Response of pre-loaded laminate composite plates subject to high velocity impact

An experimental and analytical study of two cases of static preload (uniaxial and biaxial) was made to determine the response of structural plate elements subjected to high velocity impacts under in-plane tensile preloading conditions. The results were compared with those obtained in non-preloading specimens. Rectangular specimens were used for the uniaxial and non-preload tests, while cross-shaped specimens were used for the biaxial tests. The impacts were made by spherical projectiles travelling at velocities from 140 to 525 m/s. As a general result, the existence of a static preloading on the specimen was found to affect the ballistic limit and the damaged area. The biaxial preload specimens showed the higher ballistic limit and the damaged area was slightly bigger in the non-preloaded specimens. From the analytical model, the ballistic limit calculated for the non-loaded specimens showed a difference of 16% from the experimental values, and in the preloaded specimens the model did not show showed the same tendency as that observed experimentally.