Experimental Study on Low-velocity Impact and Residual Strength of SiC/SiC Composite Laminates

Low-velocity impact is an inevitable problem in the service of ceramic matrix composites structures in high speed aircraft. Therefore, the damage type and residual bearing capacity after low-velocity impact are critical factors for ensuring the safety of the aircraft structures. In this study, two-dimensional braided SiC/SiC composite laminates were taken as the research objects, and low-speed impact tests under different energies were carried out. The damage morphology of SiC/SiC composites was observed by computed tomography, and the damage mechanism of SiC/SiC composites during the impact process was revealed by analyzing the load history curve and strain history curve. Post-impact residual strength tests were carried out on specimens with barely visible damage and the effect of barely visible damage on the residual strength of SiC/SiC composites was investigated. The results showed that under low-velocity impact load, surface damage of specimens mainly included no surface damage, barely visible damage, semi-penetrating damage and penetrating damage. Internal damage of specimens mainly included cone cracks, yarn breakage and delamination. The residual properties of SiC/SiC composites were found to be severely affected by low velocity impact damage. The residual compressive strength of the specimen with barely visible damage was 81% of that of the undamaged specimens, and the residual tensile strength was only 68% of that of the undamaged specimens.