PSI - Issue 68

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Procedia Structural Integrity 68 (2025) 1273–1279 Structural Integrity Procedia 00 (2024) 000–000 Structural Integrity Procedia 00 (2024) 000–000

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European Conference on Fracture 2024 Obtaining traction-separation laws of adhesive joints using optical fiber strain measurements - Part B (Mode III) Lukas Dominik Geisel a , Stephan Marzi a a Institute of Mechanics and Materials, Technische Hochschule Mittelhessen, Wiesenstrasse 14, 35390 Gießen, Germany Abstract This work applies a new measurement method of cohesive laws presented in the homonymous companion paper by Aydin and Marzi (2024). The new method allows the measurement of multiple cohesive laws from a single specimen using only backface strain measurements, obtained with optical fibers. Previously obtained and published results of four-point bend out-of-plane loaded single-leg bending (4-OSLB) specimens bonded with a structural adhesive were re-evaluated, to obtain mode III traction-separation laws. Part A is focused on the measurement of mode I traction-separation laws of similar adhesive using DCB specimens. © 2025 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of ECF24 organizers. Keywords: Mode III; Adhesive joints; Traction-separation laws; Optical fiber measurement European Conference on Fracture 2024 Obtaining traction-separation laws of adhesive joints using optical fiber strain measurements - Part B (Mode III) Lukas Dominik Geisel a , Stephan Marzi a a Institute of Mechanics and Materials, Technische Hochschule Mittelhessen, Wiesenstrasse 14, 35390 Gießen, Germany Abstract This work applies a new measurement method of cohesive laws presented in the homonymous companion paper by Aydin and Marzi (2024). The new method allows the measurement of multiple cohesive laws from a single specimen using only backface strain measurements, obtained with optical fibers. Previously obtained and published results of four-point bend out-of-plane loaded single-leg bending (4-OSLB) specimens bonded with a structural adhesive were re-evaluated, to obtain mode III traction-separation laws. Part A is focused on the measurement of mode I traction-separation laws of similar adhesive using DCB specimens. © 2025 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of ECF24 organizers. Keywords: Mode III; Adhesive joints; Traction-separation laws; Optical fiber measurement © 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 Cohesive laws are obtained by measuring the energy release rate (ERR) and the crack tip opening displacement (CTOD). The former is usually evaluated using methods based upon the Irwin-Kies equation (requires a compliance calibration and force measurements) or the J -integral (requires force and rotation measurements). The CTOD is typi cally measured using extensometers or digital image correlation (DIC) systems. However, both of these methods are in some cases complicated to implement with the desired test setup. CTOD measurements via DIC are often di ffi cult to obtain with most of the commonly used mode II and mode III test setups. One such case is the 4-OSLB test setup, which was initially proposed by Yoshihara (2006) and modified for the testing of structural adhesives by Geisel and Marzi (2024). Here, no practical line of sight to the crack tip exists. This necessitates the usage of extensometers, which need special fixtures that can also introduce some problems. An alternative measurement and evaluation method, which only needs strain measurements along the fracture pro cess zone for both the ERR and the COD, is presented in the homonymous companion paper by Aydin and Marzi Cohesive laws are obtained by measuring the energy release rate (ERR) and the crack tip opening displacement (CTOD). The former is usually evaluated using methods based upon the Irwin-Kies equation (requires a compliance calibration and force measurements) or the J -integral (requires force and rotation measurements). The CTOD is typi cally measured using extensometers or digital image correlation (DIC) systems. However, both of these methods are in some cases complicated to implement with the desired test setup. CTOD measurements via DIC are often di ffi cult to obtain with most of the commonly used mode II and mode III test setups. One such case is the 4-OSLB test setup, which was initially proposed by Yoshihara (2006) and modified for the testing of structural adhesives by Geisel and Marzi (2024). Here, no practical line of sight to the crack tip exists. This necessitates the usage of extensometers, which need special fixtures that can also introduce some problems. An alternative measurement and evaluation method, which only needs strain measurements along the fracture pro cess zone for both the ERR and the COD, is presented in the homonymous companion paper by Aydin and Marzi 1. Introduction 1. Introduction

∗ Corresponding author. Tel.: + 49-641-309-2124 E-mail address: stephan.marzi@me.thm.de ∗ Corresponding author. Tel.: + 49-641-309-2124 E-mail address: stephan.marzi@me.thm.de

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.2025.06.198 2210-7843 © 2025 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of ECF24 organizers. 2210-7843 © 2025 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of ECF24 organizers.