Effect of fiber failure on quasi-static unloading/reloading hysteresis loops of ceramic matrix composites

The two-parameter Weibull model is used to describe the fiber strength distribution. The stress carried by the intact and fracture fibers on the matrix crack plane during unloading/reloading is determined based on the global load sharing criterion. The axial stress distribution of intact fibers upon unloading and reloading is determined based on the mechanisms of fiber sliding relative to matrix in the interface debonded region. The interface debonded length, unloading interface counter slip length, and reloading interface new slip length are obtained by the fracture mechanics approach. The hysteresis loops corresponding to different stresses considering fiber failure are compared with the cases without considering fiber failure. The effects of fiber characteristic strength and fiber Weibull modulus on the fiber failure, the shape, and the area of the hysteresis loops are analyzed. The predicted quasi-static unloading/reloading hysteresis loops agree well with experimental data.