The imperfection sensitivity of trapezoid origami crash boxes

Diamond and trapezoid origami crash boxes (DOCBs and TOCBs, respectively) have attracted widespread attention due to their favorable mechanical properties. It has been confirmed that geometric imperfections significantly affect the crashworthiness of DOCBs. To explore the impact of imperfections on the crashworthiness of TOCBs, the TOCB profile was globally scanned, and the imperfections were characterized. It was verified that point and surface imperfections were the two main geometric imperfections. Based on the theoretical analysis of the deformation process of the TOCB, the imperfection-sensitivity mechanism was revealed. The experimental and numerical results validated that the point imperfections ratio (Ai /t, defined as the ratio between the point imperfections Ai in TOCB and the box thickness t) at the crease intersections were the main reason for the change in the TOCB deformation process, while the surface imperfections ρ affected the initial peak force. Numerical models with imperfections were established to compare the crashworthiness of the TOCB and DOCB with the same imperfections. When the surface imperfections ρ ≤ 0.12 and point imperfection ratio Ai/t ≤ 3.0, the average crushing force Fave of the TOCB decreased by 4.7 % and increased by 3.4 %, respectively. Correspondingly, those of the DOCB decreased by 5.7 % or 19.4 %, respectively; thus, the TOCB had a much lower imperfection sensitivity than the DOCB.