The response of composite structures with pre-stress subject to low velocity impact damage

The effect of an initial pre-stress on the response of carbon-fibre/epoxy laminated plates subjected to low velocity impact is investigated. Prior to being impacted, the samples are loaded either uniaxially or biaxially using a specially designed test rig which enables tension or compression loading, independent on each axis. Impact tests were carried out for two impact energies for uniaxial and biaxial tension, pure shear and the zero pre-stress cases. The effect of the pre-stress on the permanent indentation depth, absorbed energy and peak impact loads is experimentally quantified. The results indicate that the penetration/perforation depth, peak load and absorbed energy are essentially independent of the nature and magnitude of the pre-stress at low levels of impact energy (6 J), becoming more significant at higher levels of impact energy (10 J). (C) 2004 Elsevier Ltd. All rights reserved.