The auxetic-hexagonal honeycomb is a hybrid honeycomb metastructure with in-plane Poisson's ratio controllable and multi-design parameters, and has excellent in-plane energy absorption capability compared with the conventional honeycombs. The hierarchical design method was introduced into the hybrid honeycomb metastructure to obtain a structure with better mechanical properties and energy absorption. Hierarchical hybrid honeycomb metastructures with sub-structures of triangles and arrows were proposed. The specimens were fabricated by selective laser melting using 304 stainless steel, and their elastic modulus and yield strength were systematically investigated through finite element simulation and experimental methods. The results show that the in-plane bearing and energy absorption properties of hierarchical hybrid honeycomb metastructures are greatly improved under the same areal density. The Young's modulus and strength of the metastructure with triangular sub-structure (T-AuxHex) increased by 170% and 47%, respectively, and the Young's modulus and strength of the metastructure with arrow-shaped sub-structure (A-AuxHex) increased by 39% and 9%, respectively. In addition, the specific energy absorption of the T-AuxHex is about 1.5 times that of the A-AuxHex. Therefore, the T-AuxHex has excellent in-plane bearing and energy absorption properties. Excellent energy absorption, internal space fillability and lightweight performance make hierarchical hybrid honeycomb metastructures suitable for lightweight/high-impact protection structures.

In-plane compression properties and energy absorption capability of hierarchical hybrid honeycomb metastructures

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