Dynamic behaviour of graded origami honeycomb

Efforts to improve the effectiveness of cellular structures in impact scenarios has led to the introduction of gradients in their mechanical properties. A plethora of studies have shown that these gradients can be implemented to increase the energy absorption or limit the force transfer to the structure they are protecting. Whilst these findings are promising, the cost and difficulty associated with manufacturing these graded cellular structure limits their application. Origami techniques provide a convenient way to transform a 2D sheet to a 3D structure. Additionally, the underlying crease pattern can be varied to grade the topology of the structure. In this study, the ability to imbue honeycombs with a graded mechanical behaviour using origami techniques is investigated under dynamic loading. Grading is applied to the crease pattern through the variation of a simple geometric parameter. The typical honeycomb expansion manufacturing technique is preserved, as the crease pattern has one degree of freedom and is developable. 2 x 1 representative origami honeycomb cores were manufactured using a sequential stamping technique from aluminium sheets and experimentally tested using the Direct Impact Hopkinson bar and Taylor type test setup. These results validated a numerical approach that was then extrapolated to a numerical model of a 6 x 6 ungraded and graded core. Similar advantages, as those found for typical grading methods, were observed for the graded origami honeycomb when subjected to dynamic loading. These results show that origami techniques can successfully be applied to introduce a gradient in the mechanical behaviour, providing an attractive alternative to standard grading methods.