Thermal-mechanical-oxidation coupled first matrix cracking stress model for fiber reinforced ceramic-matrix composites

In this work, we research the combined influence of residual thermal stress, interface debonding and oxidation, and temperature on first matrix cracking stress of fiber reinforced ceramic-matrix composites (FRCMCs). Based on the shear-lag theory, the axial stress distribution of matrix and fiber considering interface oxidation and residual thermal stress is given, and we propose a criterion for interface debonding. Then, a thermal-mechanical-oxidation coupled first matrix cracking stress model is proposed for FRCMCs, according to energy balance approach. Reasonable agreement is obtained between the model predictions and available experimental results of SiCf/RBSN and SiCf/SiC composites. Moreover, the effects of some key material parameters and oxidation time on first matrix cracking stress are analyzed quantitatively by the model. This research offers a quantitative tool for evaluating and predicting the matrix cracking behavior of FRCMCs under thermal-mechanical-oxidation coupled environment.