Axial and lateral crushing responses of aluminum honeycombs filled with EPP foam

This paper aimed to experimentally understand the effects of Expanded Polypropylene (EPP) foam filling on the mechanical properties of aluminum (Al) honeycomb panels. The process of lightweight EPP foam with different densities filling in Al honeycomb composites was first studied, then a series of axial (out of-plane) and lateral (in-plane) compression tests were carried out on the bare and filled honeycombs. It is showed that the peak strength, mean crushing strength and total energy absorption (EA) in the axial tests increased with foam filler (increased by approximately 2.310-43.069%, 34.791-120.219% and 46.765-179.474% with respect to bare honeycomb, respectively); and the higher foam density, the greater filling effect, whereas the specific energy absorption (SEA) remained unchanged with increase in the foam density. Interestingly, more significant improvement in total energy absorption and SEA were found under lateral crushing. All the foam filled panels were of even greater energy absorption than the sum of bare honeycomb and EPP foam separately under both axial and lateral crushing. The foam filler had no significant effect on its deformation pattern under axial crushing, whereas it helped decrease local densification in honeycomb, leading the filled panels to deform in uniform rhombus shapes under lateral crushing. (C) 2017 Elsevier Ltd. All rights reserved.