Macroscopic strength and failure properties of flow-drill screw connections

Abstract

Force–displacement responses and failure behaviour of connections using flow-drill screws to join aluminium sheets were investigated under various quasi-static loading conditions. This included single connector tests under tensile, shear and combined tensile and shear loadings, using cross test coupons in a new test set-up, and peeling and single lap-joint tests. The strength of the connection increased with the amount of shear loading, while the ductility decreased. No effect of the anisotropy of the sheets on the behaviour in the single connector tests was found. Axial crushing tests of aluminium single-hat sections joined with flow-drill screws were also performed. Two connection failure modes not observed during the single connector test were found in these tests. For comparison, equivalent single connector and component tests were carried out for self-piercing rivet connections. Similar trends with respect to the ductility, maximum force and shape of force–displacement curves were observed for the two connections, but the local failure modes were different.