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Multiscale ceramic matrix composite thermomechanical damage model with fracture mechanics and internal state variables

机译：多尺度陶瓷矩阵复合热机械损伤模型与骨折力学和内部状态变量

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摘要

This work presents a multiscale damage model that accounts for ceramic matrix composite (CMC) length scale dependent behavior, including scale-specific brittle matrix damage initiation and propagation. Internal state variable theory is implemented to obtain the stress-strain constitutive relationship for damaged ceramic matrix material using damage variables which capture the effects of matrix cracking and nucleation and growth of matrix porosity. Matrix cracking is modeled using a damage variable determined using fracture mechanics and the self-consistent scheme. This methodology provides an effective way to model the effects of matrix cracks which initiate when stress intensity factors exceed the fracture toughness of the material, and whose growth is governed by crack growth kinetics. An additional source of material nonlinearity, matrix porosity, occurs as a result of material diffusion around grain boundaries and is related to the material entropy dissipation. These effects are captured using a porosity state variable that is explicitly related to the volumetric strain. The nonlinear predictive capabilities of the material model are demonstrated for monolithic silicon carbide, unidirectional (UD) carbon fiber/silicon carbide matrix (C/SiC) CMC, and five-harness satin (5HS) woven C/SiC CMC. The model predictions are in excellent agreement with experimental observations for 2D woven C/SiC CMCs from literature.
机译：这项工作介绍了多尺度损伤模型，用于占陶瓷矩阵复合（CMC）长度尺度依赖性行为，包括比例特异性脆性矩阵损伤启动和传播。实施内部状态可变理论以获得使用损伤变量的损伤陶瓷基质材料的应力 - 应变组成型关系，该损伤变量捕获基质裂化和成核和基质孔隙率的生长。使用使用裂缝力学和自我一致的方案确定的损伤变量建模矩阵裂纹。该方法提供了模拟基质裂缝效果的有效方法，该裂缝在应力强度因子超过材料的断裂韧性时，其生长受裂纹生长动力学的增长。由于晶界周围的材料扩散而发生额外的材料非线性基质孔隙源，并且与材料熵耗散有关。使用与体积应变明确相关的孔隙态变量捕获这些效果。材料模型的非线性预测能力被证明单片碳化硅，单向（UD）碳纤维/碳化硅基质（C / SiC）CMC和五线缎（5HS）编织C / SiC CMC。模型预测与来自文献的2D编织C / SiC CMC的实验观察结果非常一致。

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