A damage constitutive model for the nonlinear mechanical behavior of C/SiC composites during mechanical cyclical loading/unloading

Abstract

In this study, the nonlinear mechanical behavior and corresponding damage mechanisms of C/SiC composites during cyclic loading/unloading tensile tests were studied. Besides, based on the composite microstructure and damage mechanisms, the damage evolution model and single fiber unit model are proposed to explain the stiffness degradation, inelastic deformation accumulation, and elastic deformation. According to the stiffness degradation law, the damage evolution model based on Weibull failure probability is established, which can fit damage-strain curves well. Additionally, the single fiber unit model considering the microscopic mechanisms of matrix cracking, interfacial debonding, and sliding is established. In the model, the stress distributions before and after loading and unloading are analyzed to obtain the elastic strain and inelastic strain formulas of the composite that can perfectly fit the experimental results (R2 > 99.9%). Because the model reflects the deformation mechanisms of the composites in a much more simplified way, the deformation and damage law of the composite can be well predicted with basic macroscopic parameters such as the composition of the composite, the elastic modulus of the fiber, matrix, and composite, the strength of the matrix and the residual thermal stress of the matrix.