 % and 1.41 %, respectively, which verified the proposed scale-span characterization method can predict the mechanical properties of composites well.

Study on the microstructure and mechanical properties of hot rolled nano-ZrB2/AA6016 aluminum matrix composites by friction stir processing

In this paper, in-situ ZrB2/AA6016 particle-reinforced aluminum matrix composites were prepared in molten A6016 aluminum alloy melt by KBF4-Al- K2ZrF6 reaction system. For the first time, this paper presents that after casting, the composites would be subjected to large strain hot rolling (LSHR) with 60 % undercutting and then friction stir processing (FSP) with a stirred probe speed of 1200 r/min and a traveling speed of 60 mm/min. To study the microstructure and mechanical properties of composites strengthened by large strain hot rolling combined with friction stir processing. The results show that the tensile strength of the base material is 140.1 MPa, the elongation is 46.3 %, the product of strength and elongation reaches 6.5 GPa%, and the average hardness is 43.4 HV; The tensile strength of LSHR+FSP nugget zone is 163.4 MPa, the elongation is 78.9 %, the product of strength and elongation reaches 12.9 GPa %, which is about 98.6 % higher than the base material, and the average hardness is 59.8 HV, which is about 37 % higher than the base material. SEM, EBSD, and TEM analyses showed that the average grain size is refined from 189.7 μm to 3.8 μm after LSHR+FSP. The ZrB2 particles are sufficiently fragmented, with a particle size of about 20 nm, and uniformly dispersed in the matrix. This study provides the theoretical and experimental basis for applying nanoscale ZrB2 particles reinforcing ultrafine crystalline aluminum matrix composites prepared by LSHR + FSP.

Influence of phosphomolybdate modified with quaternary ammonium salts on enhancing the flame retardancy and antibacterial characteristics of epoxy resin/aluminum diethylphosphinate composites

In this work, we synthesized a series of compounds, denoted as xCTAB@AMP, by incorporating varying different molar fractions of cetyltrimethylammonium bromide (CTAB) into ammonium phosphomolybdate (AMP). The effects of CTAB modification on the surface characteristics, morphology and hygroscopicity of AMP were studied. Moreover, we explored the combined flame-retardant impact between xCTAB@AMP and aluminum diethylphosphinate (ADP) when incorporated into epoxy resin (EP), as well as the resulting composite's mechanical properties, thermal stability and antibacterial properties. The EP composite containing 50 molar percent CTAB-modified AMP (EP/50CTAB@AMP/ADP) demonstrated remarkable flame retardancy, achieving a UL-94 V-0 rating and increasing limiting oxygen index (LOI) to 30.0%. This formulation significantly lowered the peak heat release rate (PHRR) to 452 kW/m2, a 65% reduction to that of EP, and the total heat release (THR) to 68 MJ/m2, a 24% decrease to that of EP. Additionally, compared to EP, the peak smoke production rate (PSPR) of this composite was decreased by 30% (0.28 m2/s), the total smoke production (TSP) was reduced by 25% (30.2 m2), and peak carbon monoxide release rate (PCOP) was diminished by 34% (0.038 g/s). The combination of 50CTAB@AMP and ADP in the EP matrix exhibited an exceptional synergistic flame-retardant effect. Concurrently, the CTAB modification bolstered the interfacial interactions between AMP and the EP matrix, which enhanced the mechanical properties of EP/AMP/ADP composites. As a result, the tensile strength and elongation at break of the EP/50CTAB@AMP/ADP composite increased by 13% and 15%, respectively, compared to the EP/AMP/ADP. Moreover, the 50CTAB@AMP maintained its inherent antibacterial activity, which endowed the EP/50CTAB@AMP/ADP composite with a potent inhibitory effect against Staphylococcus aureus, a common pathogenic bacterium.

Improvement of silicon and epoxy phase interface by constructing rigid interpenetrating networks based on bismaleimide to enhance ablative, mechanical and thermal properties

Polysiloxanes are widely used in the preparation of ablative-resistant resins due to their tailored reactivity and ceramisable properties. Nevertheless, the mechanical and thermal properties may be negatively impacted by the presence of flexible chain segments and poor compatibility. In this study, the phase interface of silicon between epoxy was improved by a rigid interpenetrating crosslinked network constructing by bismaleimide. The pyrolysis of the silicone was inhibited and the oxidation resistance of the resin was enhanced. Both graphitization and ceramisation of the char layer during ablation are significantly improved. This endows the modified resin with outstanding ablative properties, with mass and linear ablation rates reduced to 0.0666 g/s and 0.0512 mm/s, respectively, which exceed those of some conventional ablative-resistant resins. Remarkably, the thermal and mechanical properties are significantly enhanced benefiting from the rigid crosslinked network and improved phase interfaces. Moreover, the destruction of mechanical properties of composites in high temperature environments caused by organosilicones has been effectively addressed. Bismaleimide/silicone co-modified epoxy resins can be used not only as ablative-resistant coatings, but also for the preparation of fire-resistant carbon fibre composites, providing a novel approach to the production of cost-effective, recyclable structural integrated materials for thermal protection.

Microstructure and mechanical properties of tungsten matrix composites synergistically reinforced with TiC-ZrC particles prepared by spark plasma sintering

In this paper, W-TiC-ZrC composites with extremely high strength were prepared by high-energy ball milling followed by spark plasma sintering. The microstructure morphology and structural evolution of the composites were thoroughly analyzed by SEM, EDS, EBSD, XRD, XPS and TEM, and the mechanical properties of the composites were accurately evaluated by microhardness tests and compression tests at room temperature and high temperatures. The results show that the micromorphology of W-TiC-ZrC composites changes from a spherical shape to an elongated shape with the increase of TiC-ZrC addition. Meanwhile, the grain size decreased from 1.32 μm to 0.32 μm with the increase of the reinforcing phase content, however, the strength has a significant enhancement, and the microhardness and compressive strength of the W-3%TiC-3%ZrC composites are 952.0 HV and 2754.6 MPa, respectively. In addition, the W-3%TiC-3%ZrC composites were also shown to exhibit sufficient thermal stability, with compressive strengths of 2716.2 MPa, 2560.8 MPa, and 2323.8 MPa at 200 °C, 400 °C, and 600 °C, respectively. The extremely high strength of W-matrix composites is due to the formation of various second phases in the composites. The appearance of the second phases plays a role in fine grain strengthening, dispersion strengthening, solid solution strengthening, and thermal mismatch strengthening.

Stress engineering of SiCf/SiC composites: Interfacial stress adjustment and its effects on tensile behaviors of UD SiCf/SiC composites fabricated by hybrid CVI and PIP methods

Internal stress is usually generated during the preparation of the SiCf/SiC composites and is generally considered to be uncontrollable and detrimental to SiCf/SiC composite's mechanical properties. However, in this study, internal stress is proposed for the first time as a tool to regulate the interfacial bonding properties of the SiCf/SiC composites. And the interfacial compressive stress was successfully controlled by hybrid CVI and PIP methods. The results of Raman analysis show that the interfacial compressive stress increases with the increase of the PIP SiC content. The interfacial shear strength (τi) and interfacial dynamic friction strength (τf) was determined by micro-shear tests. Both τi and τf increase with the increase of interfacial compressive stress. With different interfacial bonding strength, the SiCf/SiC composites show different tensile behaviors. A high τi can lead to a high tensile modulus and proportional limit stress (PLS) and a high τf can lead to the disappearance of the second linear stage and low fracture strain. The axial residual stress of matrix also was tested, and the results indicate that it does not have a dominant influence on the mechanical properties. Finally, the SiCf/SiC composites achieve the superhigh PLS of 729.8 ± 9.2 MPa and modulus of 288.0 ± 7.9 GPa when the BN thickness is 100 nm and the interfacial compressive stress is 1127.7 MPa. This strategy of interfacial stress engineering may provide a new and valuable design idea for improving the mechanical properties of the SiCf/SiC composite and other composites. This strategy is also of great significance for broadening the design criteria and enriching the preparation methods and internal stress regulation methods of high-performance composites.

Exploring thermal and in-situ mechanical properties of flexible 2D tungsten disulfide foam-polymer composite for thermal management

In the realm of thermal management applications, there is a growing need for flexible materials that can efficiently dissipate heat. Polymer composites incorporating two-dimensional (2D) materials offer promising solutions due to their superior thermal and mechanical properties. Tungsten disulfide (WS2) is an excellent filler candidate for polymer composites due to its superior thermal conductivity, mechanical strength, and electrical properties. Unlike graphene, WS2 has a tunable bandgap, exhibits higher thermal resistance in inert atmospheres, is an effective lubricant over a wide temperature range of −190°C to over 800°C, and offers superior gamma radiation shielding. However, high-density 2D material polymer composite fabrication faces challenges due to the agglomeration tendency and sedimentation of heavy nanomaterials within the polymer matrix. This poor dispersion stability negatively impacts the performance and reliability of the composite. We developed a flexible WS2 foam-polydimethylsiloxane (PDMS) composite via freeze drying and vacuum-assisted infiltration, which not only overcomes fabrication challenges but also enables unique filler reinforcement foam designs. The thermal conductivity of WS2-PDMS foam was 1.57 times higher than that of neat PDMS. These thermal properties were modeled using the Lewis-Nielsen model. In-situ tensile tests were conducted to understand the mechanical reinforcing behavior and failure mechanisms of WS2 foam, which were further studied using the Gibson and Ashby model. The addition of WS2 into PDMS resulted in an elastic modulus 1.56 times higher than that of neat PDMS. The composite's mechanical properties were analyzed using the Halpin-Tsai model. These findings highlight the potential of WS2-PDMS composites for flexible thermal management applications.

PENGARUH FRAKSI VOLUME DAN PEMBEBANAN TERHADAP SIFAT FISIK DAN MEKANIK KOMPOSIT BERPENGUAT SERBUK CANGKANG KERANG LOKAN

The increasing consumption of local clam shells which contain high nutritional value in society has resulted in an increase in waste sea shells in areas around the coast of Bengkulu Province. The high calcium content in lokan clam shells attracts researchers to study the physical and mechanical properties of epoxy resin composites reinforced lokan clam shell powder. This research aims to investigate the effect of variations in the volume fraction of lokan clam shell powder and the mold loading on the physical and mechanical properties of composites reinforced lokan clam shell powder. The process of manufacturing shell powder is carried out by heating at a temperature of 900oC for 6 hours. Variations in the volume fraction of lokan clam shell powder consist of 30, 50, 70%. Meanwhile, the mold loading was varied by 0, 500 N, and 1 kN. The manufacturing process uses hand lay-up techniques. Physical and mechanical tests on composites include water absorption tests, density, tensile tests and impact tests. The results of the research show that the powder volume fraction and mold loading influence the physical and mechanical properties of composites reinforced lokan clam shell powder. The best physical properties of composite were obtained at a powder volume fraction of 70% and a mold loading of 1 kN, namely with a density of 1.43 g/cm3. The best mechanical properties of composite were obtained at a volume fraction of 30% and a mold loading of 1 kN, namely with a tensile strength of 33.2 MPa and an impact toughness of 366.8 kJ/m2.