Plasma treatment using nitrogen gas to improve bonding strength of adhesively bonded aluminum foam/aluminum composite

In this study, aluminum foam and aluminum plates were plasma-treated using nitrogen gas to improve the bonding strength of adhesively bonded aluminum foam/aluminum composites. Three types of test specimens were fabricated: (1) regular aluminum foam/aluminum, (2) regular aluminum foam/plasma-treated aluminum and (3) plasma-treated aluminum foam/regular aluminum. The treatment effect was determined by comparing the bending and shear strength of these three samples. Fractured surfaces of these specimens were investigated after bending and shear tests. The results showed that when the aluminum was plasma-treated, its bending strength and shear strength improved by 13 and 30%, respectively, compared to no plasma treatment. However, plasma treatment of aluminum foam produced a similar result to the case with no plasma treatment on aluminum. The plasma treatment did not induce a noticeable physical change in the surface, but it produced functional groups. It was judged that the improved bonding strength was caused by the aluminum's increased interfacial adhesion to the adhesive because the plasma treatment increased the surface's hydrophilicity.