Mechanical properties and failure mechanisms of three-dimensional stitched C/C-SiC ceramic matrix composites

Revealing the mechanical properties and failure mechanisms of three-dimensional stitched C/C-SiC composites (3DS-C/C-SiCs) is crucial for ensuring their safety and reliability during service. Here, we report the mechanical behaviors and failure mechanisms of 3DS-C/C-SiCs. The failure mechanisms were investigated with the ultradepth-of-field microscope and scanning electron microscope. The mechanical behaviors of two-dimensional laminated C/C-SiC composites (2DL-C/C-SiCs) were analyzed for comparison. Moreover, the effect of pores on the tensile properties and failure mechanisms of 3DS-C/C-SiCs was explored through finite element analysis. The results indicate that the compressive and shear properties of 3DS-C/C-SiCs are improved compared to 2DL-C/CSiCs, while there is a reduction in tensile and flexural properties. The overall fracture energy of the materials is improved. The introduction of stitching yarn (SY) suppresses crack generation and extension along the delamination direction but produces more defects around it, such as fiber buckling and breakage. The failure modes of the materials are matrix cracking, fiber fracture, and delamination failure. The finite element results reveal that tensile strength and modulus decrease with increasing porosity. The finite element model with a 15 % volume content of pore defects (VP) accurately predicts the tensile properties and failure mechanisms of 3DS-C/C-SiCs.