Finite Element Modelling of 3D Braided Ceramic Matrix Composites

초록

Ceramic matrix composites (CMCs) have been widely applied in industries due to some extraordinary mechanical properties, such as high specific strength and extreme thermal shock resistance. However, the mechanical property characterization of CMC has become more challenging because of the complicated 3D braided architecture. Even though some classical models have been developed to predict the mechanical performance of 3D braided CMC, applications of these models have been limited due to CMC different braided angle, yarn directions, and the internal architecture. For laminated materials, fiber breakage, squeeze, interfacial debonding between fiber and matrix, and matrix crack may occur easily, all of which propagate rapidly. Thus, the microscopic structural defect would directly result in macroscopic material failure. In this study, a generalized finite element model based on multi-scale (including micro-, meso-, and macro-scales) structure of 3D braided CMC is developed to analyze its effective material properties. In micro-scale, basic unit elements (matrix element, yarn element, and mixed interface element) are built to compose the typical unit cell (RUC) model of CMC. In mesoscale, some RUC are used to build the representative volume element (RVE) of CMC based on the braided angle, yarn directions, and the internal architecture. In macro-scale, micro- and meso-scale models are implemented into the macroscopic model to predict the constitutive material properties of CMC by homogenization technique. Based on the above asymptotic multi-scale finite element method, taking the complicated microscopic architecture of CMC into consideration, the mesoscopic local stress distribution, as well as the macroscopic constitutive material stiffness, is predicted through a commercial finite element software. The generalized finite element method presented in this research can be used for the material strength prediction of CMC. Moreover, it can be also applied for the multisc