Effect of nozzle diameter and raster orientation on tensile and fracture behavior of FDM-PLA specimens under mixed-mode I/II loading

Fused deposition modeling (FDM) is a material extrusion technique that works by extruding molten filament on a heated platform. In this method, several manufacturing parameters are engaged which affect the mechanical performance of printed parts. In this study, the effects of nozzle diameter on tensile (under two loading rates) and mixed-mode I/II fracture behavior of printed specimens were examined. The obtained results revealed that testing speed had a minor effect on basic mechanical properties. For instance, ultimate tensile strengths of tensile specimens printed with 1 mm nozzle diameter were 32.56 and 39.71 MPa for test speeds of 1 and 5 mm/min, respectively. Higher nozzle diameters resulted in higher mechanical properties and fracture resistance (e.g., specimens printed with 45/-45 degrees raster angle with 0.4 and 1 mm nozzle diameters indicated fracture loads of 4520 and 5071 N, respectively). Besides, fracture loads were predicted through the equivalent material concept coupled with J-integral method. Nozzle diameter effect on tensile and fracture behavior of FDM-PLA specimens is studied. FDM-PLA tensile specimens are tested with two loading rates of 1 and 5 mm/min. Fracture loads of the tested specimens are predicted through the EMC-J criterion. Failure mechanisms are studied through the SEM pictures of the fracture surfaces.