Applied Composite Materials最新文献

This paper aims to investigate the tensile creep behavior of PVC flexible composites reinforced with various aramid warp-knitted fabrics (PCRAWF). The tensile creep test of PCRAWF was conducted and the impact of various tissue structure reinforcements on the viscoelastic behavior of PCRAWF was also discussed. Dynamic mechanical analysis (DMA) tests were conducted on PCRAWF to explore the effect of temperature on the creep strain and creep recovery properties of PCRAWF. The variation in viscoelastic properties of PCRAWF with temperature was analyzed. The decomposition behavior of aramid fibers and PVC resins in a nitrogen (N₂) atmosphere was analyzed using thermogravimetric analysis (TGA). The experimental results showed that as the density of the reinforcing fabric increases, the creep strain of the corresponding PCRAWF decreases. The amount of creep strain increases as the loading force increases, and the rate of increase gradually decreases. The creep strain of PCRAWF increases as the temperature rises, and the creep recovery decreases with increasing temperature. The creep strain increases by approximately 0.4–1.6% as the temperature rises from 30 °C to 60 °C, and by about 0.2–0.6% as the temperature increases from 60 °C to 90 °C. The TGA results analyzed the thermal degradation temperatures of aramid fiber and PVC composites in N₂ to reach 680 °C and 480 °C, respectively. The characterization of tensile creep behavior has significant potential for predicting the long-term performance of fabric-reinforced polyvinyl chloride flexible composites. Based on the experimental results of the creep of PCRAWF, the constitutive Kelvin-Maxwell model was used to establish the constitutive equations with the experimental data for numerical simulation.

This work proposes a novel solution for manufacturing hybrid metal-composite joints, in which different pin shapes are evaluated for their capability to penetrate long carbon fiber epoxy composites successfully and for the mechanical behavior determined by each configuration. On the metal side, pins are manufactured by Laser Powder Bed Fusion (LPBF), downsizing the currently adopted solutions and, at the same time, developing new blocking features aimed at enhancing the mechanical properties of the joint. The different configurations were evaluated in two distinct experiments: the first to evaluate the induced defects in the composite substrate and the second to characterize the mechanical behavior of the joint. It emerges that smaller pins produce much less damage and misalignments in the composite structure with respect to the conventional pin solution, whereas the new “blocking features” configurations consistently increase maximum pullout load and energy with respect to the conventional pin solution, with the same level of fiber damage.

The present paper investigates the low-velocity impact behaviour of carbon-fibre reinforced-plastic (CFRP) composite panels and the damage incurred when they are subjected to a single impact. The relationship between the depth of permanent surface indentation that results and the associated area of interlaminar delamination damage is investigated for two different thicknesses of composite panels. In particular, the delamination damage area increases with impact energy for both thicknesses of composite panel that were studied. Likewise, the indentation depth also increases with increasing impact energy, again for both thicknesses of CFRP panels. It is shown that the indentation depth, at the centre of the indentation, may be used to provide an indication of the extent of delamination damage within the CFRP panel after impact. Indeed, from plotting the indentation depth versus the interlaminar delamination normalised by the thickness of the panel area there is shown to be a unique ‘master’ relationship, with a positive intercept indicating that the indentation damage seems to result before delamination damage initiates. Thus, for both thicknesses of CFRP panels, it is suggested that the indentation process is a precursor to interlaminar delamination damage.

Abstract

Carbon fiber composite can be a potential candidate for replacing metal-based battery enclosures of current electric vehicles (E.V.s) owing to its better strength-to-weight ratio and corrosion resistance. However, the strength of carbon fiber-based structures depends on several parameters that should be carefully chosen. In this work, we implemented high throughput finite element analysis (FEA) based thermoforming simulation to virtually manufacture the battery enclosure using different design and processing parameters. Subsequently, we performed virtual crash simulations to mimic a side pole crash to evaluate the crashworthiness of the battery enclosures. This high throughput crash simulation dataset was utilized to build predictive models to understand the crashworthiness of an unknown set. Our machine learning (ML) models showed excellent performance (R² > 0.97) in predicting the crashworthiness metrics, i.e., crush load efficiency, absorbed energy, intrusion, and maximum deceleration during a crash. We believe that this FEA-ML work framework will be helpful in down select process parameters for carbon fiber-based component design and can be transferrable to other manufacturing technologies.

This paper establishes a composite material damage analysis strategy that retains the hygrothermal state to investigate the damage behavior and mechanical performance characteristics of composite materials in hygrothermal environments. Initially, mass diffusion and heat conduction are equivalently considered, and a hygrothermal state predefined model is developed using a combination of sequential and fully coupled approaches. Then the hygrothermal stress field is extracted as the initial state of the compression process, and a compression progressive damage analysis is conducted using the VUMAT subroutine. Additionally, the accelerated hygrothermal aging experiments are conducted to investigate moisture absorption behavior and moisture diffusion coefficients. Then the quasi-static compression tests are carried out on the specimens before and after aging, with failure processes recorded using Digital Image Correlation (DIC). Experimental and simulation results reveal that hygrothermal conditions lead to matrix cracking and debonding from the fiber surface, generating an uneven stress field internally. This results in earlier occurrence and increased severity of delamination during the compression process. The dominant failure modes include wedge splitting and longitudinal cracking. The compressive strength, failure strain, and elastic modulus of the specimens decrease after aging. The analysis strategy developed in this paper effectively reflects the hygrothermal state during compression, aligning more closely with the actual physical processes.

Abstract

This paper experimentally and numerically investigates the failure behavior of plain woven composite-metal connection structures (T-joints) under loads in different directions. According to the direction of load application, it can be divided into TX specimens and TZ specimens. Wherein, TX and TZ are subjected to the tensile load parallel and perpendicular to the composite panel, respectively. Test results show significant differences in the ultimate load, failure modes and strain distribution among different specimens. Increasing the contact area between the lower block and the composite panel and adding round to the contact part between the metal part and the composite panel can improve the load-carrying capacity of the T-joints. The multiscale simulation is conducted to study the failure process of T-joints. Micro-scale and meso-scale models are established to obtain the mechanical properties of the plain woven composite, and the error between the simulated results and the experimental data is less than 10%. Progressive damage analysis is then done by using the macro-scale model. The simulated failure load and damage process of T-joints are consistent with the test results. The information and proposed multiscale analysis method on the failure behavior of T-joints are useful for the optimal design of similar structures.

The metal-matrix composites (MMCs) with biomimetic bricks-and-mortar architectures have been experimentally demonstrated to exhibit excellent strength-ductility match. Here, biomimetic bricks-and-mortar architecture mimicking masonry bonds was introduced in numerical models. By translating perpendicular layers on stack bond model, 1/2 running and running bond models were established. The results reveal that elongation of running bond model is the highest (4.77%), which is ∼ 1.5 times as that of stack type model. The strength of these models is similar (330 ± 1 MPa). However, it is the trade-off between load bearing capacity and fracture of SiC particles. In the stack bond model, over a small junction layer area led to a relatively straight crack path and thus lower elongation. On the contrary, running bond model shows a zigzag main crack. So, the main crack deflects frequently with high energy consumption. Furthermore, crack deflection into matrix cell increases propagation resistance, leading to the highest elongation in the running bond model. Therefore, the biomimetic bricks-and-mortar architecture delays and deflects main crack propagation. These findings have significant implication for the architecture design of advanced composite materials.

Abstract

This paper describes design, manufacture, and testing of a linerless composite vessel for liquid hydrogen, having 0.3 m diameter and 0.9 m length. The vessel consists of a composite cylinder manufactured by wet filament winding of thin-ply composite bands, bonded to titanium end caps produced by additive manufacturing. The aim was to demonstrate the linerless design concept with a thin-ply composite for the cylinder. The investigation is limited to the internal pressure vessel, while real cryogenic tanks also involve an outer vessel containing vacuum for thermal insulation. Thermal stresses dominate during normal operation (4 bar) and the layup was selected for equal hoop strains in the composite cylinder and end caps during filling with liquid hydrogen. Two vessels were tested in 20 cycles, by filling and emptying with liquid nitrogen to 4 bar, without signs of damage or leakage. Subsequently, one vessel was tested until burst at almost 30 bar.

Fibre kinking is the most prevalent failure mode observed in UD composites. The accurate prediction of kinking failure is of paramount importance in industrial applications. To address this challenge, we develop a non-linear mean-field debonding model (NMFDM) based on our previous work, which efficiently captures the non-linear material behaviour of UD composites under longitudinal compression leading to kinking failure. Building upon the foundation of our earlier mean-field model, this enhanced NMFDM incorporates geometric non-linearity due to fibre rotation under longitudinal compression and the non-linear elasticity of fibres in the fibre direction. These additions address crucial aspects in kink band formation and the typically non-linear elastic behaviour of carbon fibres, which were not considered in our previous work. Additionally, we introduce a fibre kinking model (FKM) to predefine initial fibre misalignments in the geometries, allowing us to study the formation of kink bands. The FKM considers the effects of initial misalignments and fibre rotations during kinking by proposing a transformation law for off-axis cases. As a representative example, we investigate the initiation and evolution of kink band formation in an AS4/8552 UD composite by predefining various initial misalignments. The results demonstrate that our newly proposed NMFDM yields reliable predictions of kink band formation in UD composites, outperforming other existing models and even comparing favorably to micrograph observations of kink bands. Compared to our previous work, this enhanced model offers a more comprehensive understanding of kink band formation, particularly under large strains, by incorporating the non-linear elasticity of fibres in the fibre direction. This advancement opens up potential applications in designing composite structures with improved resistance to compressive failure, paving the way for broader applications in aerospace, automotive, and other industries where high-performance composite components are crucial.