Two different modes of fracture propagation can occur when a crack encounters a weak interface in a fused filament fabricated (FFF) part: the crack either deflects into the interface, or penetrates the subsequent layers. The objective of this work is to verify the suitability of an energy- and a strength-based criterion for predicting which failure mode will occur in FFF printed parts. Four different materials, glycol-modified poly(ethylene terephthalate), polylactide acid and two different poly(methyl methacrylate) grades were examined. Fracture mechanical tests were performed on single edge-notched bending specimens for the energy-based approach and tensile tests performed on dumbbell specimens for the strength-based approach. Additionally, porosity measurements and thermal analysis were carried out to provide structural information. The energy-based approach proved unreliable for failure mode prediction. Potential problems include failure to meet the requirements of linear elastic fracture mechanics and issues with notch design. The strength-based approach, in contrast, correctly predicted the crack path for all tested materials and seems a promising candidate for failure mode prediction in FFF materials.
Bibliographische NotizFunding Information:
This research was partly carried out as part of the eFAM4Ind project (877409), which is funded by the Austrian Research Promotion Agency (FFG) and the Federal Ministry for Climate Protection, Environment, Energy, Mobility, Innovation and Technology (BMK). Moreover, the authors acknowledge support from the Montanuniversitaet Leoben. Special thanks go to Franz Grassegger for his valuable support in sample preparation.
© 2023 The Author(s)