In-Plane Multi-Directional Dynamic Crushing of Hexagonal Honeycomb

Hexagonal honeycomb is widely used in structural passive safety protection because of its low density, high specific strength and stable deformation process. The effects of cell wall thickness, initial impact velocity and impact direction on the deformation modes and crush characteristic of the hexagonal honeycomb are investigated with an impact finite element model (FEM), in which the cell wall thickness and out-of-plane thickness of the hexagonal honeycomb are variable. The results showed that, when the hexagonal honeycomb was impacted in the transverse plane and longitudinal plane, the impact end of the structure always shrank inward until the middle of the hexagonal honeycomb was compacted, and finally the whole structure was compressed. When it was impacted in the 60 ∘ oblique plane, there was no inward shrinkage, and the whole structure was compressed and deformed from the impact end toward the fixed end. Under the same initial impact velocity in different impact directions, the initial peak force (IPF) and specific energy absorption (SEA) of the hexagonal honeycomb increased with the cell wall thickness. When the cell wall thickness was constant, the IPF and SEA of the hexagonal honeycomb increased with the initial impact velocity. Then empirical formulas for IPF and SEA of the hexagonal honeycomb crushing were obtained and verified by simulation. It was found that the errors of proposed empirical formulas for IPF and SEA of the hexagonal honeycomb both were within 10%, which means the empirical formulas can be used to predict the crashworthiness of the hexagonal honeycomb.