Study on mechanical properties of a hierarchical octet-truss structure

Abstract

A hierarchical octet-truss lattice material was proposed by replacing the solid strut of the octet-truss structure with a tubular re-entrant structure. The tubular re-entrant structure was constructed via a sheet rolling operation on a planar hexagonal re-entrant structure. Hierarchical octet-truss lattice materials with different relative densities were fabricated via additive manufacturing by adjusting the re-entrant structure rib thickness, and their mechanical properties were studied and compared with the finite element model predictions and shown to be in excellent agreement with each other. The effects of hierarchical ranks on the mechanical properties of structures were also discussed. Results showed that the Poisson’s ratio of the hierarchical octet-truss structure is approximately 0.3 without being affected by the introduction of structural hierarchy. The stress-strain relationships of the hierarchical octet-truss structures exhibit dual-peak characteristic. The lattice stiffness, compressive strength, and energy absorption capacity of the models increased with an increasing rib thickness of the re-entrant structure of the first-order hierarchical octet-truss structure, and the maximum value of specific energy absorption (SEA) was achieved when the relative density is 30.2%. The second-order hierarchical octet-truss structure exhibited lower collapse stress value, and a shorter stress plateau region than those of the zeroth and first-order hierarchical octet-truss structures.