Modelling of carbon/epoxy sandwich panels with agglomerated cork core subjected to impact loads

Abstract

This work studies the behaviour of sandwich panels made of woven carbon/epoxy face-sheets and agglomerated cork as core material subjected to impacts at intermediate velocities, below the perforation velocity of the panel. Agglomerated cork was selected as an eco-friendly alternative to traditional synthetic polymeric foams. A nonlinear/explicit finite element model was implemented to study the problem. Continuous damage models were used to predict the intra-laminar and inter-laminar damage evolution in the face-sheets. The core behaviour was modelled through a hyperelastic elastomeric foam model with multiaxial failure criteria. The numerical model was validated in two phases. First, the numerical models of face-sheet and core were validated with experimental data from the open literature. Second, the precision of the model of the complete sandwich is assessed with experimental tests carried out in this work.Two cases were studied one when the projectile does not perforate the front face-sheet and another when the projectile does not perforate the back face-sheet. Results show that the numerical model accurately predicts transverse displacements when compared to DIC measurements. Additionally, the model can predict the panel's penetration when comparing with real specimens. Finally, the model provides the damage evolution and the evolution of the different energy absorption mechanisms during the perforation process, something that is not possible to obtain experimentally and provides a valuable tool to understand the phenomenon.