Dynamic crushing and energy absorption of foam filled multi-layer folded structures: Experimental and numerical study

Abstract

Crushing behaviours of foam filled multi-layer truncated square pyramid (TSP) kirigami structures are studied experimentally and numerically in this study. Each layer of this TSP foldcore is folded using a single aluminium sheet with pre-cuts. Light weight foams are inserted into each unit cell of the TSP foldcore to enhance its loading and energy absorption capacity. The effects of the foam material, density and shapes of foam material on crushing resistance of the multi-layer folded structure are studied. Two foam materials, i.e. expanded polystyrene (EPS) foam with density of 13.5, 19 and 28 kg/m3; rigid polyurethane (PU) foam with density of 35 kg/m3 are used as foam infill for this multi-layer foldcore. Two shapes of PU foam infill are studied as well. Single layered TSP foldcores with foam infill are firstly studied under quasi-static crushing condition, then foam filled multi-layer TSP foldcores are crushed under dynamic loading conditions. Numerical models are verified with the experimental results, followed by intensive numerical simulations. Key parameters such as peak and average crushing resistance, densification strain and specific energy absorption are compared among the foldcores with different foam configurations. Comparing with other cellular structures, uniform collapsing of the proposed foldcore is observed under both quasi-static and dynamic loading conditions with the uniformity ratio ranging between 1.1 and 2.0. Significant increases in average crushing resistances ranging from 36.6% to 82% are also observed by adding foam fillers, while the mass only increases by 3.2% to 20.4%.