Applied Composite Materials最新文献

Carbon fiber reinforced polymer (CFRP) is widely used in aerospace due to its excellent mechanical properties, and the corresponding high-efficiency, high-strength joining techniques have become a key research focus. Among various factors influencing the failure mechanisms and residual life of CFRP joints, the actual service environment plays a crucial role. In this study, the damage formation and performance degradation of CFRP bolted joints under thermo-oxidative aging condition were investigated. Experimental results demonstrate that, even in the absence of external loads, a thermo-oxidative environment can lead to material internal damage within the jointed zone. The difference in the coefficients of thermal expansion between the fibers and matrix can also lead to the appearance of matrix damage and delamination at the entrance and exit of the joining holes. In addition, From the experimental results, it can be seen that thermo-oxidative ageing has a significant effect on the tensile load-bearing properties of the joining structure, and with the increase in ageing temperature up to 150℃, the load-bearing stiffness and strength of the joining structure decreases by up to 34.8% and 23.1%, respectively. These findings highlight the impact of thermo-oxidative aging on the integrity and performance of CFRP bolted joints, emphasizing the need to account for environmental degradation in the design and durability assessment of aerospace composite structures.

This study addresses the challenge of optimizing mechanical performance in aramid/carbon fiber hybrid-reinforced polymer (A/CFHRP) composites by investigating effects of hybrid ratio. Specimens with controlled aramid/carbon fiber ratios were fabricated via vacuum-assisted resin transfer molding (VARTM). The novelty lies in the integration of high-resolution in situ X-ray computed tomography (CT) tensile testing with three-dimensional (3D) damage analysis, enabling visualization of failure mechanisms under progressive loading. 3D reconstructions revealed intralaminar damage distribution patterns and crack propagation pathways. Low aramid content (26.7 wt%) exhibited brittle carbon fiber-dominated fracture with limited crack deflection. Excess aramid (80 wt%) induced ductile pull-out mechanisms but compromised strength. Additionally, in situ CT images show that carbon-aramid hybridization can improve stress transfer and energy dissipation. This study offers a key theoretical foundation for enhancing the performance of A/CFHRP composites and also broadens the application scope of in situ CT technology.

This study presents a comprehensive comparative analysis of tribological and thermal properties of PA-based composites, investigating PA66 reinforced with short glass fibers containing PTFE/silicone versus PA6 reinforced with glass beads in gear pairings. Durability lifetime tests were performed to analyze the tribological behavior of steel pinion and driven composite gear systems under controlled torque conditions at high, medium, and low loadings at room temperature to investigate load-failure mechanism correlations. DSC measurements were performed to research how glass transition temperature (T_g) and different crystallization behaviors impact lifetime performance. Abrasive wear on gear flanks was measured to evaluate the impact of glass reinforcements on friction properties. Thermal feedback regarding gear operation was obtained through infrared camera measurements of gear surface temperatures. Results demonstrate that thermal monitoring reveals temperature spikes exceeding 20 °C precede failure, with PA6 reinforced with glass beads exhibiting thermal runaway at high torques while PA66 with glass fibers and PTFE/silicone maintains steady-state thermal profiles. PA6 with glass beads demonstrates superior low-torque performance through isotropic reinforcement, whereas PA66 with glass fibers and PTFE/silicone provides consistent high-torque reliability via internal lubrication mechanisms.

This study investigates the damage effects and residual structural strength of Carbon Fiber Reinforced Polymer (CFRP) laminates under multi-factor coupled lightning strikes, combining numerical simulations and experimental methods. An electro-thermal-chemical coupling model was developed to simulate lightning damage under varying layup angles, lightning current peaks (7.6–100 kA), different thickness and grounding conditions. Experimental validation was conducted via a lightning current A-component generator and residual tensile strength tests. The results show that the damage area is directly proportional to the current size, showing rapid expansion at the peak value. When the current peak reaches 46 kA, the damage area reaches 2738.4 mm². The single ground will lead to the asymmetric damage of carbon fiber laminates, and the damage on the grounding side will increase by 53.5%, but the total area is similar to the two-side ground. The residual tensile strength of carbon fiber laminates decreased significantly with the increase of current. At the peak of 45 kA current, the residual tensile strength decreased by 39%. The simulation accurately predicted damage areas, aligning with experimental results. The linear fitting was performed on the residual intensity data with different current amplitudes, and the fitting index R² > 0.9. This article analyzes the correlation between conductive paths and damage characteristics, providing research references for optimizing lightning protection design.

In this paper, a finite element model based on continuum damage mechanics was developed to investigate the load transfer and damage progression mechanisms of ply-interleaved composite laminates subjected to tensile loading. Hashin criterion and a gradual degradation scheme were used to predict the intralaminar damage initiation and evolution, which were coded and integrated into the commercial finite element package ABAQUS/Explicit through a user-defined VUMAT material subroutine. Synchronously, an interface cohesive element was utilized to predict the interlaminar delamination damage. To verify the proposed model, quasi-static tensile tests were performed on specimens with different interruption distances. The results showed that with the increasing interruption distance, the failure load, failure displacement, and stiffness of the specimens decrease. A good agreement was achieved between the experimental and simulation results in terms of load-displacement response and damage morphology, validating the predictive capability of the model. Furthermore, the load transfer mechanism and damage evolution process of ply-interleaving composite laminates under tensile loading were clearly revealed. This work will pave the way for the engineering application of ply-interleaving composite structures.

This study investigates the flexural and shearing performance of a fully recyclable matrix system used to generate a sustainable composite (basalt fiber-reinforced Recyclamine®). It also compares the composite’s mechanical performance against its close counterpart, basalt-epoxy, manufactured with a commonly used room-cured epoxy system. The mechanical performance of both systems is evaluated, with void content monitored as an influential processing parameter. The composites were prepared using the vacuum-assisted resin transfer molding (VARTM) process, and void content analysis showed marginally higher void content in basalt-Recyclamine (4.9%) than in basalt-epoxy (4.4%). The void content was above the optimum values of 1-2% but within acceptable ranges for vacuum-assisted fabrication processes. Experimental characterization included flexural testing and shear testing as per ASTM standards. The results showed that although basalt-Recyclamine exhibited 14.1% lower flexural strength than basalt-epoxy, its flexural modulus was 10.7% higher. Furthermore, the shear strength of basalt-Recyclamine was superior to that of its counterpart by 18.4%, but its shear modulus was 8.5% lower. Microscopic examination showed different failure mechanisms for the two systems, with basalt-Recyclamine undergoing more progressive failure modes. The findings of this study indicate that basalt-Recyclamine composites can offer comparable mechanical performance to conventional epoxy systems, thus facilitating a pathway toward greener future applications of composite materials.

Graphical Abstract

The function of single-phase and multi-phase shear thickening fluids (STFs) in body armor applications has been extensively studied. However, boron carbide (B₄C), one of the toughest particles, has not been sufficiently investigated for its quasi-static role and low-speed dynamic impact with STF. In this study, multiphase STFs were formulated by incorporating B₄C particles with three different size ranges (1–3 μm, 22–59 μm, and 125 μm) into a silica–PEG200-based STF containing 55 wt% silica, at reinforcement concentrations of 5%, 10%, and 20% by weight. These STFs were then impregnated into p-aramid fabrics to fabricate composite samples, which were subjected to low-velocity dynamic impact tests (using a drop tower system according to ASTM D7136) and quasi-static stab tests (using a universal testing machine). The effects of B₄C reinforcement content and particle size on the mechanical performance of the STF-treated fabrics were systematically investigated. Based on the test results, the research determines a critical reinforcement threshold of 10%. Beyond this level, excessive B₄C disrupts the thickening mechanism of the STF and reduces impact strength. The study shows that increasing B₄C particle size improves resistance, particularly in dynamic impact scenarios, but has a limited effect in quasi-static tests due to reduced contact area. The results provide important insights for optimizing STF-reinforced composites for protective applications, balancing material hardness, particle distribution, and STF rheology to maximize performance.

This study investigates the influence of joining parameters on the dynamic tensile performance of hybrid bonded-bolted GFRP/Al joints, which are crucial in aerospace and automotive applications due to their high strength and lightweight properties. The motivation lies in addressing challenges related to geometric imperfections and varying assembly conditions that significantly impact joint reliability under dynamic loads. Experiments and numerical simulations were conducted to evaluate the effects of perpendicularity errors, fit clearance, and preload on the mechanical performance and failure modes of these joints. Dynamic tensile tests were performed using controlled loading conditions, and finite element modeling was employed to validate experimental findings and provide additional insights into stress distributions and failure mechanisms. The results demonstrated that perpendicularity errors significantly degrade joint performance. Specifically, joints with a 3° perpendicularity error parallel to the load direction exhibited a 64.40% reduction in energy absorption, whereas errors perpendicular to the load direction resulted in a 31.09% reduction. Excessive fit clearance changed the failure mode from tensile to shear, particularly at lower loading speeds. Increasing the preload effectively delayed adhesive layer delamination, reduced deformation, and enhanced overall joint strength. This research provides novel insights into the effects of geometric errors and assembly conditions on hybrid joint performance.

In the fabrication of three-dimensional textile composites, needle-punching technology establishes initial interlaminar bonding through the introduction of Z-directional fibers. However, the Limited connection strength formed by this process constrains the optimization of the overall mechanical properties of preforms. To address this Limitation and enhance both interlaminar and in-plane mechanical performance of the reinforcement, this study integrates stitching technology with needle-punching, developing a 3D needled and stitched integrated process. To better understand how needling density and stitching density affect the tensile properties of three-dimensional needled and stitched preforms (3D-N&SPs) and ceramic matrix composites, five groups of preforms and composites were designed and manufactured with varying processing parameters. To this end, we employ in-plane tensile testing alongside in-situ computerized tomography (CT) scans to thoroughly examine the mechanical responses and damage evolution patterns in these materials. The findings reveal that at a needling density of 35 pins/cm², the sample designated as P3, which features the highest stitching density, achieves a peak tensile strength of 26.8 MPa. This improvement is primarily attributed to enhanced load transfer paths facilitated by the stitch threads. In contrast, within the needling density range of 30–35 pins/cm², Sample P4, which has a lower needling density, reaches a peak tensile strength of 21.11 MPa. This performance advantage is essentially Linked to reduced fiber damage during processing. However, increasing both needling and stitching densities results in reduced tensile strength of composites. Consequently, reductions in tensile strength are observed, ranging from 8.1 to 9.0% for needling density and from 4.4 to 9.1% for stitching density. The performed CT analysis also indicates that the primary failure mechanism involved crack propagation along the axial direction of the Z-oriented needled fiber bundles, while the presence of pore defects exacerbates damage progression in the composite system.