Impact behavior of sandwich structures made of flax/epoxy face sheets and agglomerated cork

The unremitting quest of natural and renewable materials able to replace their synthetic counterparts in high-performance applications has involved also sandwich structures. In this regard, the aim of this work is to characterize the impact response, in both high- and low-velocity conditions, of green sandwich structures made of agglomerated cork as core and flax/epoxy laminates as face sheets. Both bare cork, flax skins, and complete sandwich structures were subjected to impacts at three different energy levels representing the 25%, 50%, and 75% of the respective perforation thresholds. A gas gun was instead used to assess the high-velocity impact behavior of these green sandwich structures and evaluate their ballistic limit. This study shows that the buckling of cell walls of agglomerated cork enables to tailor the damage extension through-the-thickness in low-velocity impacts compared to traditional synthetic foams coupled with a considerable amount of energy absorption.