The effect of temperature on the mechanical properties of adhesives for the automotive industry

The application of adhesively bonded joints in structural components made of composite materials for automotive industry applications has increased significantly in recent years and provides many benefits that will ultimately lead to lighter-weight vehicles, fuel savings, and reduced emissions. The principal benefits are design flexibility, opportunity for part consolidation, and joining of dissimilar materials. While much work has been conducted in adhesive bonding for the aerospace industry, the automotive industry does not currently have a full portfolio of processes and methods for evaluating candidate adhesives for use in bonding structural automotive components. Aerospace techniques and materials are not generally applicable, since the automotive industry must be more cognizant of cost and high volume production. In this article, the performances of two different adhesive types, an epoxy and a polyurethane, have been studied through bulk specimen and adhesive joint tests. Results showed that the failure loads of both the bulk test and joint test specimens vary with temperature and this needs to be considered in any design procedure. Also, for the polyurethane adhesive, the single lap joint is sufficient to determine the adhesive shear strength.