Abstract

The current research work presents the computational micromechanical analysis of the room temperature tensile failure behavior of unidirectional (UD) and cross-ply (0/90) ceramic matrix composites (CMCs). For computational micromechanical analysis, three-dimensional (3D) representative volume element (RVE) and multi-fiber multilayer RVE (M² RVE) models are generated that are representative of the lamina and the laminate under investigation. The RVE and M² RVE models are generated by replicating the fiber distribution, and the placement of the fibers observed in a microscopic image of an actual CMC laminate. The generated RVE models consist of the discrete representation of individual constituent phases of the CMC such as fibers, interphase, matrix, and the fiber–interphase interface region. Under the applied external tensile load, the fiber–interphase interface interactions are modeled using the cohesive elements that follow the bilinear traction separation law. The matrix, fiber, and interphase materials failure behavior is captured using a brittle cracking model. In order to validate the proposed numerical methodology, the predicted average stress–strain curve at the UD laminate level is compared to the experimental stress–strain curve reported in the literature. In addition, the observed different phases in the predicted stress–strain curve are validated with the literature data. Using the proposed numerical methodology, a detailed local stress–strain and damage analysis leads to an observation that the so-called ductile stress–strain behavior (kink in the stress–strain curve) of a CMC UD laminate under uniaxial fiber direction tensile loads is mainly caused by the matrix damage initiation. Apart from the SiC material properties such as strength and fracture energy, it is also observed that the RVE size influences the average strength and failure strain predictions using computational micromechanics.

中文翻译：

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纤维方向单轴拉伸载荷下单向陶瓷基复合材料层合板和交叉层板的破坏分析：内聚区模型和脆性断裂力学方法

摘要

当前的研究工作提出了单向（UD）和交叉（0/90）陶瓷基复合材料（CMC）室温拉伸破坏行为的计算微力学分析。为了进行计算微机械分析，生成了三维（3D）代表性体积元素（RVE）和多纤维多层RVE（M ² RVE）模型，这些模型代表了所研究的层板和层压板。RVE和M ²RVE模型是通过复制纤维分布以及在实际CMC层压板的显微图像中观察到的纤维位置生成的。生成的RVE模型包括CMC各个组成相的离散表示，例如纤维，相间，基体和纤维-相间界面区域。在施加的外部拉伸载荷下，使用遵循双线性牵引力分离定律的内聚元素对纤维-相间界面相互作用进行建模。使用脆性裂纹模型可以捕获基体，纤维和相间材料的破坏行为。为了验证提出的数值方法，将UD层压板水平的预测平均应力-应变曲线与文献中报道的实验应力-应变曲线进行了比较。此外，预测的应力-应变曲线中观察到的不同相位已通过文献数据进行了验证。使用所提出的数值方法，详细的局部应力-应变和损伤分析导致观察到，在单轴纤维方向拉伸载荷下，CMC UD层压板的所谓延性应力-应变行为（应力-应变曲线中的扭结）为主要是由基质破坏引发引起的。除了SiC材料的特性（例如强度和断裂能）外，还可以观察到RVE尺寸会影响使用计算微力学预测的平均强度和破坏应变。详细的局部应力-应变和损伤分析导致观察到，在单轴纤维方向拉伸载荷下，CMC UD层压板的所谓延性应力-应变行为（应力-应变曲线中的扭折）主要是由基体损伤引起的引发。除了SiC材料的特性（例如强度和断裂能）外，还可以观察到RVE尺寸会影响使用计算微力学预测的平均强度和破坏应变。详细的局部应力-应变和损伤分析导致观察到，在单轴纤维方向拉伸载荷下，CMC UD层压板的所谓延性应力-应变行为（应力-应变曲线中的扭折）主要是由基体损伤引起的引发。除了SiC材料的特性（例如强度和断裂能）外，还可以观察到RVE尺寸会影响使用计算微力学预测的平均强度和破坏应变。