Evaluation of Fracture Strength of Octet-Truss Lattice Structure Fabricated by 3D Printer

In this study, the fracture strength of a three-dimensional octet-truss lattice structure was investigated using finite element simuation and 3-point bending tests. The specimens were made of resin and the fracture toughness was evaluated for brittle materials without plastic deformation and ductile materials with plastic deformation. An octet truss structure was selected as the lattice structure and fracture toughness was calculated using crack opening displacement (COD) and load-displacement diagrams. As in the continuum, the fracture toughness of brittle materials was evaluated at the threshold of the stress intensity factor, KIC, and that of ductile materials at the threshold of the J integral, JIC. Furthermore, the fracture toughness value JIC for ductile materials was calculated using the maximum load values in the experiments. Although there are still issues with the technology to accurately create high-density 3-dimentional cellular structures, it was confirmed that the toughness JIC can be predicted with a certain degree of accuracy.