A hysteresis dissipated energy-based damage parameter for life prediction of carbon fiber-reinforced ceramic-matrix composites under fatigue loading

Abstract

Under fatigue loading, the stress–strain hysteresis loops appear as fiber slipping relative to matrix in the interface debonded region. The area of hysteresis loops, i.e., the hysteresis dissipated energy, changes with the increase of cycle number, and can reveal fatigue damage mechanisms, i.e., matrix multicracking, fiber/matrix interface debonding, interface slipping, interface wear, and fibers fracture. Based on the fatigue hysteresis theories considering fibers failure, the hysteresis dissipated energy and a hysteresis dissipated energy-based damage parameter changing with the increase of cycle number have been investigated. The relationships between the hysteresis dissipated energy, hysteresis dissipated energy-based damage parameter, stress–strain hysteresis loops, and fatigue damage mechanisms have been established. The effects of fatigue peak stress, stress ratio, matrix crack spacing and fiber volume content on the evolution of hysteresis dissipated energy and hysteresis dissipated energy-based damage parameter as a function of cycle number have been analyzed. It was found that the hysteresis dissipated energy-based damage parameter is much more sensitive to interface debonding and interface frictional slipping compared with the hysteresis dissipated energy under fatigue loading, and can be used to reveal the fatigue damage evolution and predict the fatigue life of fiber-reinforced CMCs. The experimental fatigue life S–N curves of unidirectional CMCs have been predicted using the present analysis.