Effect of Adhesive Geometry on the Tensile Properties of Aisi 1350 Steel

The use of structural adhesives in automotive industry is increasing steadily, as manufacturers become aware of the advantages that adhesives can offer, compared with the conventional techniques. However, not only the adhesive properties must be analyzed, the geometry must be taken into account as well 1 . It is theoretically and experimentally proved that, adhesive joints are more reliable than joints that are generated by conventional techniques such as screw bolt, rivet, welding, soldering, when designed according to working conditions. It is always possible to determine the strength values in the studies taking joint geometry, applied load type and direction into account 1 . Adhesive bonded joints can distribute load over a much wider area than mechanical joints. However, the design of safe and cost effective bonded joints is a major challenge. Engineers are required to have a good understanding of the influence of material and geometric parameters on the joint’s strength 2 . Good design practice normally requires that adhesive joints be constructed in such a manner that the adhesive carries the load in shear rather than tension since bonds are typically much stronger when loaded in shear rather than in tension across the bond plate. Lap-shear joints represent an important family of joints, both for test specimens to evaluate adhesive properties and for actual incorporation into practical designs. Generic types of lap joints that commonly arise are single lap, double lap, scarf, bevel, step, butt strap, double butt strap and tubular lap 3 . Joint behavior and joint strength depend on stress distribution over the joint. This stress distribution is influenced by joint geometry and the mechanical properties of the adhesive and adherents. The most significant parameters are: length of overlap, adherent thickness, adhesive thickness, adherent stress/strain behavior and adhesive strain/stress behavior 4 . The importance of adhesive joints was emphasized and it was argued the adhesives were alternatives to the other joint techniques. Especially, appropriate surface processing and adhesive selection was signified by Adams et al. 5 . Many studies have been done concerning the influence of adhesives on the mechanical strength of the joints both experimentally and numerically. The geome-