Evaluation of the fracture strength of three-dimensional lattice structures containing a crack

Abstract

Owing to the rapid development of additive manufacturing technology, more precise and complex 3D lattice structures can be manufactured easily. In this study, the brittle fracture toughness of 3D lattice structures was investigated by finite element analysis and experimental bending tests. The existence of singular stress fields in 3D lattice structures is highly dependent on the crack length and the relative density of the lattice cores. In this study, two types of lattice core containing cracks (termed BCC and FBCCZ) were selected as analytical models, and the singular stress field was investigated by observing the change in stress values during fracture. Also, based on our numerical calculation, empirical expressions for the brittle fracture toughness KIC of both lattice structures were obtained and compared with experimental results. The experimental values of fracture toughness KIC can be predicted within an error margin of approximately 20% by considering the effective length of the strand and the amount of plastic strain that occurs before fracture.

Keywords

• lattice structure
• brittle fracture strength
• stress intensity factor
• finite element analysis
• 3-point bending test