Abstract
This study aims to investigate the high-speed impact response, specifically the delamination behavior, of CFRP laminates utilized extensively in aerospace applications. The evaluation of Compression After Impact (CAI) strength, which defines the structural design limit for composite structures, typically relies on conventional low-velocity impact tests (~10 m/s). However, actual high-speed events like bird strikes involve velocities exceeding 250 m/s. We employed a detonation-driven high-speed gas gun to conduct impact tests on CFRP laminates while maintaining a constant kinetic energy of approximately 10 J. By utilizing four different projectile materials (PP, POM, Al, SUS), we achieved a broad velocity range from ~1100 m/s (PP) to ~390 m/s (SUS). Dynamic Mechanical Analysis (DMA) confirmed the viscoelasticity of CFRP, suggesting modulus values around 28.5 GPa across the tested high-speed range. Contrary to expectations based solely on CFRP viscoelasticity, soft X-ray observation of internal damage revealed that the lowest velocity (highest density) projectile, SUS, caused the largest delamination area per unit energy, while high-velocity PP and POM projectiles caused the smallest damage. This phenomenon is primarily attributed to the significant proportion of kinetic energy consumed by the internal energy conversion (melting and deformation) of the low-density polymer projectiles (PP, POM) upon high-speed impact. These findings highlight that the projectile's physical properties critically influence energy transmission and damage assessment in the high-speed impact regime.
