Comparison of cyclic fatigue behavior between C/SiC and SiC/SiC ceramic-matrix composites at elevated temperatures using hysteresis dissipated energy

The fatigue behavior of cross-ply C/SiC and 2D woven SiC/SiC composites at elevated temperatures in air or steam condition have been investigated using the hysteresis dissipated energy. The evolution of fatigue hysteresis dissipated energy and hysteresis dissipated energy-based damage parameter of C/SiC and SiC/SiC composites have been analyzed. For SiC/SiC composite at 1000 °C in steam, the experimental fatigue hysteresis dissipated energy lies in the right part of the fatigue hysteresis dissipated energy versus interface shear stress curve, which indicates that the interface partially debonds during cyclic fatigue loading; however, for C/SiC composite at 800 °C in air, the experimental fatigue hysteresis dissipated energy lies in the right and left part of the fatigue hysteresis dissipated energy versus interface shear stress curve, which indicates that the interface completely debonds upon initial cyclic fatigue loading. By comparing the experimental fatigue hysteresis dissipated energy with theoretical computational values, the interface shear stress of C/SiC and SiC/SiC composites have been estimated. The interface shear stress of C/SiC composite at 800 °C in air decreases much more rapidly than that of SiC/SiC composite at higher temperatures in air or steam condition.