Influence of fiber failure on fatigue hysteresis loops of ceramic matrix composites

An analytical methodology has been developed to investigate the influence of fiber failure on fatigue hysteresis loops of ceramic matrix composites in this article. During fatigue loading, matrix cracking, interface debonding and fiber failure occur upon first loading to the fatigue maximum stress. Matrix cracking space and interface debonding length are obtained by matrix statistical cracking model and fracture mechanics interface debonding criterion. Based on the assumption of global load-sharing criterion for the load distribution between the unbroken and broken fibers, an approach to determine fiber failure probability during fatigue loading for the degradation of interface shear stress and fiber strength is developed in this analysis. Upon unloading and subsequent reloading, stress—strain hysteresis loops develop as fiber sliding relative to matrix in the interface debonded region. The unloading interface counter slip length and reloading new slip length are obtained by the fracture mechanics interface debonding criterion. The effects of characteristic fiber strength, fiber Weibull modulus, and fatigue maximum stress on fiber failure during fatigue loading, and then on the shape, location, and area of the fatigue hysteresis loops are investigated. The fatigue hysteresis loops of three different ceramic composites corresponding to different cycles are predicted and agree well with the experimental data.