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Due to the effects of manufacturing process, there are lots of distributed voids in the interior area of three‐dimensional (3D) woven C/SiC composites, leading to the difficulties in predictions of damage evolution and ultimate strength. In this work, the mesoscale geometry of 3D woven C/SiC composites is reconstructed based on the high‐resolution CT scanning, considering the yarn path, yarn profile, and void content. The CT‐based reconstructed model agrees well with the experimental observations. Then, the constitutive laws of mesoscale constituents and macroscale structure are established and implemented numerically by the user‐defined material subroutine UMAT. Finally, the established constitutive laws are applied for the reconstructed model, and the mesoscale and macroscale nonlinear progressive damage behavior of 3D woven C/SiC composite structures are predicted using the hierarchical multiscale method, which are also validated by the experiments. The established CT‐based multiscale computational scheme would be a potential tool for performance evaluation and design of composites. [ABSTRACT FROM AUTHOR]

• The multiscale scheme incorporates the strain rate effect in composites. • The microscale RVE accurately captures the off-axis damage process in composites. • Shear enhancement greatly affects the dynamic behavior of 3D braided composites. In this paper, a dynamic multiscale model is proposed for three-dimensional four-directional (3D4D) braided composites, considering the effects of strain rate and shear enhanced failure mechanism. The strain rate-dependent constitutive models are established for both resin and yarns. The accuracy of the yarn model is validated by comparing the simulated stress-strain curves with the experimental results obtained from the Split Hopkinson Pressure Bar (SHPB) tests with various strain rates. The shear enhancement coefficient of the yarn is determined from the failure envelopes with a discussion of crack propagation angles. The results show that, based on the calculated microscale properties, the mesoscale model accurately predicts both the longitudinal and transverse compressive strain-stress behavior of 3D4D braided composites at different strain rates. A comparative analysis reveals that the shear-enhanced failure model achieves a better prediction compared with other counterparts, such as Hashin-Rotem and Tsai-Wu Models. The proposed dynamic multiscale scheme for 3D braided composites is an efficient and accurate tool to characterize their multiscale features and strain rate-dependent behavior. [ABSTRACT FROM AUTHOR]

The existing fast concurrency algorithms are difficult to predict the dynamic mechanical performance of three-dimensional (3D) braided composites from different scales. A modified Finite Element Method Cluster Analysis (FCA) method is employed to address this challenge. The modified FCA method is consisted of an offline and an online stage. In the offline stage, the high-fidelity Representative Unit Cell (RUC) is compressed to form a cluster-based RUC via the k -means method. Additionally, the cluster interaction matrix is calculated. In the online stage, the cluster interaction matrix is updated according to the strain rate levels for predicting the stress–strain curves for the RUC. Based upon the comparison with the data obtained from the Split Hopkinson Pressure Bar (SHPB) experiments, it is found that the modified FCA method can accurately predict the stress–strain curves under different strain rates for RUCs. Additionally, the modified FCA method provides a great improvement on computing efficiency when predicting the dynamic behavior of 3D braided composites. [ABSTRACT FROM AUTHOR]

The effective properties of lithium-ion battery (LIB) cathode are determined by both the volume fractions of constituents and the morphological features of microstructure. However, it is difficult to establish an accurate quantitative relationship between the macroscopic effective properties and microstructural features. Deep learning techniques, due to their exceptional nonlinear fitting capabilities, have been widely applied in various complex fields. Our study presents a generation scheme of numerous three-dimensional (3D) digital microstructures of cathode, using a deep convolutional neural network (CNN)-based stochastic reconstruction algorithm combining with the scanning electron microscope (SEM) images. The reconstructed samples are substituted with the corresponding finite element (FE) models, and the effective mechanical and electrochemical properties are assessed through the FE-based homogenization theory. Finally, the generated cathode samples and their effective properties are used to train the 3D CNN for performance prediction. This study demonstrates that the deep learning approaches can accurately and rapidly reconstruct the microstructure of cathode and predict their effective properties. Furthermore, the established framework can be extended to other heterogeneous materials. • Cathode microstructure feature extraction based on transfer learning is proposed. • A CNN-based stochastic reconstruction method for microstructures is developed. • CNN and homogenization theory are used for properties prediction of microstructures. [ABSTRACT FROM AUTHOR]

Abstract A multiscale elasto-plastic damage model is developed to predict the nonlinear behavior of three-dimensional (3D) braided composites. In this model, the sequential multiscale method is applied to transfer the effective properties from microscale to mesoscale, and from mesoscale to macroscale. The constituents at the microscale consist of fiber, matrix and interface which are consistent with the mesoscale ones. The fiber is considered to be elastic and brittle, and the elastic damage model is applied to degrade the stiffness. For the epoxy matrix, a coupled elasto-plastic damage model is proposed to integrate the effects of plasticity and damage, and furthermore the paraboloidal yield criterion is adopted to characterize the different types of mechanical behavior in tension and compression. The bilinear constitutive relation based on the cohesive element is used to investigate the properties of interface. A user-defined material subroutine (UMAT) in the nonlinear finite element analysis software ABAQUS is written to implement the proposed model and determine the response for 3D braided composites under quasi-static tension. The numerical simulations are compared with the corresponding experiments and the results show that they agree well with each other. [ABSTRACT FROM AUTHOR]

A coupled elastic-plastic damage model is developed to describe the non-linear mechanical behavior of three-dimensional (3D) braided composites. In this model, the fiber breakage, inter-fiber fracture and matrix fracture are considered in the level of the fiber bundle and matrix. The onset and propagation of fiber bundle failure mechanisms are elastic and brittle, which is accounted for elastic damage model, and the elastic-plastic damage model used to describe the degradation of matrix is non-linear with progressive damage and inelastic strains. A set of internal variables are introduced to characterize the damage states of the fiber bundle and matrix and as a subsequence the degradation of the material stiffness. The damage initiation and propagation criteria are based on the Hashin criteria for the fiber bundle and the von Mises yield criterion for the matrix. The proposed damage model is implemented in the non-linear finite element analysis code ABAQUS using a user-subroutine UMAT to determine the response behavior of 3D braided composites under quasi-static loading, and the numerical predictions are compared with experimental data. The results predicted by the proposed model agree well with the experiment. [ABSTRACT FROM AUTHOR]

Virtual testing is a powerful tool to characterize the mechanical behavior of materials owing to its excellent predictive ability. However, virtual testing for composite structures remains challenging due to their natural multiscale heterogeneities and expensive computational costs across scales. This paper proposes a FE-SCA concurrent multiscale framework to solve this challenge, where FE and SCA represent the finite element method and the self-consistent clustering analysis, respectively. The mechanical behavior of three woven structures, including open-hole plate, Isoipescu shear, and biaxial tensile specimens, are predicted using the proposed method. The results show that the established FE-SCA concurrent multiscale framework can virtually characterize the damage initiation and evolution for both macroscale woven structures and mesoscale woven representative volume elements. Moreover, it shows significantly higher efficiency compared with the traditional FE2 framework. Due to the high efficiency and predictive ability, the FE-SCA concurrent multiscale virtual testing has the potential to be a pathway toward composites design and structure optimization. [ABSTRACT FROM AUTHOR]

A meso-mechanical computational model based on the finite element method (FEM) is developed to predict the progressive elastic-plastic damage and failure behavior of three-dimensional four directional (3D4D) braided composites under multiaxial loadings. Firstly, the constitutive laws for mesoscale constituents (i.e. yarn, matrix and interface) of braided representative volume element (RVE) are established and implemented by the user defined material subroutine UMAT in ABAQUS. Then, how to build the braided RVE and conduct the simulation are introduced. After that, the uniaxial tensile data is used to verify the proposed model. Finally, the damage and failure behavior of the RVE under multiaxial loadings is investigated, considering the effects of loading paths and interface. The results show that loading path and interface have little effect on the strengths. The predicted failure envelopes in different stress spaces for RVE are compared with the Tsai-Wu and Hoffman theories, which are much closer to the Tsai-Wu theory. [ABSTRACT FROM AUTHOR]

Rubber composites are hyperelastic materials with obvious stress-softening effects during the cyclic loading–unloading process. In previous studies, it is hard to obtain the stress responses of rubber composites at arbitrary loading–unloading orders directly. In this paper, a hyper-pseudoelastic model is developed to characterize the cyclic stress-softening effect of rubber composites with a fixed stretch amplitude at arbitrary loading–unloading order. The theoretical relationship between strain energy function and cyclic loading–unloading order is correlated by the hyper-pseudoelastic model directly. Initially, the basic laws of the cyclic stress-softening effect of rubber composites are revealed based on the cyclic loading–unloading experiments. Then, a theoretical relationship between the strain energy evolution function and loading–unloading order, as well as the pseudoelastic theory, is developed. Additionally, the basic constraints that the strain energy evolution function must satisfy in the presence or absence of residual deformation effect are derived. Finally, the calibration process of material parameters in the hyper-pseudoelastic model is also presented. The validity of the hyper-pseudoelastic model is demonstrated via the comparisons to experimental data of rubber composites with different filler contents. This paper presents a theoretical model for characterizing the stress-softening effect of rubber composites during the cyclic loading–unloading process. The proposed theoretical model can accurately predict the evolution of the mechanical behavior of rubber composites with the number of loading–unloading cycles, which provides scientific guidance for predicting the durability properties and analyzing the fatigue performance of rubber composites. [ABSTRACT FROM AUTHOR]

An efficient and accurate multiscale modeling for the mechanical behavior of braided composites with complex microstructure is an outstanding challenge in the mechanics of composite materials. In this work, a concurrent three-scale scheme FE-SCA2 is proposed for predicting the macroscopic nonlinear behavior of braided composites associated with the microscopic plastic and damage of the constituents, where FE and SCA are short for finite element method and self-consistent clustering analysis, respectively. In this concurrent scheme, the macroscale behavior of the braided composites is handled by FE analysis, and the microscale and mesoscale behavior of the constituents are handled by SCA simultaneously with the data-driven clustering discretization. To demonstrate the accuracy and efficiency of the proposed scheme, we first predict the asymmetric anisotropic yield and failure surfaces for braided composites and then analyze the nonlinear behavior of a braided composite plate under bending. The computational results are compared with FE method results and experimental data from the literature, with good agreement in cases where such data is available. It is shown that the microscale, mesoscale, and macroscale nonlinear behavior of braided composites can be captured simultaneously using the proposed FE-SCA2, which would be difficult to be characterized by experimental methods. The proposed multiscale method could be applied for composite structures with various properties of micro-structures and constituents to expedite the design and structural optimization. [ABSTRACT FROM AUTHOR]

Manufacturing plays an important role in the properties of composites, which may lead to two types of uncertainties: (1) carbon fiber manufacturing deviations, such as the bean-shaped PAN carbon fibers, the lognormal-distributed fiber radius, etc. (2) composites manufacturing deviations, such as the inter-fiber voids and matrix voids. Although several experiments have been conducted to assess their effects on the mechanical properties of composites, a satisfactory result of quantitative characterization of fiber radius and fiber shape deviations and of matrix void content have not been obtained. In this paper, a parametric study based on the computational micromechanics is conducted to reveal the effects of fiber radius and fiber shape deviations and of matrix void content on the strengths and failure mechanisms of UD composites under four loading conditions, i.e. the transverse tension, compression, shear and longitudinal shear. Firstly, the constitutive laws of constituents, i.e. carbon fiber, matrix and interface, are established to characterize their mechanical responses. Then, the UD RVEs with fiber radius and fiber shape deviations and with matrix void are modeled individually based on experimental observation and statistical distribution. After qualitative validation of failure modes and quantitative validation of stress-strain curves, the methodology is applied to predict the stress-strain curves and failure modes of UD RVE with manufacturing uncertainties and the results show that not all manufacturing uncertainties have a detrimental effect on the mechanical properties of UD composites. [Display omitted] [ABSTRACT FROM AUTHOR]

Compared with traditional phenomenological models, concurrent multiscale simulation is a powerful tool to capture the mechanical behavior of composites from different scales simultaneously. However, it is still a challenge to conduct a concurrent multiscale simulation for composites due to the huge computational costs. The aim of this paper is to solve the challenge by introducing an effective reduced order model (ROM), called the data-driven self-consistent clustering analysis (SCA). The SCA method solves the RVE problem into two stages. In the offline stage, the high-fidelity RVE of composites is compressed into a cluster-based RVE and the interaction tensor between two clusters is calculated. In the online stage, a cluster-based discrete incremental Lippmann-Schwinger equation is solved to get the local strain and stress responses. Based on SCA, a concurrent multiscale framework SCA2 from microscale to mesoscale is proposed to capture the non-linear behavior of 3D braided composites. Firstly, the SCA-based results for yarn RVE and braided RVE are compared with the finite element (FE) results to verify the accuracy of the algorithm. Then, the SCA2 framework is applied to simulate the uniaxial tension and compression of 3D braided composites, which is also validated with the experiments and shows great accuracy and high efficiency. The proposed SCA2 framework will be extended into a three-scale concurrent simulation for the macroscopic structure analysis. [Display omitted] [ABSTRACT FROM AUTHOR]

• A SCA-based method is applied to study damage behavior of 3D braided composites. • The failure mechanisms are revealed by SCA only using hundreds of seconds. • The SCA is thousands of times more efficient than traditional FEM. • The SCA-based method can be used for concurrent multiscale analysis of composites. A data-driven self-consistent clustering analysis (SCA) method is applied to investigate the progressive damage behavior of 3D braided composites. The SCA-based method is split into the offline stage and the online stage. In the offline stage, the high fidelity RVE is compressed into a reduced RVE composed of several clusters. In the online stage, the mechanical responses are calculated by solving the discretized Lippmann-Schwinger integral equation. To validate the accuracy of proposed model, the SCA-based simulation is compared with the corresponding experiments and finite element analysis (FEA). The results show that the SCA method can accurately capture the stress and damage distribution, and the predictive stiffness and strength agree well with experimental data. More importantly, with the same constitutive laws and geometric model, SCA only takes a few hundred seconds, which is 1771 times faster than FEA. Because of the high efficiency, the SCA has the potential to be applied in concurrent multiscale analysis for braided composites. [ABSTRACT FROM AUTHOR]

A hierarchical multiscale model is established to reveal the failure mechanism of three-dimensional (3D) braided composites at high temperature. Firstly, the tensile and bending tests of the composites were performed at three different temperatures, and the properties of microscale constituents, i.e., carbon fiber, epoxy resin and interface, were also calibrated by experiments at different temperatures. Then, the elastic-plastic damage constitutive laws were proposed to characterize the mechanical behavior of microscale and mesoscale components. These constitutive models were implemented by a user-defined subroutine UMAT in ABAQUS. Finally, based on the homogenization procedure and the multiscale analysis method, the effects of temperature on microscale, mesoscale and macroscale properties of 3D braided composites were analyzed sequentially. The results showed that the temperature has the significant effects on the performances of 3D braided composites. With the increase of temperature, the properties of 3D braided composites decreased, and the failure modes changed from fiber breakage to matrix plastic deformation. Besides, the macroscopic simulation of strain fields agreed well with the DIC measurements and the temperature-dependent failure modes agreed well with SEM observation. It is expected that the established multiscale framework can predict high-temperature behavior of 3D braided composites and reveal the different failure mechanisms at different temperatures. Image 1 • The effect of temperature on the failure mechanism of 3D braided composites is revealed by experiments and simulation. • A hierarchical multiscale framework of the temperature-dependent elastic-plastic damage behavior is developed. • A full-scale FEM model is established to simulate the macroscale strain fields and compare with the DIC measurement. [ABSTRACT FROM AUTHOR]

• Propose a metal-isolator constitutive model based on parallel spring-slider model. • Friction coefficients of the sliders adhere to a predefined probability distribution. • All parameters of the model can be set from quasi-static compression test data. • This model is capable of high-precision nonlinear dynamic simulation. Metal rubber has been widely applied in the fields of structural vibration reduction and impact protection, due to its excellent mechanical properties. However, an accurate constitutive model of metal rubber to characterize its complex nonlinear mechanical behavior is still lacking. In this paper, a new constitutive model of metal rubber based on the Iwan model (parallel spring-slider model) is proposed, where the friction coefficient of sliders satisfy a given probability distribution. The nonlinear-elasticity and dry friction of metal rubber are considered in this model. The proposed model can characterize the mechanical behavior of metal rubber under the complex loading–unloading-reloading path. Furthermore, the constitutive model is used to simulate random vibration in time domain, and three nonlinear phenomena are simulated, which are consistent with the experiment. Based on the proposed model, a simplified and efficient model is also developed, which can be used for efficient computational. The proposed model would be an effective tool for quasi-static and vibration simulation of metal rubber. [ABSTRACT FROM AUTHOR]

The deformation distribution along the thickness direction of 3D woven composites under bending loading is inhomogeneous, and hence there is difficulty in numerically predicting the bending behavior of woven composites. This paper aims to propose a direct mesoscopic method for predicting the bending behavior of woven composites using the unit-cell finite element model. Firstly, four-point bending tests were conducted in the warp and weft directions, respectively. Then, the periodic boundary conditions are established for the unit-cell model with non-uniformly distributed deformations under pure bending loading. Finally, the bending properties and damage accumulation process of the woven composites are analyzed based on the elasto-plastic damage model with different mechanical properties in tension and compression. The simulated moment-curvature curves and failure modes are in good agreement with the experimental results. It is shown that the developed unit-cell finite element model can accurately predict the bending behavior of woven composites. [Display omitted] [ABSTRACT FROM AUTHOR]

Anisotropic stiffness properties of carbon fiber-reinforced polymer composites (CFRPCs) can be designed by arranging the fiber path. In this paper, we propose a novel method to optimize the fiber path using the genetic algorithms (GA) and simulated annealing algorithms (SAA) combined with the quasi-uniform cubic B-spline curves. The optimization goal is to obtain the largest reaction force of an open-hole plate under uniaxial tensile loading. After the finite element method (FEM) and experimental verifications, the optimized variable-stiffness specimen owes the higher strength and stiffness, compared with the unidirectional one. Besides, the stress concentration can be reduced. One of the key points of this paper is to use the GA and SAA to control the slight data points to optimize the B-spline curve. By reducing the number of optimization variables, the computational efficiency is improved greatly. Moreover, by increasing the interval variables of the B-spline curve, we further improve the accuracy of optimization results. The range of values for the control points can be easily adjusted according to the manufacturing and design requirements. We also compare the optimization results of GA and SAA. Both of them can get the similar optimization results, and the SAA has a better convergence speed and accuracy. The proposed optimization method can be extended for three-dimensional preform and structure design in the future. [ABSTRACT FROM AUTHOR]

Calendering is an essential step in the manufacturing process of lithium-ion batteries. However, the intrusion of active particles into metal foil can damage the current collector during calendering. Here, we investigate the changes in surface morphology and the tensile properties of current collector after calendering. The damage mechanisms of tensile strength reduction for current collector due to compressive pressure are revealed by combining the calendering tests, tensile experiments, and simulations. Specifically, the DEM-FEM scheme is proposed, which combines the discrete element method (DEM) with the finite element method (FEM) to characterize the mechanical behavior of current collectors after the intrusion of active particles. The results show that the current collectors become more brittle and vulnerable with the increase of compressive pressure. Finally, the failure phase diagrams are presented during the winding and electrochemical processes. This study can reveal the failure behavior of current collectors and guides the electrode manufacturing optimization. [Display omitted] • A computational framework is developed for active particles pressed into the foil. • The evolution of surface morphology and mechanical properties of the current collector is revealed during calendering. • The effect of calendering pressure on current collectors is introduced into the winding process to optimize manufacturing. [ABSTRACT FROM AUTHOR]

Abstract This paper presents a unified theory of yield and failure criteria for unidirectional polymer-matrix composites (UD PMCs). This interactive unified theory considers the effect of normal stress on the shear strength by introducing a coupling term ( q 3 σ 22 | τ 21 |). The coefficient q 3 of the coupling term is an empirical value and equals to 0.2. The predictions of the unified theory are well agreeable with present and existing experiments. Furthermore, Tao theory has been improved by adding the limiting condition that the ratio of compressive strength to shear strength should be greater than two. [ABSTRACT FROM AUTHOR]

Ultrasonic welding technology represents an advanced method for joining thermoplastic composites. However, there exists a scarcity of systematic investigations into welding parameters and their influence on the morphological characteristics and quality of the welded regions. Furthermore, a comprehensive experimental understanding of the welded joint failure mechanisms remains deficient. A robust model for simulating the failure behavior of welded joints under loading has yet to be formulated. In this study, ultrasonic welded specimens were fabricated using distinct welding control methods and varied parameter combinations. Diverse experimental methodologies are employed to assess the morphological features of the welded areas, ascertain specimen strength, and observe welding interface failure modes. Based on a cohesive model, a finite element model is developed to predict the strength of the ultrasonic welded joints and elucidate the failure mechanisms. The results showed that, under identical welding parameters, the specimens welded with a high amplitude and low welding force exhibit superior welding quality. The specimens produced under displacement control exhibit minimal dispersion in strength. The proposed finite element model effectively prognosticates both welded joint strength and failure modes. [ABSTRACT FROM AUTHOR]

Thermal protection is one of the crucial issues for the advanced propulsion systems of Reusable Launch Vehicles. New service requirements for materials, such as high strength, low density, low thermal expansion, high thermal stability, etc., are raised for the thermal structure with the increasing demand of flight Mach numbers and thrust‐to‐weight ratio. Carbon fiber‐reinforced ceramic composites, which generally meet the aforementioned requirements, show great potential for various applications and they have been widely applied in the thermal protection for hypersonic vehicles. This paper gives a comprehensive and systematic review of current research status for carbon fiber‐reinforced ceramic composites applied in the thermal structure of advanced propulsion systems. Three aspects are presented and discussed: the ceramic composites fabrication and the property characterization, the thermal performance of composite thermal structure used in practical engines, and the numerical methods for predicting mechanical and thermal properties of composites as well as the physicochemical phenomenon in the cooling channels. Firstly, the main manufacturing processes for the carbon‐reinforced ceramic composites are presented and the corresponding advantages and disadvantages are analyzed. The high‐temperature oxidation and ablation behaviors of composites are demonstrated and the improvement of oxidation and ablation resistance by introducing the ultra‐high‐temperature ceramics into C/C composites is discussed in detail. Then, several typical applications of carbon fiber‐reinforced ceramic composites (mainly C/SiC), including the work of RCI, JAXA and NASA, have been reviewed and analyzed. After that, the current research status of macroscale equivalent and multiscale numerical methods for predicting the mechanical and thermal properties of composites as well as the complex physicochemical phenomenon occurring in hydrocarbon fuels are sorted out. Finally, several potential prospects are pointed out for the future research on the thermal protection of advanced propulsion systems based on the carbon fiber‐reinforced ceramic composites. [ABSTRACT FROM AUTHOR]

Concurrent analysis of composite materials can provide the interaction among scales for better composite design, analysis, and performance prediction. A data-driven concurrent n-scale modeling approach ( FExSCA n-1 ) is adopted in this paper for woven composites utilizing a mechanistic reduced order model (ROM) called Self-consistent Clustering Analysis (SCA). We demonstrated this concurrent multiscale modeling theory with a FExSCA 2 approach to study the 3-scale woven carbon fiber reinforced polymer (CFRP) laminate structure. FExSCA 2 significantly reduced expensive 3D nested composite representative volume element (RVE) computation for woven and unidirectional (UD) composite structures by developing a material database. The modeling procedure is established by integrating the material database into a woven CFRP structural numerical model, formulating a concurrent 3-scale modeling framework. This framework provides an accurate prediction for the structural performance (e.g., nonlinear structural behavior under tensile load), as well as the woven and UD physics field evolution. The concurrent modeling results are validated against physical tests that link structural performance to the basic material microstructures. The proposed methodology provides a comprehensive predictive modeling procedure applicable to general composite materials aiming to reduce laborious experiments needed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Considering the locally-variable-amplitude fatigue loading induced by the stress redistribution. • The entire fatigue damage process is divided into gradual degradation and sudden degradation. • The influence of architectures on fatigue damage mechanism is revealed. • An exponential damage evolution law is adopted to characterize the elastic–plastic damage of the matrix. The fatigue-induced stress redistribution in three-dimensional (3D) braided composites, even when subjected to externally constant-amplitude fatigue loads, results in locally-variable-amplitude fatigue loading, significantly impacting their fatigue performance degradation. This paper is aimed to propose a novel fatigue damage analysis method to predict the fatigue behavior of 3D braided composites subjected to locally-variable-amplitude loading. To this end, the continuous damage method, residual strength, residual stiffness, and fatigue life models are combined to characterize the properties degradation of 3D braided composites with cycling. Once stress redistribution occurs, the fatigue properties degrade based on the new stress level, and the equivalent cycle number is recalculated accordingly. As the material undergoes different cycle blocks, damage accumulates, ultimately leading to failure when the overall stiffness of the material degrades to 80%. Traditional fatigue models are also employed to predict the fatigue behavior of representative volume elements for comparison. The results predicted by the present model shows good agreement with experiments. Furthermore, the influence of stress levels and architectures of 3D braided composites on fatigue performance is systematically discussed. [ABSTRACT FROM AUTHOR]

Due to the mismatch of the thermal expansion coefficients between the matrix and yarns, thermal residual stress will appear in C/SiC composites. In this paper, a progressive damage model was used to predict the thermal-mechanical behavior of C/SiC composites and reveal the failure mechanism. Firstly, the properties of the composites under tensile load were tested at three different temperatures in vacuum. Then, the elastic-plastic progressive damage constitutive laws were used and implemented by a user-defined subroutine UMAT in ABAQUS. The thermal residual stress evolution in the cooling and heating processes was characterized. Finally, the stress-strain curves of the composites under tensile load at different temperatures were studied. The effects of thermal residual stress on the tensile properties and progressive damage process of C/SiC composites were revealed sequentially. This work can give design guidance for strengthening of C/SiC composites. [ABSTRACT FROM AUTHOR]

Lattice materials at micro scale with extraordinary stiffness and strength have demonstrated promising industrial application potentials in aerospace, transport, automotive, biomedical and other sections. However, the complex fabrication process at micro scale will inevitably induce stochastic geometric defects within as-fabricated lattice materials, thus quantitatively evaluation of the mechanical integrity of 3D-printed micro lattice structures becomes a critical important issue. In this paper, mechanical behavior of the micro Schwarz Primitive triply periodic minimal surfaces (P-TPMS) cylinder shell structures fabricated with projection micro-stereolithography (PμSL) 3D printing technique were investigated. Meanwhile, synchrotron X-Ray micro-tomography (SR-μCT) 3D imaging and interrupted in-situ compression experiment were employed for quantifying the effect of defects on the compression mechanical performances. It is found that the thickness along vertical direction was larger than along horizontal direction. Afterwards, three different types of finite element models were developed for understanding the effects of fabrication defects on the mechanical behavior characteristic. Simulation results demonstrated that the statistical model was more accurate and efficient when compared with the ideal model and real geometry reconstructed model. Finally, parametric study was also presented to gain insight into the role of thickness imperfections on the mechanical performance of the shell. [ABSTRACT FROM AUTHOR]

Due to the excellent mechanical and chemical properties at ultra-high temperature, ceramic matrix composites have been promising candidates for lightweight design of future thermal protection systems (TPSs). In this work, C/SiC composite corrugated lattice core sandwich panels (LCSPs) are fabricated and their thermal insulation performances are measured by a self-developed heating system combined with infrared thermal imaging (ITI) technology. Experimental results show that the thermal insulation effect increases with core inclination angle. A new model for predicting equivalent thermal conductivity (ETC), which considers the thermal conduction, cavity radiation, thermal convection and surface radiation is established to explain why the experimentally measured ETC is lower than the predicted value of previous work. Through theoretical analysis, we find that the cavity radiation plays a dominated role in ETC prediction. To reduce or inhibit the cavity radiation, multilayer LCSPs and one-layer LCSP filled with aerogel are designed. Finite element analysis results show that two-layer LCSP is the best solution for multilayer LCSP, and the maximum ETC of one-layer LCSP filled with aerogel only is 0.226 W/(m K), much lower than that of C/SiC composite. We investigate the heat transfer mechanism and thermal insulation performance of fabricated C/SiC corrugated LCSP using experimental, theoretical and numerical simulated approaches. [ABSTRACT FROM AUTHOR]

In recent years, ceramic matrix composite (CMC) lattice structure has become a promising candidate for a new generation of integrated thermal protection systems (ITPSs) used in the ultrahigh-temperature environment. However, the thermal short circuit effect caused by lattice cores limits their application. In this work, we propose a bilayer CMC lattice structure filled with phase change material (PCM) and thermal insulation material for integrated thermal protection systems (ITPSs) to mitigate the thermal short circuit effect. The numerical simulation method is used to verify the effectiveness of the bilayer lattice structure in mitigating the thermal short circuit effect compared with one-layer ITPS. By inserting the middle face sheet, the thermal insulation effect enhances about 16%. Furthermore, the effects of thermal insulation materials, thermal conductivity and thickness of paraffin/expanded graphite composite PCM, and the diameter of the lattice core strut on the thermal insulation performance are discussed. The results show that the thickness of PCM has an optimal solution. Optimizing results show that when the aerogel insulation fiber is used as the thermal insulation material, the thermal conductivity k=0.82 W/(m⋅K) and the thickness t3=10 mm of PCM, the diameter of the core strut d=1.5 mm, the bilayer PCM-ITPS has the best thermal insulation performance. When the ultrahigh-temperature load is continuously loaded, the highest temperature of Top Face Sheet is more than 2300 °C, but the highest temperature of Bottom Face Sheet is only 30.12 °C, which thermal insulation effect is far better than the traditional ITPS. This work gives a novel scheme to solve the thermal short circuit effect, improving the thermal protection performance and accelerate the application of lattice structure in ITPS. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel methodology is presented for creating high-fidelity models considering the real paths of the fibers from microscopic images. • Effects of embedded wrinkles on the compressive failure mechanism of thick unidirectional glass fiber-reinforced composites are studied by FE simulation. • Good agreement is found between the three-dimensional progressive damage analysis method and compression experiment results. • Both the amplitude and maximum angle of the embedded wrinkle are the key parameters affecting compressive strength. In thick unidirectional glass fiber-reinforced composites, the out-of-plane embedded wrinkle flaws have a major impact on compressive failure, which should be taken into account and assessed during the design, manufacturing, and inspection phases. The thick unidirectional coupons with embedded wrinkles of various severities were manufactured and tested. The deformation of the wrinkle region was captured by the Digital Image Correlation (DIC). As the wrinkle angle increased, the compressive failure stress decreases and the modulus does not change significantly, while the wrinkle amplitude has a negative effect on both the compressive failure stress and elastic modulus. The linear texture image regression approach is used to account for the path of fibers. The high-fidelity three-dimensional finite element (FE) models considering the real paths of the fibers are established. To reveal the interplay and impact of wrinkle severity parameters on the compressive failure behavior of composites, the progressive damage analyses and cohesive elements are also incorporated. Compared with the experiments, the FE studies accurately identify the dominant failure modes and failure stress values for various wrinkle severity parameters. [ABSTRACT FROM AUTHOR]

Keywords: ceramics; composite material; propulsion systems; regenerative cooling; thermal protection system EN ceramics composite material propulsion systems regenerative cooling thermal protection system 1 1 1 04/18/23 20230401 NES 230401 The Front Cover depicts an advanced propulsion system. Cover Picture: Application of Carbon Fiber-Reinforced Ceramic Composites in Active Thermal Protection of Advanced Propulsion Systems: A Review (Chem. Rec. 4/2023) Ceramics, composite material, propulsion systems, regenerative cooling, thermal protection system. [Extracted from the article]