Experimental and numerical assessment of the impact behaviour of a composite sandwich panel with a polymeric honeycomb core

The capability to guarantee passenger safety is a core feature of any transportation system. For this reason, a considerable effort is being committed, by researchers, to the study of innovative shock-absorbing devices able to increase the safety performance. According to this topic of great interest, this paper presents a numerical/ experimental study on a new effective shock absorber concept achievable by means of the Additive Manufacturing technology.Indeed, additive technologies exhibit some fundamental advantages, such as the possibility to produce com-plex microstructures, with superior impact energy absorption capabilities, which cannot be made with standard manufacturing processes. Hence, this manufacturing technique could be preferred for the development of high -efficiency shock absorbers cores. In the present work, to achieve shock absorbers high mechanical efficiency while limiting mass and volume, an innovative sandwich shock absorber concept is introduced, which uses additive manufactured solutions for the core by combining the advantages offered by thermoplastics (poly-propylene), such as their ability to absorb energy through plasticisation and their recyclability, to those offered by fibre-reinforced thermoset composites (Carbon Fibre Reinforced Polymers), i.e. high stiffness/mass and strength/mass factors.First, numerical low-velocity impact analyses have been carried out to compare the mechanical response of several shock absorber configurations, Designed for Additive Manufacturing (DfAM), characterised by a poly-propylene (PP) honeycomb core and CFRP composite external skins. These PP-CFRP sandwich configurations have been compared to full polypropylene configurations (with polypropylene skins and core PP-PP). Compar-isons have shown that the PP-CFRP configurations are characterised by better overall crashworthiness perfor-mances (energy absorption and peak-force smoothing). Finally, an experimental activity, including ASTM D7136 based impact tests, have been carried out on the best performing investigated PP-CFRP configuration, to pre-liminary validate the numerical results.