The influence of in-plane raster angle on tensile and fracture strengths of 3D-printed PLA specimens

Abstract

The present paper studies the effect of in-plane raster orientation on the tensile and fracture strengths of poly-lactic acid (PLA) samples made by fused deposition modeling technique. Four different raster angles of 0/90°, 15/−75°, 30/−60°, and 45/−45° are selected for the dog-bone and the semi-circular bending (SCB) specimens to investigate the tensile and mode I fracture behavior of the 3D-printed PLAs. The results demonstrate anisotropic behavior in the both tensile and fracture properties of the material. Additionally, due to the plastic deformations of the material prior to the fracture initiation load, the J-integral is selected as the fracture characterizing parameter. To do so, some elastic-plastic finite element simulations were performed to obtain the critical values of J-integral. The raster orientation of 45/−45° exhibits the best performance with maximum percent elongation and fracture resistance compared with the three other raster angles. While the critical J-integral of 45/−45° sample is 6815 J/m2, this value is 1839 J/m2 for 0/90° sample. In addition, in the samples used for fracture tests, the crack growth path is investigated to analyze the effect of raster orientation on the fracture trajectories of the SCB specimens. Based on the observed crack growth trajectories, the difference between the fracture loads and the amounts of plastic deformation in the SCB samples with different raster orientations are justified. Finally, the scanning electron microscopy (SEM) is utilized to explore the failure mechanism in the dog-bone samples.