Dynamic mechanical behavior of hierarchical mechanical metamaterials

The natural material featuring hierarchical structure are always of remarkable mechanism properties. Generally, most researches are focused on the quasi-static mechanical properties while limited researches analyze the dynamic mechanical behavior of hierarchical materials. In this paper, hierarchical mechanical metamaterials were fabricated, and dynamic mechanical properties were studied experimentally and simulationally. Applying 3D laser lithography, we produced hierarchical metamaterials of different orders. After plating with electrodeposited Ni coatings and removing the polymer cores inside, we finally obtained finished samples including three material systems. Compression experiments under different strain rates were performed for dynamic mechanical characterization. The results revealed that the number of orders and material systems of hierarchical metamaterials significantly effected their dynamic mechanical behavior and energy absorption. To further explain the underlying deformation mechanisms, simulation models were established and validated by comparing with experiments. This study will shed light on designing hierarchical materials of different length scales for crushing protection.