Numerical modelling of graded foam based sandwich structures subjected to impact

This article describes the low velocity impact response of sandwich structures based on layered cores fabricated by bonding foams with different densities and carbon fiber skins together, investigated both experimentally and numerically. The impact behaviour of the panels was characterized by recording the resulted load-displacement traces and by determining the energy required to perforate the target. The impact response of the graded sandwich structures was modelled using finite element analysis package Abaqus/Explicit. The CFRP skins were modelled as an orthotropic elastic material before failure, and the subsequent damage processes were predicted using Hashin's failure criteria. The PVC foam cores were modelled using crushable foam model with hardening plasticity. The resin at the interface between the CFRP skin and the PVC foam was modelled using the cohesive elements. The predicted load-displacement responses and failure modes are compared with test results, with good agreement. It has been shown that graded core sandwich structures can out-perform their monolithic counterparts in terms of their impact perforation resistance. It has also been observed that placing higher density foam core against the top surface skin, placing the lowest density foam in the centre of the core and a ductile foam against the lower surface can lead to an improved perforation resistance.