A Hysteresis Dissipated Energy-Based Parameter For Damage Monitoring Of Carbon Fibre-Reinforced Ceramic-Matrix Composites Under Fatigue Loading

Under fatigue loading of fibre-reinforced ceramic-matrix composites (CMCs), the stress-strain hysteresis loops appear as fibre slipping relative to matrix in the interface de-bonded 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 multi-cracking, fibre/matrix interface de-bonding, interface slipping and interface wear. Based on the fatigue hysteresis theories, the relationship 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 ont eh evolution of the hysteresis dissipated energy and hysteresis dissipated energy-based damage parameter as a function of cycle number have been analysed. 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 day 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 fibre-reinforced CMCs.