An origami-inspired structure with graded stiffness

Origami-inspired structures and mechanical metamaterials are often made up of individual tessellating repeat units, the folding and relative geometry of which determine the overall mechanical properties. If these units are identical, then the mechanical behaviour of the structure is uniform throughout, meaning that it is not able to adapt to changeable loading conditions. Here we create and study an origami structure, based on the Miura-ori folding pattern, which has a varying geometry over its volume and graded stiffness. Using kinematic analysis, we show how geometric parameters of the folding pattern can be varied to create both rigid foldable and self locking stages. We demonstrate both experimentally and numerically that the structure can achieve periodically graded stiffness when subjected to quasi-static out-of-plane compression, and the mechanical responses can be tuned by changing the underlying geometric design. We obtain a structure with superior energy absorption capability to uniform tessellating repeat units, and anticipate that this strategy could be extended to other structures and metamaterials to impart them with non-uniform and graded mechanical properties. (C) 2017 Elsevier Ltd. All rights reserved.