Assessment of mixed-mode I/II fracture behavior of blunt V-notched 3D-printed PLA specimens: A strategy of material simplification using VIMC and EMC

Abstract

Fracture behavior of square plates made from Polylactic Acid (PLA) using Fused Deposition Modeling (FDM), containing rounded V (RV) notches, is analyzed under diagonal tensile loading. This study examines the influence of notch geometry, specifically the opening angle, orientation, and tip radius on the structural load-bearing capacity. Fracture load predictions are performed using the Mean Stress (MS) and Maximum Tangential Stress (MTS) criteria by taking advantages of a strategy of material simplification that employs the Virtual Isotropic Material Concept (VIMC) and the Equivalent Material Concept (EMC). The results indicate that notch geometry significantly affects fracture strength. Plates with larger opening angles show reduced stress concentration and improved fracture resistance, while narrower angles lead to higher localized stresses. Similarly, increasing the notch tip radius enhances fracture resistance by promoting more favorable stress distribution. Compared to conventional brittle polymers such as cast Polymethyl-methacrylate (PMMA), 3D-printed PLA demonstrates reduced sensitivity to notch-induced stress concentration, attributed to its relatively large characteristic length. Scanning Electron Microscopy (SEM) analysis reveals a transition from ductile to brittle failure mechanisms as the notch angle increases. These findings highlight the importance of optimizing notch geometry and raster orientation to improve the mechanical performance of FDM-fabricated PLA parts. The combined application of VIMC and EMC with MS and MTS criteria provides a reliable and practical framework for predicting fracture in 3D-printed structures, without the need for complex anisotropic modeling.