Adhesive and composite failure prediction of single-L joint structures under tensile loading

In this article, single-L composite peel joints are investigated under tensile loading. The adhesive peel fillet is the critical component regarding joint failure, with sub-critical damage developing in the composite. Optimisation of the joint can be achieved by changing the fillet shape. A method of adhesive injection was applied to guarantee repeatable joint designs. Experimental testing shows an increase in joint strength of up to 100% by altering the fillet shape. Numerically, sub-critical composite failure, composite delamination and adhesive failure are investigated. Adhesive failure criteria are reviewed and compared to the experimental outcome. A zone criterion was found to predict the failure load best for different fillet shapes, while a damage mechanics approach could be applied to simulate the crack growth during adhesive failure.