PSI - Issue 68

Available online at www.sciencedirect.com Structural Integrity Procedia 00 (2025) 000–000 Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2025) 000–000 ScienceDirect

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ScienceDirect

Procedia Structural Integrity 68 (2025) 1266–1272

European Conference on Fracture 2024 Estimating microscopic defect size from Acoustic Emission Monitoring of Mode I, Mode II and Mixed-Mode I/II delamination propagation in GFRP laminates under quasi-static loads Andreas J. Brunner a *, Maria Gfrerrer b , Veronika Koss b , Gerald Pinter b a retired from Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Mechanical Systems Engineering, Überlandstrasse 129, 8600 Dübendorf, Switzerland b Montanuniversity Leoben, Materials Science and Testing of Polymers, Otto-Glöckel-Straße 2/II, 8700 Leoben, Austria Abstract In-situ acoustic emission (AE) monitoring of standard quasi-static fracture tests on fiber-reinforced polymer (FRP) composite specimens proves that delamination propagation results from the stochastic occurrence of micro- or meso-scale matrix cracks. The AE signal activity correlates with the observed speed of delamination propagation. Faster delamination propagation hence is rather due to a higher number of matrix cracks per unit time than a significantly increasing average crack size. Approaches for roughly estimating the average size and the size distributions of these matrix cracks with AE monitoring are presented and discussed. This has implications for micromechanical modelling of delamination propagation. The contribution focusses on glass fiber-reinforced epoxy, but the method is also applicable to carbon fiber reinforced thermosets and thermoplastics as well. European Conference on Fracture 2024 Estimating microscopic defect size from Acoustic Emission Monitoring of Mode I, Mode II and Mixed-Mode I/II delamination propagation in GFRP laminates under quasi-static loads Andreas J. Brunner a *, Maria Gfrerrer b , Veronika Koss b , Gerald Pinter b a retired from Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Mechanical Systems Engineering, Überlandstrasse 129, 8600 Dübendorf, Switzerland b Montanuniversity Leoben, Materials Science and Testing of Polymers, Otto-Glöckel-Straße 2/II, 8700 Leoben, Austria Abstract In-situ acoustic emission (AE) monitoring of standard quasi-static fracture tests on fiber-reinforced polymer (FRP) composite specimens proves that delamination propagation results from the stochastic occurrence of micro- or meso-scale matrix cracks. The AE signal activity correlates with the observed speed of delamination propagation. Faster delamination propagation hence is rather due to a higher number of matrix cracks per unit time than a significantly increasing average crack size. Approaches for roughly estimating the average size and the size distributions of these matrix cracks with AE monitoring are presented and discussed. This has implications for micromechanical modelling of delamination propagation. The contribution focusses on glass fiber-reinforced epoxy, but the method is also applicable to carbon fiber reinforced thermosets and thermoplastics as well. © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers Keywords: Fiber-Reinforced Polymer Composites; Delamination resistance; Micromechanical damage; Acoustic Emission;

Keywords: Fiber-Reinforced Polymer Composites; Delamination resistance; Micromechanical damage; Acoustic Emission;

* Corresponding author. Tel.: +41-58-765-4493. E-mail address: andreas.brunner@empa.ch

2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers 2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers * Corresponding author. Tel.: +41-58-765-4493. E-mail address: andreas.brunner@empa.ch

2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers 10.1016/j.prostr.2025.06.197