These slides were presented at the NAFEMS World Congress 2025, held in Salzburg, Austria from May 19–22, 2025.

Abstract

The demand for lightweight structures is seeing an increasing trend, driven by the transition towards more sustainable ways of transportation and the imperative to reduce emissions and fuel consumption. Adhesive joints and hybrid joints, which combine adhesive bonding with traditional joining techniques such as spot welding and riveting, are emerging as a viable solution for achieving lightweight components. These joints are gaining traction in the transportation sector due to their ability to leverage the benefits of each joining method. To enhance the design of adhesive and hybrid joints and mitigate the risk of fatigue failures during service, the transportation industry requires efficient, robust, and user-friendly methods for modelling and estimating the fatigue life of these joints. The fatigue performance of hybrid joints is affected by various factors, including the material, thickness and surface preparation of the adherends, the type of adhesive and, in the case of hybrid joints, the type, size, and quality of the mechanical fasteners. Consequently, it is advisable to derive custom Stress-Life (SN) curve parameters from tests on adhesive or hybrid joint specimens that accurately represent production joints. This study introduces a pragmatic approach for estimating the fatigue life of adhesive and hybrid joints between metals, which can be readily implemented by companies in the transportation industry. The proposed approach includes Finite Element (FE) modelling strategies and recommendations to obtain the necessary stress data with minimal modifications to existing FE modelling practices commonly used in the automotive industry. These strategies ensure that the FE models are computationally efficient, exhibit low mesh sensitivity, and do not require congruent meshes. Additionally, the method encompasses fatigue analysis and life estimation of adhesive and hybrid joints between metals using a Stress-Life (SN) based analysis tool. Finally, it includes a testing and data analysis framework to generate custom SN curves suitable for use in analysis. The generation of custom SN curves is also demonstrated using real test data obtained as part of an extensive testing programme on metal lap-shear and coach-peel hybrid joints with different types of mechanical fasteners.