Damage sequence in thin-and ultra-thin-ply composite laminates under out-of-plane loading

The study of the damage sequence in polymer-based composite laminates during an impact event is a difficult issue. The problem can be even more complex when the plies are thin. This paper investigates experimentally the damage in thin- and ultra-thin-ply laminates under out-of-plane loading for better understanding the damage sequence during impact test. TeXtreme® plain weave plies were used with two different thicknesses, 0.08 mm and 0.16 mm (referenced as ultra-thin-ply and thin-ply, respectively), and tested under different concentrated load levels. Load-displacement curves were analyzed and the extent of damage was inspected using optical microscopy and ultrasonic C-scan technique. The results showed that the damage onset occurs earlier in thin-ply laminates. The damage onset in thin-ply laminates is matrix cracking which induces delaminations, whereas for ultra-thin-ply laminates is due to delaminations which are induced by shear forces and small amount of matrix cracking. Moreover, the fiber breakage appears earlier in ultra-thin-ply laminates. The ultra-thin-ply laminates has smaller delamination area before the fiber breakage. However, after the fiber breakage starts, the delamination area for the ultra-thin-ply laminates is larger.