Pore evolution and mechanical response under locally varying density defects in ceramic matrix composites

Ceramic matrix composites have garnered significant attention in aerospace and other fields due to their outstanding properties. However, as a common and critical defect, density defect often results in non-uniform matrix distribution and internal pore formation, posing a substantial risk to component safety. This paper presents a novel method aimed at deliberately inducing varying degrees of density defects in SiC_f/SiC. The feasibility of this method is validated using infrared thermography and computed tomography. As density defects aggravate, the porosity of the sample's defective region gradually increases, with both the number of micropores and the dimensions of larger pores expanding. This trend underscores the decreased compactness of the SiC matrix. Additionally, there is an initial decline in tensile strength followed by stabilization, while the tensile elastic modulus exhibits a continued decrease. The retention rates of the minimum tensile strength and tensile elastic modulus are 83.89 % and 64.77 %, respectively, compared to those of the defect-free samples. In terms of compressive properties, both compressive strength and compressive elastic modulus exhibit progressive decreases, culminating in final retention rates of 76.54 % and 72.02 %, respectively. Density defects reduce the matrix cracking stress and introduce new defects such as delamination, thereby altering the material's damage mechanism. This study provides innovative perspectives for risk assessment and lifespan prediction of density defects, especially concerning more complex components like turbine blades.