Effect of surface morphology characteristic parameters on the shear strength of aluminum bonded joints

To understand the effect of surface morphology on the shear strength and failure mode of single-lap joints with micron-thickness bondline, sandblasting and phosphoric acid anodizing (PAA) methods were used to treat the surface of the 2A12 substrates. Compared with the original milling surface, the Ra values of the sandblasting surface increased by 7–10 times, but the peak count number (Rpc) reduces by 20%–50%, which made the sandblasting surface “smoother” in micron- or nano-scale. The PAA method has slight effect on the Ra, Rz, and Rpc values in micron-scale, while it can generate a porous anodic film and change the morphology in nano-scale. For the sandblasted surface, the shear strength first slightly increases with the increase of the Ra value but then decreases due to the decrease of Rpc. For the micron-level bondline, the surfaces treated by the PAA method show much higher shear strength and a greater degree of cohesive failure than those only by the physical methods.