A micromechanical tension-compression fatigue hysteresis loops model of fiber-reinforced ceramic-matrix composites

In this paper, a micromechanical tension-compression fatigue hysteresis loops model of fiber-reinforced ceramic matrix composites (CMCs) is developed. Upon unloading or reloading, the stress-strain of tension-compression fatigue hysteresis loops are divided into three different regions. Multiple micromechanical damage parameters of unloading transition stress, closure stress of the matrix cracking, compressive transition stress, complete compressive stress, and reloading transition stress are adopted to characterize the tension-compression stress strain hysteresis loops. The characteristics of the tension-compression fatigue hysteresis loops of unidirectional SiC/CAS composite are analyzed for different material properties, damage stage, tensile fatigue peak stress, and compression fatigue valley stress. The experimental tension-tension and tension-compression fatigue stress-strain hysteresis loops of unidirectional SiC/CAS composite are predicted using the developed micromechanical models. Under low fatigue valley compressive stress, the tension-compression fatigue hysteresis loop exhibits no closure of matrix cracking; and under high fatigue valley compressive stress, the tension-compression fatigue hysteresis loops exhibit closure of matrix cracking, and complete compressive in the fiber and the matrix. However, the compressive valley stress has no effect on the values of matrix cracking closure stress, compressive transition stress, and complete compressive stress.