Theoretical approach to predict transverse impact response of variable-stiffness curved composite plates

This research studies the low velocity impact behaviour of variable stiffness curved composite plates. Since variable thickness within composite structures is recognised as an important factor on the performance of the structures, significant mathematical modelling to predict the impact response of these types of structure is essential. Varying thicknesses of sections is widely found in aerospace and automotive composite sub structures. It has been observed that changing of geometry of these sections can vary the dynamic response of anisotropic composite structures under a range of monolithic and dynamic loading conditions. Here we have used first order shear deformation theory to predict the contact force history of curved composite plates and the same approach was used for variable thickness composite plates, which provides the main novelty of this research. It was shown that the model developed here is capable of successfully predicting the response of variable stiffness composite plates with a range of layups and geometry designs under impact loading conditions

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