Energy absorption of thin-walled square tubes designed by kirigami approach

Thin-walled tubes are extensively employed as energy absorption devices. The extensional mode (EM) of collapse in thin-walled square tube is desirable in terms of energy absorption while facing impact loading. In this paper, a novel tube known as the kirigami crash box (KCB) that is designed by kirigami approach, is proposed to improve the crashworthiness of the tubular structures by collapsing in EM. The experimental and numerical results show that kirigami pattern in KCB serves as both geometric imperfection to reduce the initial peak force F-max and mode inducer to trigger the desired EM while collapsing. Numerical simulation indicates that the ideal EM is successfully triggered with a 39.7% reduction of initial peak force F-max and 33.9% increase of mean crushing force F-m comparing to conventional square tube (N-CST). Parametric study shows that the collapse mode of KCBs deformed in EM is independent of aspect ratio b/t within the range of b/t <= 81.3, while for CST, the corresponding range is b/t <= 7.5. KCB inclines to collapse in EM when the dihedral angle theta or the number of modules M decrease. The F-max, F-m and CFEs of KCBs with identical M increase with the increasing theta. Whereas, the effect of M on energy absorption is relatively less important while theta remains the same. Moreover, the superiority of energy absorption for KCB subjected to dynamic loading is more significant comparing to quasi-static axial crushing.