Dynamic uniaxial crushing behaviour of three orthogonally graded stacked miura-ori metastructures

In this study, the dynamic crushing behaviour of graded stacked Miura-ori metastructure is investigated. Firstly, three types of nested-in stacked Miura-ori metastructures, each with a geometric gradient design along one of the three orthogonal directions ( z , y , and x ), are proposed. Three uniformly stacked Miura-ori specimens are fabricated and tested under quasi-static crushing conditions along three directions. The numerical model is then verified using the testing results. The calibrated model is utilized to predict the uniaxial crushing behaviour and structural response of metastructures under dynamic compression in their respective gradient directions. The length-graded metastructure shows better energy absorption and lower initial peak compared to its uniform counterpart under crushing in z direction. Comparable impact performance and stable deformation mode are observed for both the height-graded and width-graded metastructures under crushing in y and x directions, respectively. As the loading rate increases from 10 to 100 m/s along z direction, the layer-by-layer sequential collapse from proximal end is the dominant deformation mode for the uniform and positively length-graded metastructures. In contrast, the initial collapse of the negatively length-graded metastructure occurs at two ends and then propagates to the middle. The effects of impact speed and graded interval size on structural response of length-graded metastructure under crushing in z direction are also explored.