Through-thickness shape optimisation of bonded repairs and lap-joints

For realistic applications, the design of bonded repairs and lap-joints, has often been undertaken through trial and error finite element analyses, or experiment. Recent experience indicates that for more complex practical applications, unacceptably high adhesive stresses can occur in the adhesive layer. In the present work, an automated sensitivity-based shape optimisation procedure has been developed for the optimal design of free-form bonded repairs and lap-joints, with the aim of achieving reduced adhesive stresses. The approach has been demonstrated through application to a number of single and double-sided configurations where both the shapes of the adhesive layer and the outer adherend are allowed to vary. Significant improvements over conventional designs are obtained, as assessed by the reduction in peak adhesive stresses. These results indicate that the numerical shape optimisation procedures presented can provide designs that offer substantial improvements over standard designs.