Modeling matrix multi-fracture in SiC/SiC ceramic-matrix composites at elevated temperatures

Abstract

In this paper, the matrix multi-fracture of SiC/SiC ceramic-matrix composites (CMCs) is investigated using the critical matrix strain energy (CMSE) criterion. The BHE shear-lag model is used to analyze the micro-stress field of the damaged composite, and the fracture mechanics method and the CMSE criterion are adopted to determine the fiber/matrix interface debonded length and matrix multi-fracture density. The temperature-dependent fiber/matrix interface shear stress, Young’s modulus of the matrix, the matrix fracture energy, and the fiber/matrix interface debonded energy are considered in the micro-stress field analysis, fiber/matrix interface debonding criterion, and matrix multi-fracture model. The effects of fiber volume fraction, fiber/matrix interface shear stress, fiber/matrix interface frictional coefficient, fiber/matrix interface debonded energy, matrix fracture energy, and temperature on the matrix multi-fracture of SiC/SiC composite are discussed. When the fiber volume fraction and matrix fracture energy increase, the first matrix cracking stress and matrix saturation cracking stress increase; when the fiber/matrix interface shear stress and interface frictional coefficient increase, the first matrix cracking stress, saturation matrix cracking stress, and saturation matrix cracking density increase with the decrease of the fiber/matrix interface debonded length; when the fiber/matrix interface debonded energy increases, the saturation matrix cracking stress decreases and the saturation matrix cracking density increases due to the decrease of fiber/matrix interface debonding ratio. The experimental matrix multi-fracture and fiber/matrix interface debonding curves of unidirectional SiC/SiC composite at elevated temperatures are predicted. The predicted results agree with experimental data, which proves the efficiency of the developed matrix multi-fracture model.