Delaminations of barely visible impact damage in CFRP laminates

Abstract

CFRP laminates were impacted by projectiles of low masses, accelerated in an air gun, to have barely visible impact damage (BVID) to simulate damage to aircraft by runway debris. The delamination damage on individual interfaces was revealed by the destructive method of thin strips. In sub-BVID and BVID specimens, the damage was confined mostly to the front 30% of the laminate thickness. Delamination areas in the BVID specimens were found to be considerable — the largest dimension exceeding 12 mm on several interfaces. Nucleation of delamination damage was observed in interfaces adjacent to the mid plane in BVID specimens. At higher impact energies, about 110 to 150% more, the delamination damage was observed on almost all the interfaces with no sign of spalling at the rear surfaces. In comparison with a lightweight projectile of aluminium (4·4 g), a higher density steel projectile (11·8 g) caused more delamination damage for the same impact energy and an identical geometry of projectiles.