Simplified approach to study oxidative damage of C/SiC composites induced from notch defects

C/SiC composites have been diffusely applied to the preparation of large structural parts, especially in aerospace engineering, due to the high specific strength, high temperature stability and resistance to oxidation. Defects, such as hole, cracks and density defects, are prone to occur in the fabrication process of C/SiC composites, which will lead to premature failure of components during service. Herein, notch defects at different position were prefabricated in C/SiC composites to simulate small cracks and the influence of notch defect on flexural strength and oxidation resistance has been investigated by CT imaging, oxidation test, flexural performance test and microstructural characteristics. The experiment results pointed that the oxidative mass reduction of specimens with distance between notch defect and centerline of 6 mm and 12 mm is more serious than that of distance at 3 mm and 9 mm demonstrating notch defects on the matrix have less impact on the oxidation behavior of the specimens, but the defects on the fibers can seriously reduce the oxidation resistance. Before oxidation, the flexural strength of C/SiC composites increases first and then stabilizes with the increase of notch distance. After oxidation, the flexural strength of C/SiC composites with notch defect at different distance decreases to a certain extent, which indicates that the influence of oxidation on the flexural properties is greater than that of the notch defect itself.