Experimental and Theoretical Evaluation of Notch Strength in MEX-Printed Acrylonitrile Butadiene Styrene Under Symmetrical Three-Point Bending

Material extrusion (MEX) is an extensively used additive manufacturing technique that facilitates the fabrication of precise physical components with complex geometries through successive material deposition. However, the anisotropic behavior inherent to MEX-printed materials can substantially influence their fracture response. This study examines the fracture behavior of U- and blunt V-notched (BV-notched) MEX-printed Acrylonitrile Butadiene Styrene (ABS) under symmetrical three-point bending using rectangular specimens with a symmetrical [0/90]s cross-ply printing architecture. To this end, three different notch root radii within the 1–4 mm range are experimentally investigated, and the measured fracture loads are compared with theoretical-numerical predictions obtained by integrating the virtual isotropic material concept (VIMC) with four failure models, namely the point stress (PS), mean stress (MS), and averaged strain energy density (ASED) criteria, as well as the extended finite element method coupled with a cohesive zone model (XFEM-CZM). All four VIMC-based criteria provide reasonable correspondence with the experimental results. Among them, the ASED-VIMC criterion exhibits the lowest average percentage difference of 5.7% for the 1–4 mm range of notch root radius, symmetrical [0/90]s cross-ply printing architecture, and symmetrical three-point bending, followed by the PS-VIMC criterion with 7.4%. ASED-VIMC criterion also demonstrates the most consistent performance for both notch configurations, likely due to its lower sensitivity to notch geometry.