Damage and failure mechanisms of PIP-C/SiC composite T-beams considering structural features of the triangular region

The extreme aerothermal environment encountered by hypersonic vehicles during operation presents significant challenges for structural design. Carbon fiber-reinforced silicon carbide (C/SiC) materials, with their outstanding performance in high-temperature conditions, are well-suited for high-temperature structural applications in such vehicles. Although C/SiC composite T-beams are widely employed in hot structures, their failure mechanisms remain poorly understood. This study investigates the typical failure behavior and damage evolution of PIP-fabricated plain-woven C/SiC composite T-beams under pull-off loading through combined experimental and numerical analyses. Experimental results indicate that under pull-off loading, the ultimate load of the C/SiC composite T‑beam structure is 1.91 kN. The dominant failure mode is delamination in the triangular region. The failure is attributed to matrix failure caused by the weak interlaminar properties of the composite. Surface strain evolution during loading was captured using digital image correlation (DIC), and post-test CT scanning and SEM were employed to characterize internal damage and fracture morphology. A progressive damage model integrating a strain-based 3D Hashin criterion and a cohesive zone model was developed to simulate the damage process. The simulation revealed the internal delamination propagation through the thickness direction, which is inaccessible to surface observation, and provided the stress distribution driving the delamination. This study provides a basis for evaluating the performance of C/SiC composite T-beam structures.