Effect of damage on the energy absorption of prismatic thin-walled polymer composite structures

This paper investigates the effect of three types of simulated damage on the specific energy absorption,(SEA) under axial crushing of square section E-glass/polyester composite tubes. Damage was simulated by through-drilled holes of various sizes, by delaminations of different sizes and by zones of out-of-plane impact damage created using a hemispherical tup driven at different energy levels. Also, in order to increase tolerance to out-of-plane impact damage, a thermoplastic interleaf was moulded into a number of samples. Tube samples were crushed axially at quasi-static (5mm/min) and impact (5ms(-1)) rates. SEA was seen to be strongly influenced by loading rate and significant reductions in SEA were seen as rate increased. Below a certain threshold damage level (or size) there was no effect on the SEA. Above this threshold, the damage triggered unstable failure - leading to greatly reduced energy absorption capability. The threshold level-was seen to be dependent on damage type, damage level and test rate and a significant improvement in damage tolerance was seen as the loading rate increased. The SEA for thermoplastic interleaf samples was reduced, but became independent of rate.