Analytical and numerical investigation of intra-layer failure initiation of printed materials

Abstract 3D printed materials have entered all areas of technology and have become materials for common use. The difficulty of analyzing these materials locally has been observed in the few numerical and analytical studies of their mechanical behavior, where printed PLA materials are modeled as transversely isotropic or orthotropic materials. The behavior of PLA specimens with different raster angles, produced by the fusion deposition modeling method, has been analyzed using FEM analysis and a local failure approach. The focus of this work is on intra-layer failure initiation. Eight specimens with different raster angles orientation were analyzed, each having the same printing parameters. Representative 3D models were created for each specimen, including the topographical details of the external surfaces and the raster orientation of the layers. Based on the local stress and strain state, an analysis of fracture initiation in the exterior modeled layers was carried out. The intra-layer failure of the material was expressed using a general quadratic approximation. During the FEM analysis, the submodeling technique was used to obtain the local stress and strain states accurately. Based on the results of the analytical and numerical investigations, it can be stated that the number of voids, their shape, and location, as well as the orientation of the raster angle, have a major effect on the mechanical behavior of the materials, as well as on the intra-layer failure initiation. As an experimental part, to validate the results obtained from the FEM analyses, the parts were subjected to tensile tests. During tensile loading, the material voids expand, with the possibility of a continuous channel forming on the surfaces analyzed; it can also create new material voids on the surfaces. These voids act as local stressors.