Mechanical properties and deformation mechanism of laser melting octagonal double pyramid and Kelvin hybrid lattice structure

Due to their excellent mechanical properties, dot matrix structures show a broad application prospect for spacecraft lightweight structures and cushioning energy absorbing devices. In this paper, two hybrid structures based on octagonal bipyramidal structure and Kelvin structure are proposed, and the corresponding dot matrix structures are prepared by selected laser melting. The mechanical properties, energy-absorption characteristics and deformation mechanisms of the hybrid structures are systematically investigated through experiments and simulation. It shows that the mechanical and energy-absorbing properties of the hybrid structures are significantly enhanced; when the relative density is the same, the energy-absorbing efficiency of the hybrid structure 1 is increased by 15.7%, and the specific strength and specific energy-absorption of the hybrid structure 2 are increased by 93% and 92%, respectively. In terms of the deformation mechanism, the hybrid structure 1 uniformly collapses, which shows a bending-dominant deformation mechanism; while the hybrid structure 2 collapses layer by layer throughout the whole process from bottom to top. In order to further improve the deformation mechanism and enhance the mechanical properties of the hybrid structure, the geometric parameters of the hybrid structures are investigated. It is found that adjusting the ratio of inner and outer rod diameters can realize optimization of the hybrid structure. When λ = 0.75, comprehensive performance of hybrid structure 1 is best, with in its specific strength and specific energy absorption increasing by 21% and 10% respectively.