A simplified fracture prediction approach for FDM-fabricated notched PLA components with cross-ply raster pattern: experimental verification by the semi-circular bend specimen data

Mode I translaminar fracture of the semi-circular bend (SCB) specimens containing U- and rounded V-notches (RV-notches) additively manufactured from Polylactic acid (PLA) is investigated. It is aimed to examine whether incorporating the limited tensile nonlinearity of the printed PLA through the equivalent material concept (EMC) can improve the fracture load prediction obtained within the virtual isotropic material concept (VIMC) framework. For this purpose, two modeling approaches, namely VIMC and VIMC-EMC, are applied in conjunction with the mean stress (MS) criterion, maximum tangential stress (MTS) criterion, averaged strain energy density (ASED) criterion, and cohesive zone model (CZM) applied via the extended finite element method (XFEM). The results show that the direct VIMC approach combined with MS criterion yields the best predictions with MAPE values less than 5%. The EMC correction has only a limited influence on MS and MTS criteria, while its effect on ASED criterion is also marginal. In contrast, VIMC-EMC approach improves the CZM-XFEM predictions, reducing MAPE value between 6 and 9%. Therefore, the EMC correction should not be regarded as universally beneficial for FDM-fabricated PLA, but should be evaluated according to the fracture criterion and material response. Scanning electron microscopy (SEM) observations confirm a predominantly brittle fracture behavior for both notch geometries, although the U-notched specimens exhibit rougher fracture surfaces which are well consistent with their higher fracture loads experimentally acquired. Overall, VIMC-MS approach is shown to provide a simple, accurate, and computationally efficient route for predicting Mode I fracture loads of notched printed PLA components with a cross-ply [0/90] s raster pattern without requiring modeling the printed material layer-by-layer.