Flow drill riveting of carbon fiber-reinforced polymer and aluminum alloy sheets

As a variation of friction stir blind riveting, flow drill riveting (FDR) is a new one-sided mechanical joining method for similar and/or dissimilar materials without predrilling holes on workpieces. In the FDR process, a blind rivet with a conical mandrel tip rotates at a high spindle speed and penetrates the workpieces due to local softening as a result of high friction between the mandrel tip and workpieces. The FDR process was applied to fabricating dissimilar lap-shear joints of 2.0-mm-thick carbon fiber-reinforced polymer (CFRP) and aluminum alloys (AA6061) with thicknesses of 1.0, 1.5, and 2.0mm in this work. The effects of the thickness of AA6061 and stack-up sequence of CFRP and AA6061 on the maximum tensile load and failure mode of FDR joints were analyzed and discussed. With the increase of AA6061 thickness, the maximum tensile load increased and the failure mode changed from failure at the AA6061 to failure at the CFRP disregarding their stack-up sequence. It is found that the maximum tensile load and the failure mode are strongly dependent on the relatively weaker one of AA6061 and CFRP workpieces, and the maximum tensile load of the FDR joint is closely related to its failure mode.