Applied Composite Materials最新文献

Herein, a coupled elastoplastic-damage analytical model is developed to analyze the effect of the plasticity of the resin on the failure behavior of 3D woven composites (3DWC). The proposed model is numerically simulated using different unit-cells of 3DWC and is verified by experimental data. The results show that under warp loading, the plasticity of the resin has a greater effect on component damage, and both the plasticity and the damage show an alternating iterative propagation mode; in contrast, under weft loading, the plasticity of the resin has a lesser effect on component damage, and both show an independent extension pattern. This work provides a guidance for the strength design of 3DWC structures such as aero-engine fan blades, which demonstrates significant engineering implications.

In recent years, laminated composites reinforced with natural fibers have extensively used in the various industries. One of the most important failure modes of laminated composite materials is translaminar fracture under different loading conditions. In this research, the effect of temperature on the translaminar critical strain energy release rate (CSERR) of the composites reinforced with cotton fibers was investigated. The cotton/epoxy samples were placed at different temperature conditions of 30, 0, and -30 °C. The translaminar CSERR values of cotton/epoxy laminated composites were obtained under pure mode I, mixed mode I/II with two different loading angles, and pure mode II loading conditions. To calculate the translaminar CSERR based on experimental results, numerical modeling was also performed. Besides, a modified version of Mixed Mode Fracture Envelope criterion was proposed to predict the mixed mode I/II translaminar fracture behavior of the cotton/epoxy laminated composites at the mentioned temperatures. The results showed that lowering the temperature has a great impact on the translaminar CSERR. It was also concluded that the change in the temperature had the greatest effect on the value of the mode I translaminar CSERR. Moreover, as the temperature decreased from 30 to 0 and -30 °C, the value of the mode I translaminar CSERR decreased around 80 and 90%, respectively.

This study focuses on the spring-back as a function of the degree of cure on single-curved metal-composite laminates. The manufacturing through a hot-pressing process involves different (curing) stages and can reduce the spring-back with the proper combination of forming and curing. The cure-dependent spring-back is measured and analysed as a function of material constituents, fibre directions, laminate layups, and the process parameters including temperature, holding time and pressure. The results demonstrate that the spring-back ratio after full-cured process is relatively small and mainly depends on the mechanical properties of the metal sheet in laminates. However, temperature and time have a significant effect on the spring-back of partially-cured laminates and the same type of fibre prepreg combined with two different metal sheets have similar trends of spring-back reduction. Moreover, the study found that the hybrid laminates with aluminium sheet delaminate at low pressure after full-cured, while the delamination disappears as the pressure increases. The characterisation on cure-dependency of the spring-back contributes to a better understanding of the deformability of the metal-composite laminates during the hot-pressing process and offers an opportunity to tune the spring-back of these laminates.

SiCp/Al composites are widely used in many important engineering applications due to their excellent material properties. High-volume fraction SiCp/Al composites are recognised as a typical difficult-to-machining material with significant brittleness, and negative rake angles are more suitable for cutting brittle materials. Ultrasonic elliptical vibration cutting (UEVC) has proven to be a specialised machining method that can improve the machinability of difficult-to-machining materials. Elucidating the influence of the negative rake angle on the dynamic properties of composites during UEVC is therefore particularly important. In this paper, the direction of the combined cutting force is considered separately for negative rake angle tools, as well as UEVC's unique transient cutting thickness, variable cutting angle, transient shear angle and characteristic of friction reversal, a UEVC cutting force model based on negative tool rake angle has been developed. And the deviation of the main cutting force between the experimental value and the theoretical value is less than 15% by systematic turning experiments, which verifies the accuracy of the model. Finally, the influence of different machining parameters on the cutting force is determined using the established model. The results show its effect on the cutting force is more significant when the cutting speed is less than 200 mm/s, other things being equal. In addition, the cutting force tends to decrease significantly as the depth of cut from 5 μm to 20 μm increases. However, the cutting force fluctuated less when the feed was increased. This work provides the benchmark for negative rake angle cutting of SiCp/Al.

SiCp/A356 brake discs experience cyclic thermal loading during service, leading to a certain degree of mechanical deterioration in the brake disc material (SiCp/A356 composites), thereby reducing the thermal fatigue resistance of the brake disc, ultimately threatening the braking safety of urban rail trains. To investigate the mechanical deterioration patterns and mechanisms of the SiCp/A356 composites, thermal cycling experiments were conducted, along with simulation methods and microstructural analysis. The results indicate that the upper temperature limit of thermal cycling determines the microstructural damage modes and degree in SiCp/A356 composites, and the damage degree is positively correlated with mechanical deterioration. A temperature of 200 °C is identified as suitable for long-term service of SiCp/A356 composites. Thermal cycling induces thermal mismatch stress and residual stress within the material, serving as the primary driving forces for microstructural damage. Thermal cycling reduces the dislocation density in the near-interface (Al-SiC interface) matrix, improving the material's ductility. However, dislocation accumulation in the matrix far from the interface results in stress concentration, promoting matrix damage and crack formation, thereby compromising mechanical properties. The sole strengthening phase, Mg₂Si, is susceptible to aggregation and coarsening, leading to reduced mechanical properties after peak aging. The principal cause of interface crack is the stress concentration caused by dislocation accumulation, ultimately leading to interface failure. This research provides important guidance for the operation and maintenance of SiCp/A356 brake disc.

This study investigated the effectiveness of 3D woven structural composite-based aircrew helmets comprising a 3D woven solid shell and a 3D woven honeycomb liner. This research adopted a structured sequence of steps to integrate desired aircrew helmet properties. The study involved the analysis of 3D woven structural composites through quasistatic compression and dynamic impact tests to assess their compressive strength and impact energy properties, respectively. Initially, the study focuses on optimizing the honeycomb liner by adjusting its structural parameters to improve the compressive strength. The research then delved into the critical role of impact energy, aiming to enhance load transfer to the liner for maximal impact energy absorption. Key findings highlight that the L2T2H3 honeycomb liner configuration, when combined with the OR8L3M shell, significantly improves the protective performance by exhibiting superior impact energy, cushioning properties, and compressive strength. Factors such as weave architecture, impactor geometry, impactor velocity, and face sheet thickness were found to influence the energy absorption capacity, emphasizing the importance of structural design optimization. The combined use of helmet shell and liner components demonstrated superior energy absorption capabilities compared to individual components. This combination suggests a successful approach for achieving enhanced performance in aircrew helmets. By analyzing compressive strength and impact energy, this research contributes to the ongoing efforts to enhance the performance of aircrew helmets, thereby ensuring improved safety and protection for aircrew members operating in high-risk environments.

Carbon-Kevlar hybrid woven reinforcement materials have high specific strength and modulus, excellent fatigue resistance, which are widely used in aerospace applications. Due to its special mechanical properties by hybridization, the forming quality is affected by various factors such as reinforcement properties and process parameters. In order to improve the forming quality of Carbon-Kevlar hybrid woven reinforcement and reduce the forming defects, this paper proposes a new optimization method combined with genetic algorithm. Taking the maximum shear angle of the preform as the optimization objective, a genetic algorithm is used to optimize the load and size of the tetrahedral structure blank holder. The results indicate that the peak shear angle decreased from 52.14° to 43.90°, while the optimal forces on the five parts of the blank holder are RF₁ = 20 N, RF₂ = 26 N, RF₃ = 45 N, RF₄ = 14 N, RF₅ = 45 N, respectively, and the optimal gaps between the blank holder parts is BW₁ = 4 mm, BW₂ = 22 mm. Then, potential wrinkling areas were predicted by the in-plane negative strain. It was found that the minimum in-plane negative strain of the sample in the two main fiber directions was effectively controlled, and the negative strain distribution in the useful areas was more uniform, thereby reducing the potential wrinkling areas, indicating the effectiveness of the optimization method.

The sensitivity of carbon fiber composite laminate to impact damage makes impact damage a significant cause of composite material performance degradation. This study aims to investigate the influence of surface glass fibers on carbon fiber composite laminates under low-velocity impact. A user-defined VUMAT subroutine based on the Puck criterion was employed to implement an intralaminar damage model, while a bilinear cohesive model based on quadratic criterion in Abaqus was used to simulate interlaminar damage. By simulating the low-velocity impact behavior of carbon fiber laminates under three energy levels (2 J, 4 J, and 8 J), the predicted mechanical response results were compared with the experimental results from the literature to validate the rationality of the model. The mechanical response and damage evolution under impact loading were studied by adding glass fibers of different angles and thicknesses on the surface layer of carbon fiber laminate. The results show that increasing the thickness of surface glass fibers can effectively enhance the impact resistance of carbon fiber composite laminates, and a single layer glass fibers at 90° provides better protection than at 45°. The results of this study are instructive for the selection of the thickness as well as the angle of the glass fibers on the surface of carbon fiber composite laminates.

This study investigated the mechanical behaviour of glass fibre epoxy composites with and without an embedded polyethylene terephthalate (PET) substrate used for printed electronic applications, with the mechanical behaviour integrity studied under different loading modes: three-point bending, tensile, and short-beam stress (SBS) tests. The main objective of this study was to investigate the influence of the substrate location within the laminate. Fracture profiles were observed by visual inspection during the mechanical tests and scanning electron microscopy (SEM) after failure to identify differences in the damage mechanisms and their propagation. Tensile tests indicated that embedding the PET substrate did not affect the ultimate strength of the laminate, while the bending and SBS tests indicated that the substrate integration reduced the bending strength and ILSS by 10% and 50%, respectively, depending on the substrate location.

This paper is a continuation study of the residual compressive strength of composite laminates after impact under hygrothermal conditions. Two carbon fibre/epoxy plywood specimens with different lay-ups ([45/-45/0/0/45/0/0/0/90/-45/0]s and [45/-45/0/90/0 /0/0/0/90/0/-45/45]s) were investigated, The materials were subjected to 500 h, 1000 h and 2000 h of service time in a climatic chamber at a temperature of 60 °C and 100% relative humidity, followed by low-velocity post-impact compression using an energy level of 15 J. Experimental and numerical simulations are used to study the residual compressive strength and damage extension of the material. Using the ultrasonic C-scan technique, the internal damage of the specimens was scanned, and the damage evolution in impact and compression tests was analysed. Damage evolution in impact and compression tests was investigated using ultrasonic C-scanning to scan the internal damage of the specimens. The strain change maps of the specimens during compression are studied using the Digital Imaging (DIC) technique. Vumat subroutine coded in Fortran and used in commercial software (ABAQUS) for numerical simulation. To study the effect of damage extension of materials on post-impact and post-impact compression for different hygrothermal times. It was found that the residual compressive strength depended on factors such as the material's hygrothermal time and the initial defects in the plywood; that the 90° and ± 45° fibre orientations played a positive role in the material's hygrothermal; that the hygrothermal made the material's damage more catastrophic; and that the buckling of hygrothermal specimens was not only at the impact position, but was also reflected at the edges. In CAI testing, it was found that the hygrothermally treated specimens were damaged similarly to the desiccation treated specimens, but that compression resulted in a flexural position affected by hygrothermal, which determined the material CAI strength.