Flexural property and failure mechanism of C/SiC composites investigated by high-temperature three-point bending and in-situ X-ray computed tomography

C/SiC composites with complex microstructures exhibit intricate damage and failure mechanisms. To address the limitations of traditional ex-situ characterization methods in revealing the internal damage mechanism, this work proposes a high-temperature in-situ bending test using X-ray computed tomography. The results of three-point bending tests on C/SiC composites verify the rationality of the proposed method. We find that the bending strength and modulus of C/SiC composites increase at 900°C and decrease at 1100°C. An in-situ flexural experiment of C/SiC composite at 900°C is conducted. The X-ray data indicate that microcracks nucleate within the matrix surrounding defects, and with increasing load, stress concentration promotes their further propagation, ultimately penetrating the fiber bundles. Finally, the fracture surfaces of the specimens were analyzed by SEM, the bending failure modes at different temperatures were identified, and the intrinsic mechanisms for the changes in bending strength and modulus were revealed.