Effect of matrix sub-layer interfacial fracture on residual strength improvement of the fatigued carbon/carbon composites

In the present study, flexural behavior of carbon fiber reinforced pyrolytic carbon matrix composites (C/C composites) before and after fatigue tests had been studied. The results showed that the residual flexural strengths of the samples had been improved after fatigue tests, and the fracture mechanisms of the original and post-fatigue specimens had some differences. Fracture mechanism of the original specimens could be described as fiber/matrix interfacial de-bonding, and the dominant damage of the post-fatigue specimens could be regarded as pyrolytic carbon sub-layers' step-delamination. The degradation of matrix sub-layer interfacial bonding strength was beneficial to improve the mechanical properties of C/C composites.