Out-of-plane crushing response of aluminum honeycombs in-situ filled with graphene-reinforced polyurethane foam

Abstract

This work reports the out-of-plane crushing response of aluminum honeycomb (HC) filled with polyurethane (PU) foams. For the filling of the HC, two types of PU foams were manufactured: unreinforced PU (UR/PU) foam and PU foam reinforced (GR/PU) with reduced graphene oxide (rGO) flakes. In this investigation, the static and low velocity impact compressive tests were performed on the separate constituents (UR/PU foam, GR/PU foam and empty HC) and their combinations (UR/PU foam-filled HC and GR/PU foam-filled HC). By the addition of 0.02% rGO flakes, to UR/PU, an increase (over 41%) of the strength and energy absorption properties was obtained. Moreover, due to the interaction effect, the foam-filled HC composite highlights better properties (up to 61%) than the empty HC structure. Further, it has been observed that exposure of the specimens to ultraviolet (UV) radiation do not change the foam density, but their properties increase by up to 30%. Finally, it was noticed that the in-situ foam-filled HC manufacturing technique is clearly superior to the ex-situ method, while the foam material dictates the filled HC collapse mechanisms considerably.