Graphite/epoxy foam sandwich panels under quasi-static indentation

This study investigates the force-indentation response of sandwich panels subjected to a rigid spherical indentor. The sandwich panels are made of graphite/epoxy face sheets with a polymethacrylimide foam core. A three-dimensional analytical solution method is developed to determine the complete stress and displacement fields in a sandwich panel, as well as the contact pressure arising fi om static indentation by a rigid sphere. Unlike the usual assumption of a Hertzian-type contact pressure distribution, the sphere's unknown contact area and pressure distribution due to indentation are obtained as part of the solution by utilizing an iterative solution method leading to the contact force-indentation relation. Analytical predictions are validated by performing quasi-static indentation experiments. (C) 2000 Elsevier Science Ltd. All rights reserved.