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

Under fatigue loading of fiber-reinforced ceramic-matrix composites (CMCs), 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, which can reveal the fatigue damage mechanisms, i.e., matrix multicracking, fiber/matrix interface debonding, interface slipping and interface wear. Based on the fatigue hysteresis theories, the relationships between hysteresis dissipated energy, hysteresis dissipated energy-based damage parameter, stress strain hysteresis loops, and fatigue damage mechanisms have been established. The effects of fiber volume content, fatigue peak stress, fatigue stress ratio and matrix crack spacing on the evolution of the hysteresis dissipated energy and hysteresis dissipated energy-based damage parameter as a function of cycle number have been analyzed. The experimental hysteresis dissipated energy and hysteresis dissipated energy-based damage parameter of unidirectional CMCs corresponding to different fatigue peak stresses and cycle numbers have been predicted using the present analysis. It was found that the hysteresis energy-based parameter can be used to monitor the fatigue damage evolution and predict the fatigue life of fiber-reinforced CMCs. (C) 2015 Elsevier B.V. All rights reserved.