Design, manufacturing and testing of hybrid adhesive joints with metallic pins to join steel with fiberglass reinforced composite

Abstract

Traditional hybrid adhesive joints have been frequently used to join composite with metals as they provide a greater rigidity, higher failure stress than conventional mechanical bonding and a progressive ductile failure. However, this joining continues to require drilling the adherends and have got more weight than the adhesive bonds. A technical option that could improve the behavior of this bond is to use millimetric metal pins. Those pins are incorporated and distributed in the metallic material and, they are inserted into the composite material (before curing), during the assembly with adhesives. This type of hybrid joining has got more mechanical strength than equivalent adhesive bonding and absorbs more mechanical energy during breakage as a consequence of a non-abrupt failure mode. The mechanical behavior of this joint depends on the technique used to incorporate the pins on the metal substrate. In the present work, a manufacturing method has been developed for two types of double-overlap hybrid adhesive joints: with threaded pins and with wire pins, both are inserted into the metallic adherend. These manufacturing types are simple because they use economical conventional techniques, in contrast to other methods currently used. Joints reinforced with wire pins have shown a better mechanical behaviour since they have provided bond strength after adhesive breakage. Therefore, this system provides to the joint a safety mechanism against catastrophic breaks (due to premature failure of the adhesive) and, so, greater reliability.