Mechanical Performance and Structural Integrity of 3D-Printed Polylactic Acid in Tensile Testing: Influence of Hole Fabrication Technique and Process Parameters

Abstract

Background: The mechanical performance of 3D-printed components is known to depend on process parameters, but the influence of hole-generation techniques on failure behavior remains insufficiently explored. Objective: This study investigates how raster orientation, infill density, and hole fabrication method affect the tensile strength and stress concentration in PLA specimens produced by fused deposition modeling (FDM). Methods: standardized tensile specimens were manufactured with three raster angles (0°, 45°, 90°), four infill densities (25%–100%), and two hole-generation approaches—post-drilled holes and integrated printed holes. Mechanical tests were conducted according to ASTM D638 and ASTM D5766, and stress concentration factors (K_t) were calculated. Failure surfaces were examined using optical microscopy. Results Specimens with 0° raster angle and 100% infill showed the highest strength. Post-drilled samples consistently outperformed printed-hole counterparts in terms of tensile strength and K_t values. Microscopy revealed that printed holes introduced interlayer misalignment and shell–infill discontinuities, facilitating early crack initiation. Conclusions: The findings highlight that hole geometry alone is not sufficient to ensure structural integrity. The drilled-hole specimens consistently outperformed printed-hole samples in terms of tensile strength and failure resistance. The method of hole fabrication plays a critical role in failure performance and should be considered a key design parameter in FDM applications involving stress concentrators.