Effect of stacking direction and raster angle on the fracture properties of Onyx 3D printed components: A mesoscale analysis

Abstract

3D printing is a technology that has gained increasing importance both in academia and industry for the possibilities offered. Among the many, one of the most appealing is the possibility to choose different printing configurations, tailoring stacking direction, and raster angle. The choice of such parameters deeply influences the structural response, as already shown in the literature. This study aims at providing a deep understanding of the phenomena taking place at the mesoscale level which justify such differences in the fracture behavior. An experimental campaign is carried out with a Single Edge Notch Bending (SENB) specimen printed in Onyx using four different combinations of raster angles and stacking directions. The results are compared in terms of mechanical response, fracture toughness and surface roughness to identify the main driving mechanisms during the fracture process. The same bending test is replicated numerically, aiming at comparing the fracture toughness values obtained experimentally with the ones used in the simulation to match the experimental curves. The study shows that the stacking direction and the raster angle deeply influence the fracture behavior and the mechanical properties of the specimen, along with the fracture toughness and surface roughness. In particular, it is highlighted how improved mechanical behavior can be achieved by printing the specimen in the vertical direction and with a raster angle of 45°/−45°. Moreover, useful fracture toughness values are identified for different combinations of printing parameters by means of a Cohesive Zone Model formulation, providing useful input values for numerical simulations.