Curved Crease Tube Structures as an Energy Absorbing Crash Box

Straight-crease origami crash boxes have previously been designed to possess a near optimum failure mode for a tubular energy-absorbing device. This failure mode, termed a ‘complete diamond mode’ (CDM), possesses a low peak force P_max and high average force P_avg, caused by generation of travelling hinge lines that propagate laterally during crushing. The present study investigates the hypothesis that a curved crease structure could further improve failure characteristics by having a lower P_max due to the initially curved corner lobes. An experimental and numerical investigation was conducted using aluminium curved crease origami tubes, with certain curved crease tubes exhibiting the desired CDM and good correspondence seen between experimental and numerical behaviours. A parametric numerical analysis on 45 steel curved crease origami tubes showed a maximum reduction in P_max of 67% was observed, which is better than the straight-crease origami crash boxes in this respect. A maximum increase in P_avg of 65% was observed, which is worse than straight-crease origami crash boxes. A lower P_max was thus achieved as hypothesised, however this improvement came at the expense of a reduction in average force. Curved crease crash boxes are therefore concluded to have minimal benefit over existing straight crease crash box designs.