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

Flax fiber reinforced unsaturated polyester (UP) composite laminates were fabricated by vacuum bagging process and their impact and post-impact responses was 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, respectively. Post impact with incident energy of 25 Joules was employed to occure 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 FE model for the future investigations in the field. The effects of impact and post impact on the failure mechanisms were evaluated using scanning electron microphotography (SEM). Parameters measured were load bearing capability, energy absorption and damage modes. The results show a significant reduction in impact strength after post impact events at all energy levels.