Influence of the temperature cycle on local distortions in car panels caused by hot curing epoxies

Adhesive bonding is becoming a more and more important joining technology in automotive industry. Hot curing epoxy adhesives are often used for structural bonds of car body shells. The cure process of the adhesive, however, can cause panel surface distortions. These distortions can occur close to the bond-line (local distortions) or concern the whole geometry of a part (global distortions). In order to avoid these defects, a fundamental understanding of how distortions develop is needed. In this work, the development of distortions is monitored over entire temperature cycles by means of a displacement measurement. The focus is on how different cure temperatures and heating rates affect the development and the final state of local distortions. It was found that distortions can already develop in the heating phase before the cure temperature is reached. Changes in the heating rate influence the development of distortions.