Stress rupture of fiber-reinforced ceramic-matrix composites subjected to different stochastic loading spectrums at intermediate temperatures

Abstract

In this paper, stress rupture of fiber-reinforced ceramic-matrix composites (CMCs) subjected to different stochastic loading spectrums at intermediate temperatures (600 to 1000 °C) is investigated. Under stress rupture at stress level higher than the first matrix cracking stress, multiple damage mechanisms of matrix cracking, fiber/matrix interface debonding, interphase and fiber oxidation, and fiber fracture are considered to analyze evolution of composite strain. Four different stochastic loading spectrums are considered in the analysis of damage evolution and lifetime of fiber-reinforced CMCs under stress rupture loading. Relationships between stochastic loading stress, frequency, time, interface debonding and oxidation length, fiber failure probability, and stress rupture lifetime are established. Effects of stochastic loading stress and time, fiber volume, matrix crack spacing, interface debonding energy, interface shear stress, and temperature on composite strain, interface debonding and oxidation length, and the fiber failure probability versus time are analyzed. Experimental stress rupture strain and lifetime of SiC/SiC composite under constant stress and stochastic loading spectrums are predicted. When the stochastic loading stress, frequency, and temperature increase, the stress rupture lifetime and the time for the interface complete debonding and oxidation all decrease.