Shape optimization of adhesives of multi-materials under multiaxial stress failure criteria

The concept of multi-material design has been applied in many industries in recent years. Among various methods of joining dissimilar materials, adhesive bonding has the advantage of being low weight. It is necessary to understand the failure criteria of adhesives in choosing the most preferable adhesive for improving the strength of a bonded structure. Experiments using pipe specimens with inclined surfaces bonded by epoxy adhesive were performed, whereby multiaxial stress states were realized simply by conducting a uniaxial tensile test. The failure function of the epoxy adhesive, expressed by the mean stress and octahedral shear stress, was then obtained from the experimental data and compared with that of acrylic adhesive previously reported in the literature. The obtained failure functions of both adhesives were then applied to the shape optimization of the adhesive layer under different loading conditions. The optimization object is the strengthening of bonded structures. The optimal shape for different loading conditions differed for the different adhesives because of the driving force generated by the applied stress. The final shapes were thus optimized numerically to attain the highest mechanical integrity of the adhesive layer and found to be strongly dependent on the initial shapes before optimization.

Automated summary

The concept of multi-material design has been widely used in various industries, and adhesive bonding is a favored method due to its lightweight advantage. This study compares the failure functions of epoxy adhesive and acrylic adhesive, and applies them to the shape optimization of the adhesive layer under different loading conditions to improve the strength of bonded structures.