Micromechanical modeling of loading rate–dependent tensile damage and fracture behavior in fiber-reinforced ceramic-matrix composites

Abstract

In this paper, the loading rate–dependent tensile damage and fracture behavior of fiber-reinforced ceramic-matrix composites (CMCs) are investigated. A micromechanical tensile constitutive model is developed considering multiple tensile damage mechanisms. A new parameter of the interface debonding rate is proposed to characterize the strain rate–dependent tensile damage evolution in fiber-reinforced CMCs. Experimental tensile stress-strain curves, composite’s tangent modulus, interface debonding ratio, and probability of fiber’s breakage in unidirectional SiC/CAS-II, 2D plain-woven CVI C/SiC and SiC/SiC, 2.5D woven CVI C/SiC, and 3D woven CVI and PIP SiC/SiC composites are predicted for different strain rates at room and elevated temperatures. Effects of fiber’s preforms, testing temperature, and fabrication method on the loading rate–dependent tensile damage and fracture behavior of fiber-reinforced CMCs are analyzed. Relationships between composite’s microstructure, mechanical behavior, and strain rate for different CMCs are established. The rate of interface debonding increased with increasing strain rate and was the highest for unidirectional SiC/CAS-II, and the lowest for 3D woven SiC/SiC, and the rate of interface debonding was independent of testing temperature. For unidirectional SiC/CAS-II and 2D plain-woven CVI SiC/SiC composites, when the loading rate increased, the proportional limit stress, tensile strength, and fracture strain increased; and, for 2.5D woven CVI C/SiC and 3D woven CVI SiC/SiC, when the loading rate increased, the proportional limit stress, composite tensile strength, and fracture strain decreased.