PSI - Issue 75

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

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Procedia Structural Integrity 75 (2025) 318–333

© 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 the responsibility of Dr Fabien Lefebvre with at least 2 reviewers per paper © 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 the scientific committee of the Fatigue Design 2025 organizers Keywords: composite structure, design, multiaxial loading, FE simulation Abstract Current specimen designs for biaxial tension-tension fatigue tests of composites are not optimal and often generate unexpected failure in fatigue tests, due to the lack of a design standard and the complexity of composite materials and multiaxial loads. And designing composite structures with uniaxial testing is not sufficient due to the multiaxiality of the stress tensor. This study aims to present an optimized specimen for multidirectional carbon fiber reinforced composites in biaxial tension-tension fatigue tests, in which thermodynamic phenomena occurring inside the specimen will be monitored by infrared thermography. A feasible specimen could be designed by numerical simulation using the finite element method. Firstly, a design criterion is proposed to ensure a failure in the gauge region, a practical manufacturing approach, and optimal conditions for temperature measurement. An initial simulation model is established to find out the proper shape, followed by a more comprehensive simulation used for determining the dimension of the specimen. Consequently, the optimized specimen is designated as a cruciform shape with a reduced gauge region. Last, two stacking sequences of specimens, referred to as cross-ply [(0/90) 6 ] s and quasi-isotropic [(0/45/90/- 45) 3 ] s , are tested in a simulation model that takes into account biaxial static and fatigue loadings, and then a thermal and fatigue simulations will be performed to validate the geometry. The favorable simulation results indicate that the optimized specimen and design approach is well-suited for multidirectional composites in biaxial fatigue tests with temperature monitoring. © 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 the scientific committee of the Fatigue Design 2025 organizers Keywords: composite structure, design, multiaxial loading, FE simulation Fatigue Design 2025 (FatDes 2025) Cruciform specimen design and manufacture for multidirectional carbon fiber reinforced composites subjected to biaxial tension tension fatigue test Aijia Li a,b , Christian Garnier a,* , Marie-Laetitia Pastor b , Xiaojing Gong b , Clément Keller a a University of Technology Tarbes Occitanie Pyrénées, Laboratoire Génie de Production (LGP), 47 avenue d'Azereix,Tarbes 65000, France b University of Technology Tarbes Occitanie Pyrénées, Institut Clément Ader (ICA), 47 avenue d'Azereix,Tarbes 65000, France Abstract Current specimen designs for biaxial tension-tension fatigue tests of composites are not optimal and often generate unexpected failure in fatigue tests, due to the lack of a design standard and the complexity of composite materials and multiaxial loads. And designing composite structures with uniaxial testing is not sufficient due to the multiaxiality of the stress tensor. This study aims to present an optimized specimen for multidirectional carbon fiber reinforced composites in biaxial tension-tension fatigue tests, in which thermodynamic phenomena occurring inside the specimen will be monitored by infrared thermography. A feasible specimen could be designed by numerical simulation using the finite element method. Firstly, a design criterion is proposed to ensure a failure in the gauge region, a practical manufacturing approach, and optimal conditions for temperature measurement. An initial simulation model is established to find out the proper shape, followed by a more comprehensive simulation used for determining the dimension of the specimen. Consequently, the optimized specimen is designated as a cruciform shape with a reduced gauge region. Last, two stacking sequences of specimens, referred to as cross-ply [(0/90) 6 ] s and quasi-isotropic [(0/45/90/- 45) 3 ] s , are tested in a simulation model that takes into account biaxial static and fatigue loadings, and then a thermal and fatigue simulations will be performed to validate the geometry. The favorable simulation results indicate that the optimized specimen and design approach is well-suited for multidirectional composites in biaxial fatigue tests with temperature monitoring. Fatigue Design 2025 (FatDes 2025) Cruciform specimen design and manufacture for multidirectional carbon fiber reinforced composites subjected to biaxial tension tension fatigue test Aijia Li a,b , Christian Garnier a,* , Marie-Laetitia Pastor b , Xiaojing Gong b , Clément Keller a a University of Technology Tarbes Occitanie Pyrénées, Laboratoire Génie de Production (LGP), 47 avenue d'Azereix,Tarbes 65000, France b University of Technology Tarbes Occitanie Pyrénées, Institut Clément Ader (ICA), 47 avenue d'Azereix,Tarbes 65000, France

* Corresponding author. Tel.: +330567450105 E-mail address: christian.garnier@uttop.fr; * Corresponding author. Tel.: +330567450105 E-mail address: christian.garnier@uttop.fr;

* *

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) 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)

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 the responsibility of Dr Fabien Lefebvre with at least 2 reviewers per paper 10.1016/j.prostr.2025.11.033