Investigation on the fracture behavior of octet-truss lattice based on the experiments and numerical simulations

Abstract

Octet-truss lattice is an excellent carrier for structure–function integration because of its natural porous characteristics and remarkable bearing capacity. Currently, a significant discussion in its engineering applications revolves around assessing the fracture toughness of the lattice structure. In this paper, the single edge notched bend (SENB) specimens composed of PolyMaxTMPLA with shallow crack are prepared using the Fused Deposition Modelling (FDM) method, and three-point bending tests are conducted to investigate the fracture behavior of the octet-truss lattices. Based on the elastic–plastic fracture behavior of the specimens, the J-integral method is used to calculated the effective fracture toughness and the effect of shallow crack on the fracture toughness was considered. The experimental results show that the effective fracture toughness of the polymer specimens increases linearly with the relative density and the square root of truss length. To study the fracture behavior of lattice structure deeply, the numerical simulations are performed to further analyze the fracture behavior of the structures and verified by the experimental results. The results suggest that the fracture at the nodes and the truss near the nodes is the main failure mode of the specimens. Specially, the truss in the X-Z plane always breaks before the X-Y plane, while the deformation of truss in the Y-Z plane is always elastic. A prediction formula of the effective fracture toughness of 3D printed PLA polymer octet-truss lattice is determined based on a non-dimensional parameter sensitive to the loading mode.