SiC/SiC复合材料层板低速冲击及其剩余强度试验研究

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

高速飞行器中的陶瓷基复合材料结构在服役过程中不可避免地会遇到低速冲击问题,低速冲击后的损伤形式以及剩余承载能力是影响飞行器结构安全的关键问题。本研究以二维编织SiC/SiC复合材料板件为研究对象,在不同能量下开展了低速冲击试验,分析了低速冲击载荷下试验件的表面损伤状态,通过计算机断层扫描技术观察了试验件内部的损伤形貌,结合冲击过程中的冲击响应曲线以及应变历史曲线,分析了SiC/SiC复合材料低速冲击过程的损伤机理。针对含勉强目视可见损伤的试验件开展了冲击后剩余强度试验,研究了勉强目视可见损伤对SiC/SiC复合材料剩余承载性能的影响。结果表明,在低速冲击载荷的作用下,试验件的表面损伤主要包括无表面损伤、勉强目视可见损伤、半穿透损伤以及穿透损伤,试验件的内部损伤主要有锥形体裂纹、纱线断裂以及分层损伤。低速冲击损伤会严重影响SiC/SiC复合材料的剩余性能,虽然试验件损伤勉强目视可见,但其剩余压缩强度为无损件81%,剩余拉伸强度仅为无损件的68%。

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.