Investigating the Role of Infill Geometry and Density on the Mode-I Fracture Toughness of Polymeric Materials Fabricated by Fused Filament Fabrication

Abstract

Abstract The Fused Filament Fabrication (FFF) method is a 3D printing technology that allows for the creation of thermoplastic materials with various infill geometries in cellular and lattice forms, which facilities designing high-performance lightweight materials. This study aims to investigate the effect of infill geometry and density on the mode-I fracture toughness of thermoplastic materials fabricated by the FFF method. Polylactic acid (PLA) is chosen as the model material. Compact tension fracture tests are performed to measure the mode-I fracture toughness. The digital image correlation technique is used to measure the crack tip strain field varying with the examined parameters. The results of the study suggest that the elastic fracture toughness scales with the infill density in a power-law relationship. For the examined range of relative density, the correlation factor exhibits minor dependence on the infill geometry, with a value of 3. However, when considering inelastic fracture energy dissipation, the triangle infill geometry was found to have the highest crack resistance due to toughening arising from crack tip wandering. These findings have broad applications, and the proposed scaling laws can help predict the fracture toughness of polymeric materials made through the FFF method.