Crack penetration versus deflection in extrusion-based additive manufacturing – Impact of nozzle temperature and morphology

Christoph Waly, Sandra Petersmann, Florian Arbeiter

Research output: Contribution to journalArticleResearchpeer-review


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.
Original languageEnglish
Article number104032
Number of pages13
JournalTheoretical and Applied Fracture Mechanics
Issue numberOctober
Early online date5 Aug 2023
Publication statusPublished - Oct 2023

Bibliographical note

Publisher Copyright: © 2023 The Author(s)


  • Cook and Gordan
  • Crack deflection
  • Crack penetration
  • Fracture toughness
  • Fused filament fabrication
  • He and Hutchinson

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