Effect of preload on the impact response of curved composite panels

While in many structures, such as aircraft wings, curved laminates are widely utilized, researchers have mostly focused on flat ones. On the other hand, during their service these panels are under pre-stress which can affect their performance. This study therefore investigated the effect of preloading on the impact response of curved laminates. Low velocity impact tests were conducted on GFRP for three different initial impact energies and pre-loads in two different boundary conditions. The results showed that the damage mode is considerably different in these situations. For example, applying the compressive load on curved laminates, the upper and lower surfaces are under tension and compression stress. The compression stress reduces the propagation of cracks, while in a tension stress field cracks propagate easily. The influence on other impact parameters like maximum force and maximum displacement was also significant.