Failure analysis of long-fiber-reinforced ceramic-matrix composites subjected to in-phase thermomechanical and isothermal cyclic loading

Abstract

In this paper, the failure analysis of long-fiber-reinforced ceramic-matrix composites (CMCs) subjected to the in-phase thermomechanical and isothermal cyclic fatigue loading are investigated using the micromechanical approach. The fiber/matrix interface shear stress is determined as a function of testing temperature and material properties, which affects multiple thermomechanical fatigue damage mechanisms of matrix multicracking, fiber/matrix interface debonding and sliding. The Budiansky-Hutchinson-Evans shear lag model is used to determine the micro stress field of the damaged composite. The matrix stochastic cracking model and the fracture mechanics approach are used to determine the matrix crack spacing and fiber/matrix interface debonding/slip length, respectively, considering the temperature-dependent fiber/matrix interface shear stress. The relationships between the testing temperatures, fiber/matrix interface shear stress, fiber/matrix interface debonding and sliding, and the shape, location and area of fatigue hysteresis loops under in-phase thermomechanical and isothermal cyclic loading are established. The effects of fiber volume fraction, fatigue peak stress, matrix cracking space, fiber/matrix interface frictional coefficient and fiber/matrix interface debonded energy and temperature range on the fatigue hysteresis loops under the in-phase thermomechanical and isothermal cyclic loading are analyzed. The fatigue hysteresis loops of unidirectional SiC/CAS and cross-ply SiC/MAS composite subjected to the in-phase thermomechanical and isothermal cyclic loading are predicted.