Adhesive joint design methods and examples

Abstract

Challenges of reliable prediction of resistance of bonded joints lie in the complexity of stress concentrations, multiple crack paths, mode-mixity and sudden crack propagation. The new Technical Specification for Design of fibre-polymer composite structures (TS) is bridging this gap by providing comprehensive sets of design recommendations and analyses to be used for the verification of adhesive joints. Two design approaches in the TS, based on stress analysis and fracture mechanics, are summarized and basic design assumptions on allowed failure conditions and partial factors in relation to execution and maintenance are highlighted. The application of the design recommendations is shown on the example of determining the design value and the ultimate resistance of a simple double lap joint. FE models built in Abaqus are used to analyse stress concentrations and crack initiation and propagation based on material level experiments. Variability of the material properties are taken into account through partial safety factors. Joint resistances obtained by the stress-based approach and fracture-mechanics approach are compared.