Impact behaviour of hexagonal hierarchical honeycombs

Honeycomb materials have been widely used in architecture, aerospace, and civil engineering in recent years. In this work, hexagonal hierarchical honeycombs with regular triangular substructures are studied. Based on the analytical model, expressions of the relative density and collapse stress are derived. Numerical results show that the substructure number, aspect ratio, and wall angle have different influences on the relative density. The collapse stress of hexagonal hierarchical honeycombs is sensitive to the relative density. Deformation modes of honeycomb structures depend on impact velocities, and secondary deformation is observed due to the introduction of triangular substructures. The kinetic energy and absorption energy of hexagonal hierarchical honeycombs are also provided to investigate the energy transformation and absorption. Because of the secondary deformation, hierarchical honeycombs have better energy absorption performance than conventional ones.