Experimental and Numerical Investigation of the Effect of Aperture Angle on the Apparent Tensile Response of FDM 3D-Printed PLA Specimens

This study presents a combined experimental–numerical investigation of the tensile behavior of fused deposition modeling (FDM) printed polylactic acid (PLA) dog-bone specimens containing paired through-thickness circular apertures at controlled orientations. Twenty-seven specimens were fabricated in nine groups: one solid reference and eight perforated configurations with hole radius R = 1 mm, spacing d = 5 mm, and angles ranging from 0° to 105°. Quasi-static tensile tests were conducted to obtain engineering stress–strain curves. Two stress measures were defined: gross-section nominal stress (σ_nom,max) based on the original cross-section, and net-section stress (σ_net,max) based on the minimum load-bearing area. Results show that σnom,max is strongly dependent on aperture angle, decreasing to 22.25 ± 0.82 MPa at 15° and increasing to 27.98 ± 1.01 MPa at 105°, compared to 27.23 ± 1.50 MPa for solid specimens. A critical angle (θ_c ≈ 23.58°) distinguishes regimes where the minimum section intersects one or both holes. In the one-hole regime, σ_net,max increases monotonically from 45° onward, isolating stress concentration effects. The apparent Young’s modulus (E_app) remains nearly constant (1444.02 ± 37.53 MPa), indicating minimal influence on elastic behavior. Finite element simulations accurately replicate experimental trends, confirming the role of aperture orientation in stress distribution and failure response.