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.