High-velocity impact behaviors and post-impact tension performance of 2D-C/SiC composite beams

Abstract 2D-C/SiC composites have widely been used in aeronautical aerospace engineering, but their mechanical behaviors under small-mass and high-speed impact have not been thoroughly studied yet. In this paper, 2D-C/SiC beam specimens were impacted by a single stage light gas gun and the fracture processes were captured by a high-speed camera. Post-impact internal and surface damage morphologies were scanned by CT and SEM respectively. Similar damage modes were revealed by high-speed images. Subsequently, quasi-static post-impact tension tests were conducted to understand the residual mechanical properties. Acoustic emission (AE) signals of specimens were detected during the tests and then classified by the K-means algorithms. Therefore, evolutions of matrix damage, interfacial delamination and fiber fracture were recognized. At the same time, strain value was obtained by digital image correlation (DIC) method and main crack propagations were obvious in strain contours. A combination of the AE and DIC methods very well monitored the real-time damage during post-impact testing, which further revealed the damage during impact phase.