Woven Ceramic Matrix Research Articles

Finite element modeling of viscoelastic creep behavior and transverse cracking in fiber-reinforced composite materials

Fiber-reinforced composites are essential in the aerospace industry, highlighting the need for an in-depth understanding of their durability. This study introduces a novel approach that integrates viscoelasticity and damage evolution based on continuum damage mechanics, employing finite element analysis. The method utilizes an anisotropic viscoelastic constitutive law to examine creep behavior under constant stress, decomposing stresses into equilibrium and non-equilibrium components. Moreover, it integrates a transverse crack damage variable associated with crack density. After solving stiffness equations, a detailed analysis of transverse crack propagation is conducted. This technique was applied to creep tests on carbon fiber-reinforced plastics and 3D woven ceramic matrix composites, resulting in strain and crack density profiles. The numerical simulations successfully reproduced experimental outcomes. The developed method offers a comprehensive tool for analyzing transverse crack propagation under viscoelastic creep conditions through finite element analysis, significantly enhancing design considerations by incorporating aspects of long-term durability.

Stochastic Simulation of Thermal Residual Stress in Environmental Barrier Coated 2.5D Woven Ceramic Matrix Composites

Stochastic Simulation of Thermal Residual Stress in Environmental Barrier Coated 2.5D Woven Ceramic Matrix Composites

Multi-scale collaborative design method for macroscopic thermal optimization and mesoscopic woven structure of hypersonic vehicle’s TOCMC leading edge

Multi-scale collaborative design method for macroscopic thermal optimization and mesoscopic woven structure of hypersonic vehicle’s TOCMC leading edge

Mechanical Characterization of Bi-Layer Environmental Barrier Coatings Under Tension and Bending Using Acoustic Emission and Digital Image Correlation

Abstract Fracture characteristics of bi-layer environmental barrier coatings (EBC) deposited on a woven ceramic matrix composite (CMC) substrate using air plasma spray processes were investigated under uni-axial tension and bend tests at room temperature. Health monitoring techniques such as acoustic emission (AE) and digital image correlation (DIC) were employed to better understand the cracking behavior of the coating and its progression. Post-test microscopy was performed to correlate the coating cracks with DIC and AE location. The results indicate that multiple transverse cracks first occurred in the coating, followed by substrate transverse cracks and additional coating cracks. DIC analysis was able to highlight the formation and location of these cracks. The fracture strength of the coating was estimated assuming the composite beam theory.

Damage mechanism characterisation of plain weave ceramic matrix composites under in-plane shear using in-situ X-ray micro-CT and deep-learning-based image segmentation

Damage mechanism characterisation of plain weave ceramic matrix composites under in-plane shear using in-situ X-ray micro-CT and deep-learning-based image segmentation

Uncertainty quantification and propagation in the microstructure-sensitive prediction of the stress-strain response of woven ceramic matrix composites

Uncertainty quantification and propagation in the microstructure-sensitive prediction of the stress-strain response of woven ceramic matrix composites

Woven ceramic matrix composite surrogate model based on physics-informed recurrent neural network

• Recurrent neural network-based surrogate model for nonlinear, non-monotonic CMC constitutive response presented. • Physics-informed constraints employed through regularization to enforce requisite physics. • Surrogate model accurately represents non-monotonic, included reversed loading, behavior of multiple textile CMC material systems. • Efficiency over multiscale numerical approach improved several orders of magnitude. A recurrent neural network (RNN) based surrogate model is developed to emulate the nonlinear constitutive behavior of woven ceramic matrix composites (CMCs) driven by matrix damage at multiple length scales. Physics-informed constraints are introduced into the surrogate model through regularization to ground the prediction in physics and improve its predictive capabilities. Training data is generated using the multiscale generalized method of cells (MSGMC) approach coupled with a matrix damage model. This coupling permits simulating the nonlinear behavior of woven CMCs based on constituent response at the micro-, meso-, and macroscales. The multiscale repeating unit cell is loaded under non-monotonic conditions including multiple load / unload cycles and tension / compression. The fiber volume fraction as well as the intra- and intertow void volume fractions are also varied in the generation of training data. Therefore, the RNN-based surrogate model is tasked with predicting, as a function of variable input strain sequence and fiber and void volume fractions, the resulting stress versus strain response while satisfying physical constraints such as positive semi-definiteness of the tangent stiffness matrix and linear elastic unloading. The trained surrogate model effectively matches the stress versus strain response and successfully predicts the tangent modulus throughout the loading regime. Neural network based surrogate models can offer efficient alternatives to running computationally intensive multiscale material models to simulate the nonlinear response of large structural models. Therefore the presented work provides evidence towards the feasibility of developing, training, and running such models for CMCs with complex architectures, nonlinear multiaxial material response, and under non-monotonic loading conditions.

Thermal and Mechanical Properties of Plain Woven Ceramic Matrix Composites by the Imaged-Based Mesoscopic Model

The mesoscopic finite element model of ceramic matrix composites is developed by reconstructing computed tomography images. The relationship between microstructure and macroscopic properties and their dispersion are explored. Firstly, a three-dimensional reconstructed computed tomography model was carried out to calculate the orientation of the components. Secondly, the orientation and gray value of images were used to identify the basic structure of composites including fiber tows, matrix, and porosities. Finally, the two-dimensional finite element model was developed to analyze the macroscopic thermal and mechanical properties. The numerical results showed that: (1) the geometries and distributions of pores had a significant effect on the through-thickness modulus and thermal conductivity; (2) the stress and heat flow concentration area on the material surface usually occurred in narrow gaps between closely spaced longitudinal tows; (3) the elastic modulus and thermal conductivity were dispersive, and their distribution followed by two-parameter Weibull distribution.

Damage mechanisms of 2.5D SiO2f/SiO2 woven ceramic matrix composites under compressive impact

Fiber-reinforced SiO 2f /SiO 2 woven ceramic matrix composites (CMCs) are widely applied in the aeronautics and astronautics field due to their many physical and chemical advantages. However, compressive impact loads affect many application scenarios; thus, the damage morphologies and failure modes of these composites under compressive impact should be studied, particularly in the through-thickness direction. In this study, a comparative analysis using the split Hopkinson pressure bar (SHPB) experiment and finite element analysis (FEA) model revealed the damage mechanisms. The compressive impact was simulated in Abaqus/Explicit, and the cohesive element was selected to simulate cohesion of the interface according to the Hashin criterion for multi-mode failure. The results show that 2.5-dimensional SiO 2f /SiO 2 woven CMCs do not have sufficient plasticity to restrain the propagation of micro-cracks under high strain rates after the elastic stage under compressive impact. Many micro-cracks propagated and formed large cracks in the adiabatic shear zone. The adiabatic shear zones were generated when a compressive impact load was applied to the SiO 2f /SiO 2 CMCs at a high strain rate, and these impacts deformed the SiO 2f /SiO 2 CMCs. The adiabatic shear zone occurred at a high strain rate at the weakest point inside the fields of the SiO 2f /SiO 2 CMCs. The micro-cracks propagated and accumulated in this zone. Plastic fracture is the major failure mode for the SiO 2f /SiO 2 CMC specimens; this failure was characterized by fiber yarn fracture and the formation of micro-voids and micro-cracks due to matrix fracture. The large cracks, new voids, and interfacial debonding lead to the failure of the SiO 2f /SiO 2 CMCs. Combined action due to micro-crack formation and its propagation in the adiabatic shear band leads to a softening mechanism of the strain rate.

Mechanical behavior of woven CMCs under non-uniform stress and strain fields

Woven ceramic matrix composites (CMCs) hot-section components will sustain spatially non-uniform stress and temperature fields in service, and the mechanical response in CMCs under inhomogeneous stress and strain fields remains indistinct. This study focuses on one noteworthy aspect of this issue: the effects of weave architecture on the mechanical response of CMCs under off-axis and thermomechanical loading. To this end, the stress and strain evolution of wavy tows in CMCs are investigated by establishing a meso-scale finite element model , which reflects the real weave architecture. Besides, the model is verified by comparing the predicted results with the experimental results of a representative woven CMC. The strain and stress concentrations appear at the location of tow cross-overs because of the bending and straightening of tows, resulting in the woven composites strength may be inferior to that of laminate composites . Although the scope of this work is limited to one type of weaving, it is expected that the modeling method can be useful in examining other types of weaving. • The mechanical behavior of woven CMCs are studied by establishing a meso-scale FE model. • Stress and strain evolution of wavy tows are studied under non-uniform stress and strain fields. • The maximum stress and strain appear at the edge of tow crossovers, due to bending and straightening. • Strength of woven composites is inferior to that of laminate composites due to weave architecture.

Shear failure evolution and its dispersion of plain woven ceramic matrix composites z‐pin structure

AbstractIn this paper, the digital image correlation technique was applied to the shear test of 2D SiC/SiC composites z‐pin with the purpose of analyzing the shear behavior of the plain woven pin and studying the structure factors of test results dispersion. After obtaining the strain–stress curves of the joint's connection region, the evolution of z‐pin shear failure process was investigated. The z‐pin's failure fractures were observed, and the main factors of its dispersion of shear mechanical properties were discussed. Changing the yarn parameter of model building and importing into Workbench for calculation, the average stress results in the shear plane were obtained. Different simulation results show that optimization of plain‐woven pin structure parameters can effectively improve its shear strength.

Understanding the machining characteristic of plain weave ceramic matrix composite in ultrasonic-assisted grinding

The machining of silicon carbide (SiC) ceramic matrix composites is a significant challenge because of the severe material damage that may occur during material removal, which might shorten the service life of the composite parts. In this study, the effects of different fibre orientations of two-dimensional woven carbon-fibre-reinforced silicon carbide matrix composites (2D-C f /SiC) on the grinding force, surface roughness, and surface/subsurface micromorphology were investigated to clarify the material removal and breakage mechanism in ultrasonic-assisted grinding of ceramic matrix composites. The results show that the predominant material removal mode in ultrasonic-assisted grinding is brittle fracture. The forms of material breakage are matrix cracking, fibre fracture, fibre pull-out, interfacial debonding, and interfacial fracture. Compared with conventional grinding, the normal force, tangential force, and surface roughness in ultrasonic-assisted grinding decreased by approximately 20%, 18%, and 9%, respectively. The machining parameters significantly impacted the grinding force and surface roughness. The material removal modes varied for different fibre orientations. Ultrasonic-assisted grinding can effectively decrease the grinding force and improve the surface integrity. The findings of this study can be applied to predict the grinding force and surface integrity of 2D-C f /SiC and contribute to the design and manufacturing of this type of material.

The design of special woven-preformed structures for the high-performance film cooling with undamaged fibers based on 2.5D ceramic matrix composites

A design-manufacturing integration method for the film cooling of 2.5D woven ceramic matrix composites (CMC) is proposed which can concurrently achieve film holes with undamaged fibers and improve cooling performance. Meanwhile, this study investigates the effect of different woven-preformed structures on gas-thermal-mechanical characteristics. The design-manufacturing integration method implements the collaborative design of the micro woven structure and macroscopical shaping of film holes. Firstly, the unique micro woven method can manufacture the film holes without damaged fibers which effectively guarantees the strength of CMC. Secondly, the macroscopically shaped special woven-preformed holes (SWPHs) own the special structural features related to woven structure. These special structures change the flow field and induce the counter-rotating/anticounter-rotating Vortex Pair (CVP/Anti-CVP) which effectively improves the cooling performance and controls the thermal stress. Compared with traditional drilled cylindrical hole DCH, the SWPHs’ maximum increase of averaged overall film cooling effectiveness reaches 110%. Besides, SWPHs avoid the large temperature difference between the yarn and the matrix around the drilled DCH which eventually reduces the thermal stress in the corresponding area.

Reduced-order models for microstructure-sensitive effective thermal conductivity of woven ceramic matrix composites with residual porosity

This paper presents a data-driven framework for the development of reduced-order models to predict microstructure-sensitive effective thermal conductivity of woven ceramic matrix composites (CMCs) with residual porosity . The main components of the proposed framework include (i) digital generation of representative volume elements (RVEs), (ii) estimation of the effective thermal conductivities of the RVEs using finite element (FE) models, (iii) low dimensional representation of the microstructure in the RVEs using 2-point spatial correlations and principal component analysis (PCA), and (iv) an active learning strategy based on Gaussian process regression (GPR) that minimizes the size of the training dataset through the selection of microstructures with the highest potential for information gain. The reduced-order models are demonstrated to provide high fidelity predictions on new RVEs.

Micromechanical modeling for the in-plane mechanical behavior of orthogonal three-dimensional woven ceramic matrix composites with transverse and matrix cracking

Ceramic matrix composites (CMCs) are currently being considered for applications in the hot-section components of aviation gas turbines owing to their favorable characteristics. Herein, a micromechanical modeling is presented for orthogonal 3 D woven CMCs under in-plane loading. The three-dimensional effective compliance of the 3 D woven composite was derived using three-dimensional laminate theory and continuum damage mechanics. The damage variables were used to describe the stiffness reduction due to the transverse and matrix cracking in each fiber bundle. The calculation method for the transverse and matrix cracking evolutions under in-plane loading was established by introducing mixed-mode damage criteria. The stress redistribution among the fiber bundles of 3 D woven CMCs due to the fiber/matrix interfacial debonding around matrix cracking was considered to capture the interaction between the matrix and transverse crack evolutions. Additionally, a mesomechanical model comprising finite element analysis and damage mechanics was established to evaluate the stress perturbation due to the geometry of the woven structure. The edge face of the 3 D woven CMC was experimentally observed to measure the transverse and matrix cracks that occurred in each fiber bundle. The transverse and matrix crack densities predicted by the micromechanical and mesomechanical models reasonably agreed with the experimental results up to crack saturation. Furthermore, the micromechanical model reproduced the nonlinear stress–strain response under tensile and shear loading using mixed-mode damage criteria.

Multiscale temperature-dependent ceramic matrix composite damage model with thermal residual stresses and manufacturing-induced damage

This work presents a multiscale thermomechanical simulation framework to capture the temperature-dependent damage behavior of woven ceramic matrix composites (CMCs). The framework consists of cooldown simulations, which capture a realistic material initial state, and subsequent mechanical loading simulations to capture temperature-dependent nonlinear stress–strain behavior. The cooldown simulations result in a realistic material initial state with thermal residual stresses and damage hotspots that occur due to constituent property mismatch and post-manufacturing cooldown. A fracture mechanics-informed thermomechanical progressive damage model is extended to capture the manufacturing-induced damage that occurs because of the high thermal residual stresses and to simulate the mechanical response of two-dimensional (2D) plain weave carbon (C) fiber, silicon carbide (SiC) matrix (C/SiC) CMCs at temperatures ranging from room temperature (RT) to 1200 °C. A combination of temperature-dependent material properties and damage model parameters are included in the model to simulate the effects of temperature on deformation and damage behavior. Model calibration was conducted using quasi-static tensile experimental data from the literature for RT, 700 °C, and 1200 °C and the nonlinear, temperature-dependent predictive capabilities of the reformulated model are demonstrated for 1000 °C. The model is also applied to simulate the temperature-dependent thermomechanical response of a 2D woven five harness satin (5HS) SiC/SiC CMC at RT and 1200 °C and shows excellent agreement with experiments.

Improved semi-analytical and numerical methods on prediction of in-plane coefficients of thermal expansion of woven ceramic matrix composite considering defects

Abstract The in-plane coefficients of thermal expansion (CTEs) are important parameters of woven ceramic matrix composite (CMC) in the processes of design, manufacture and utilization. In this paper, five-harness satin woven C/C composites with different volume fractions of matrix fabricated by precursor infiltration and pyrolysis (PIP) method are used for microstructure observation and in-plane CTEs tests. The morphological features and evolution process of defects are studied via analysis of scanning electron microscope (SEM) figures. The improved semi-analytical method and the improved finite element method (FEM) on prediction of the equivalent in-plane CTE of woven CMC considering the effects of defects are established. The improved methods are validated by the results of experiments. Therein the improved semi-analytical method is more efficient in calculation. The improved FEM needs to establish complicated finite element models, but it can reveal the structural details and the deformation mechanism after heating.

Multiscale modeling and failure analysis of an 8-harness satin woven composite

Abstract 8-harness satin (8HS) woven composites display complex architecture and a certain feature of mutually orthogonal reinforcement, which arise particular interest for aerospace structural groups. In this study, based on realistic geometry parameters and material property, multiscale finite element models of an 8HS woven composite are established. The effective properties of fiber bundles can be obtained by the micro-scale model and then used in the meso-scale model. The meso-scale model is established to predict the global failure behavior of 8HS woven composites under tensile load using the periodic boundary conditions. The predict results are compared to experiments from tensile tests and microstructure analysis on oxide/oxide 8HS woven ceramic matrix composites. The good correlation of the comparison shows that the multiscale modeling approaches can accurately predict the mechanical properties and failure mechanism of 8HS woven composites under plane tensile load when considering the particular material features.

Development of a novel damage approach on the microstructure for modeling woven ceramic matrix composites

AbstractCeramic Matrix Composites (CMC) overcome limitations associated with classical technical ceramics e.g. low fracture toughness and brittle failure under mechanical or thermomechanical loading [1]. Their high temperature stability and low weight makes them attractive for use in various fields, especially aerospace industry, where they improve engine efficiency compared to metal components. However current CMCs lack well established material property design databases for a reliable use in critical aerospace structures. Demonstrating the durability of this relatively new class of materials is the challenge to face and therefore the failure mechanisms need to be investigated further. This contribution deals with the successive development of a woven representative volume element (RVE) for arbitrary CMCs. In contrast to previously developed continuum mechanical or laminate theory based modeling approaches, the introduced model combines various damage formulations. The fiber bridging effect, resulting from the weak interface bond of matrix and reinforcement, is governed by the use of cohesive zone (CZ) elements [2]. Whereas the matrix damage is represented using a continuum mechanical approach [3].

Investigation on non-uniform strains of a 2.5D woven ceramic matrix composite under in-plane tensile stress

Abstract In this study, the digital image correlation technique and strain gauges were applied to the in-plane tensile tests of a 2.5D woven ceramic matrix composite for the purpose of characterizing deformation and strain distribution features. The test results indicate a strong influence of the weave architecture on the strain distribution of the material. Mesoscale finite element models were established based on the weave architecture of the material. The experimental and simulation results show that: the strain distributions are periodic and fluctuating; the maximum strain fluctuation on the surface is about 30%, but the deviation of average strain decreases rapidly with the calculated area increase. The strain measurement methods were proposed to obtain the accurate average strain: the size of measurement/calculated area should be twice larger than the unit cell size; much more accurate result could be obtained when the area size is an integer multiple of the unit cell size.