Experimental and numerical analysis of hybrid adhesively-bonded scarf joints

Adhesive joints have been largely used in many areas such as automotive and aeronautic industries, navy, electronic components and construction, among others. The increased application of this joining technique is due to an easy manufacturing, lower costs, easiness to joint different materials, more uniform distribution of stresses and higher fatigue strength. The scarf joint is one of the possible joint configurations and it excels in not requiring to change the initial shape of the component. Improved stress distributions over single and double-lap joints are obtained, although it has some complexity in the manufacturing process. In many practical applications, joining between different adherend materials is required due to design constraints, which poses additional difficulties because of the different stiffness of the materials. This work presents an experimental and numerical study on hybrid scarf joints, between composite and aluminium adherends, and considering different scarf angles (alpha) and adhesives (the brittle Araldite(center dot) AV138 and the moderately ductile Araldite(center dot) 2015). Comparison with joints having material balanced adherends is also performed numerically. The numerical analysis by Finite Elements (FE) enabled obtaining peel (sigma(y)) and shear (tau(xy)) stresses using the software Abaqus(center dot), which are then used to discuss the strength between different joint configurations. Cohesive Zone Models (CZM) were used to predict the joint strength and the results were compared with experiments for validation. A significant variation of the joints' behaviour was found depending on a and the applied adhesive, which was directly linked to the stresses developed in the adhesive layer during loading. CZM were found to be an accurate design tool for the hybrid scarf joints.