Stress and strain measurements in carbon-related materials impacted by a high-velocity steel sphere

To investigate the behavior of carbon-related materials damaged by the impact of a sphere, stress and strain measurements during the impact were carried out using a PVDF stress gauge and a constantan strain gauge. A spherical projectile having a velocity of ca. 150–1300 m/s was allowed to impact carbon fiber-reinforced plastics (CFRPs) with different carbon fibers, CFRPs with and without surface-treated fibers, polycrystalline graphites and a C/C composite. The maximum stress generated in the CFRPs depended on the reinforcing fibers; pitch-based fiber resulted in larger increase in stress with impact velocity. The CFRP without the surface-treated fiber resulted in lower strain and stress than the CFRP consisting of the surface-treated fiber. Polycrystalline graphites showed a very large strain, and then powdering; the movement of the powder was considered to affect stress and strain in the graphite materials.