PSI - Issue 68

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

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Procedia Structural Integrity 68 (2025) 3–8

European Conference on Fracture 2024 Fracture properties of interlocking structure by sickle joints printed with a stereolithography 3D printer European Conference on Fracture 2024 Fracture properties of interlocking structure by sickle joints printed with a stereolithography 3D printer

Masayuki Arai a, *, Yukiho Saito b , Hayato Fujita c , Yuxian Meng a a Department of Mechanical Engineering, Tokyo University of Science, Tokyo 125-8585, Japan b Honda Motor Co., Ltd., Tokyo 107-8556, Japan c Graduate School of Mechanical Engineering, Tokyo University of Science, Tokyo 125-8585, Japan Masayuki Arai a, *, Yukiho Saito b , Hayato Fujita c , Yuxian Meng a a Department of Mechanical Engineering, Tokyo University of Science, Tokyo 125-8585, Japan b Honda Motor Co., Ltd., Tokyo 107-8556, Japan c Graduate School of Mechanical Engineering, Tokyo University of Science, Tokyo 125-8585, Japan

Abstract The crack deflection mechanism is very effective in improving the fracture toughness of brittle materials, such as ceramics. In this study, we attempted to improve the fracture toughness using a sickle-joint structure, which is a classical Japanese joining technique. It is an interlocking structure in which the female and male parts are secured in convex and recessed shapes. Finite element analysis was performed on a sickle-joint-containing Compact Tension (CT) specimen to verify the effectiveness of the high toughness achieved by the interlocking structure. The results show that the fracture energy improves approximately fourfold. A similar effect was confirmed by the tensile test results of a CT specimen 3D-printed by stereolithography. © 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: crack path deflection; sickle joint, finite element analysis; fracture energy; stereolithography 3D printer 1. Introduction Crack propagation path deflection is a method used to improve the fracture toughness of brittle materials such as ceramics (Rubinstein, 1990), by deflecting the crack propagation path away from the linear crack. Ceramic matrix composites (CMCs) benefit from this mechanism ( Ahn et al., 1998 ) . However, this method has technical problems, such as the variability in the material’s strength properties and its high manufacturing cost. Another improvement method is the introduction of biomimetics, which is inspired by the excellent functions of organisms in nature. The Abstract The crack deflection mechanism is very effective in improving the fracture toughness of brittle materials, such as ceramics. In this study, we attempted to improve the fracture toughness using a sickle-joint structure, which is a classical Japanese joining technique. It is an interlocking structure in which the female and male parts are secured in convex and recessed shapes. Finite element analysis was performed on a sickle-joint-containing Compact Tension (CT) specimen to verify the effectiveness of the high toughness achieved by the interlocking structure. The results show that the fracture energy improves approximately fourfold. A similar effect was confirmed by the tensile test results of a CT specimen 3D-printed by stereolithography. © 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: crack path deflection; sickle joint, finite element analysis; fracture energy; stereolithography 3D printer 1. Introduction Crack propagation path deflection is a method used to improve the fracture toughness of brittle materials such as ceramics (Rubinstein, 1990), by deflecting the crack propagation path away from the linear crack. Ceramic matrix composites (CMCs) benefit from this mechanism ( Ahn et al., 1998 ) . However, this method has technical problems, such as the variability in the material’s strength properties and its high manufacturing cost. Another improvement method is the introduction of biomimetics, which is inspired by the excellent functions of organisms in nature. The © 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.: +81-3-5876-1823; fax: +81-3-5876-1823. E-mail address: marai@rs.tus.ac.jp * Corresponding author. Tel.: +81-3-5876-1823; fax: +81-3-5876-1823. E-mail address: marai@rs.tus.ac.jp

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

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.2025.06.015