The post-impact response of flax/UP composite laminates under low velocity impact loading

Flax fibre-reinforced unsaturated polyester composite laminates were fabricated by vacuum bagging process and their impact and post-impact responses were investigated through experimental testing and finite element simulations. Samples of 60 mm x 60 mm x 6.2 mm were cut from the composite laminates and were subjected to a low-velocity impact loading to near perforation using hemispherical steel impactor at three different energy levels, 25, 27 and 29 Joules. Post-impact was employed to obtain full penetration. The impacted composite plates were modelled with various lay-ups using finite element software LS-DYNA (LS-DYNA User's Manual 1997) to provide a validated finite element model for the future investigation in the field. The effects of impact and post-impact on the failure mechanisms were evaluated using scanning electron microscopy. Parameters measured were load bearing capability, energy absorption and damage modes. The results indicate that both peak load and the energy absorption were reduced significantly after the post-impact events. Consequently, it was observed from the visual images of the damages sites that the extent of damage increased with increased incident energy and post-impact events.