Bio-inspired hierarchical honeycomb metastructures with superior mechanical properties

Inspired by the hierarchical macro and microstructures widely found in nature, this study proposes a novel hierarchical honeycomb design methodology. The aim is to overcome the shortcoming of conventional honeycomb structures that have poor energy absorption properties due to damage after loading. Thereby, a new honeycomb structure with several superior mechanical properties is obtained. Firstly, triangular, square, and circular holes are used at the third microstructure level. Moreover, their filling types, filling principles, and dimensional design basis are thoroughly investigated. And a hierarchical honeycomb is generated by arranging them on the cell walls of a conventional honeycomb according to the conformal design guidelines. Finally, the performance of the designed hierarchical honeycomb metastructure is analyzed and compared by simulation and experiment. It is found that the hierarchical honeycomb metastructures exhibit significantly improved overall mechanical properties compared with the conventional honeycomb structures. The hierarchical honeycomb metastructures with different holes have different performance enhancement effects on the conventional honeycomb structure. Among them, the hierarchical honeycomb metastructures with circular holes have the best performance improvement compared to conventional honeycomb structures. The hierarchical square honeycomb with circular holes has 0.84% stiffness loss, 19.38% strength loss, and 199.67% energy absorption performance improvement. However, the hierarchical hexagon honeycomb with circular holes has 1.06% stiffness improvement, 5.55% strength loss, and 345.24% energy absorption performance improvement. Additionally, the reliability of the novel honeycomb metastructure is verified to be better than the conventional honeycomb structure with the spacecraft return capsule shell.