Stress-Rupture of Fiber-Reinforced Ceramic-Matrix Composites with Stochastic Loading at Intermediate Temperatures. Part I: Theoretical Analysis

Under stress-rupture loading, stochastic loading affects the internal damage evolution and lifetime of fiber-reinforced ceramic-matrix composites (CMCs) at intermediate temperatures. The damage mechanisms of the matrix cracking, fiber/matrix interface debonding and oxidation, and fiber fracture are considered in the analysis of stochastic loading. The strain, fiber/matrix interface debonding and oxidation length, and the broken fibers fraction versus the time curves of SiC/SiC composite under constant and three different stochastic loading conditions are analyzed. The effects of the stochastic loading stress level, stochastic loading time, and time spacing on the damage evolution and lifetime of SiC/SiC composite are discussed. When the stochastic loading stress level increases, the stress-rupture lifetime decreases, and the time for the interface complete debonding and oxidation decreases. When the stochastic loading time and time spacing increase, the stress-rupture lifetime decreases, and the time for the interface complete debonding and oxidation remains the same.