TY - JOUR

T1 - Crack penetration versus deflection in extrusion-based additive manufacturing – Impact of nozzle temperature and morphology

AU - Waly, Christoph

AU - Petersmann, Sandra

AU - Arbeiter, Florian

N1 - Publisher Copyright: © 2023 The Author(s)

PY - 2023/10

Y1 - 2023/10

N2 - 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.

AB - 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.

KW - Cook and Gordan

KW - Crack deflection

KW - Crack penetration

KW - Fracture toughness

KW - Fused filament fabrication

KW - He and Hutchinson

UR - http://www.scopus.com/inward/record.url?scp=85167427546&partnerID=8YFLogxK

U2 - 10.1016/j.tafmec.2023.104032

DO - 10.1016/j.tafmec.2023.104032

M3 - Article

AN - SCOPUS:85167427546

VL - 127.2023

JO - Theoretical and Applied Fracture Mechanics

JF - Theoretical and Applied Fracture Mechanics

SN - 0167-8442

IS - October

M1 - 104032

ER -