Ricerc@Sapienza

Thanks to the unique flexural properties, sandwich composites are considered as irreplaceable structures in many industrial fields, but their susceptibility to impact events is still a considerable drawback that undermines their structural integrity determining a reduction of their load-bearing capabilities. Considering that the core material plays the major role to distance the skins, the knowledge of its multiple-impacts response becomes a key design parameter in order to ensure a long-term stability to the structure.

Considering the major role played by sandwich structures in many fields where high stiness-to-weight ratio is required, the selection of a suitable core material is of paramount importance. In order to face the environmental problems related to waste disposal, the selection of an eco-friendly core material is now included in the design criteria of sandwich structures. Agglomerated cork is recognized as a good solution that combines satisfactory mechanical performances and eco-sustainability.

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.

In this work, experimental compression tests have been performed on parallelepiped specimens cut from an agglomerated cork
slab. The tests have been performed both using a quasi-static testing machine and a polymeric Split Hopkinson Bar, in order to
assess the sensitivity of the material to the strain rate. A standard and a high-speed digital camera have been used to collect frames
of the samples during the tests. 2D DIC analyses have been conducted on the pictures of lateral faces of the specimens in order to