Experimental and numerical investigation of crack propagation in additively manufactured model using extended finite element method (XFEM)

This study investigates the fracture mechanics of stereolithography (SLA) resin by integrating an experimental study based on ASTM D5045 standards that validates using the extended finite element method (XFEM) numerical simulations. While SLA offers high precision, geometric discontinuities such as voxel-stepping effects often render bulk material properties insufficient for predicting failure in notched components. Experimental compact tension (CT) testing on six as-printed specimens yielded a mean conditional fracture toughness (KQ) of 0.79±0.04 MPa·m1/2 with a low coefficient of variation (CV) of 5.15%, demonstrating high process repeatability. The numerical XFEM model showed strong agreement with experimental data, predicting a fracture toughness (KXFEM) of 0.82 MPa·m1/2, which corresponds to a deviation of only 3.8%. Key findings reveal that the effective local strength at the notch tip drops drastically to 17 MPa compared to the bulk tensile strength of 46 MPa. This identifies a critical strength reduction factor (SRF) of approximately 2.7 caused by stress concentrations at printed micro-defects. Furthermore, SEM and FTIR analyses confirmed that failure is governed by a brittle fracture mechanism driven by a dense cross-linked network and crack initiation at voxel steps.