Load-bearing capacity of hybrid riv-bonded aluminum-magnesium joints at quasi-static and cyclic loadings

The load-bearing capacity of hybrid riv-bonded aluminum-magnesium lap joints under shear-tensile loading was studied with particular focus on their static strength and fatigue performance. Sheets of 1.5 mm-thick EN AW6016-T4 aluminum alloy were joined with sheets of 2 mm-thick AZ91 magnesium alloy using two highstrength steel rivets and epoxy-based adhesive. Local deformation-induced fracture of the comparatively inductile magnesium alloy sheet at the rivet holes during riveting at room temperature was intentionally tolerated. The lap joints were heat-treated to peak-age the aluminum alloy (condition T4 -> T6) and to cure the adhesive between the sheets. Characteristic cross-section features and hardness maps were measured for assessing the quality of the joints and thus for proving the general capability of the riv-bonding process. The fracture behavior of the inductile magnesium alloy sheet determined the static strength as well as the fatigue performance at load ratios of 0.1 and 0.5. Both, load amplitude and mean load, influenced the site of fatigue crack initiation and the path of crack propagation. Local fracture of the inductile magnesium alloy sheet at the rivet hole is tolerable, if riv-bonded lap joints are just exposed to cyclic loading with low amplitudes.