A novel hybrid lattice design of nested cell topology with enhanced energy absorption capability

Hybridization is an effective approach to designing new lattice structures. In this paper, a novel hybrid lattice design is proposed with nested cell topology combining inner stretching-dominated struts and outer bending-dominated struts. Two hybrid lattices have been created, i.e., HS1 with inner G7 and outer octagonal cell topology, and HS2 with inner simple cubic (SC) and outer octagonal cell topology. Extensive finite element (FE) simulations were carried out to compare the compression performances of the proposed HS1 and HS2 lattices with those of the octet and octagonal lattices. The accuracy of the FE simulations was verified by energy absorption theory and comparison with experimental results in the literature. The results show that the proposed HS2 lattice possesses the best energy absorption performance. Under the same relative density conditions, the energy absorption (EA) capacity of the HS2 lattice exceeds the traditional octagonal and octet lattices by 30% and 42%, respectively. The compression stability of the hybrid lattices is also improved, which can be attributed to the simultaneous collapse pattern instead of the layer-by-layer collapse pattern and the more uniform stress distribution. In addition, the effects of geometrical deviation coefficient m of the hybrid lattices and the loading direction have also been investigated through a parametric study. It is found that the HS2 lattice achieves the maximum EA capacity at an intermediate m value of 0.5, and exhibits anisotropic responses in terms of the deformation pattern and the energy absorption efficiency under different loading directions.