PSI - Issue 72

Available online at www.sciencedirect.com

ScienceDirect

Procedia Structural Integrity 72 (2025) 61–68

12th Annual Conference of Society for Structural Integrity and Life (DIVK12) Single-leg bending (SLB) analysis of a structural adhesive as a function of the adhesive thickness A.F.L. Macedo a , R.D.S.G. Campilho a,b, *, A.L. Faria a , M. Belhouari c , K. Madani c a Department of Mechanical Engineering, ISEP – School of Engineering, Polytechnic Institute of Porto, R. Dr. António Bernardino de Almeida, 431, 4200-072 Porto, Portugal. b Institute of Science and Innovation in Mechanical and Industrial Engineering, Rua Dr. Roberto Frias, 400, 4200-465 Porto, Portugal. c Department of Mechanical Engineering, University of Sidi Bel Abbes, BP 89, Cité Ben M’hidi, 22000, Sidi Bel Abbes, Algeria. Abstract The mixed-mode static fracture analysis of bonded joints using cohesive zone models (CZM) requires accurate predictions of adhesive strength and fracture toughness. Tensile and shear fracture toughness ( G IC and G IIC ), along with their mixed-mode behaviors, significantly vary with the adhesive thickness ( t A ). This work focuses on the numerical analysis of how t A influences the mixed-mode fracture process in adhesive joints. Experimental data from single-leg bending (SLB) tests is used, involving composite adherends and a ductile adhesive, with t A ranging from 0.1 to 2.0 mm. The study includes a comparison between experimental and numerical load-displacement ( P -  ) curves for validation purposes, followed by the estimation of CZM laws and validation of the fracture envelope across all t A . The findings enabled a comprehensive numerical evaluation of the t A effect on fracture behavior in adhesive joints, leading to the proposal of a numerical methodology to analyze mixed-mode bonded joints. © 2026 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 Aleksandar Sedmak, Branislav Djordjevic, Simon Sedmak Dr. Simon Sedmak, ssedmak@mas.bg.ac.rs, Innovation Center of Faculty of Mechanical Engineering, Belgrade, Serbia

Keywords: Adhesive bond; Structural adhesive; Fracture test; Finite element method; CZM approach

1. Introduction Modelling failure and predicting the strength of bonded joints is challenging due to various potential failure modes, especially with composite adherends, mixed-mode crack propagation, and plastic deformation. While analytical

* Corresponding author. Tel.: +351939526892; fax: +351228321159. E-mail address: raulcampilho@gmail.com

2452-3216 © 2026 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 Aleksandar Sedmak, Branislav Djordjevic, Simon Sedmak Dr. Simon Sedmak, ssedmak@mas.bg.ac.rs, Innovation Center of Faculty of Mechanical Engineering, Belgrade, Serbia 10.1016/j.prostr.2025.08.074