Failure of carbon composite-to-aluminum joints with combined mechanical fastening and adhesive bonding

Composite-to-aluminum double lap joints were tested to obtain the failure loads and modes for three types of joints: adhesive bonding, bolt fastening and adhesive-bolt hybrid joining. A film type adhesive FM73 and a paste type adhesive EA9394S were used for aluminum and composite bonding. A digital microscope camcorder was used to monitor the failure of the joints. It was found that hybrid joining improves joint strength when the mechanical fastening is stronger than the bonding, as when the paste type adhesive is used. On the other hand, when the strength of the bolted joint is lower than that of the bonded joint, as when the film type adhesive is used, bolt joining contributes little to the strength of the hybrid joint.