Effect of Surface Roughness on Shear Strength of Bonded Joints of Aluminum AL 6061 T6 substrate

Abstract

In this study, effect of surface roughness on adhesive bonding of aluminum (AL 6061 T6) substrates is investigated to determine the required bond strength between the adhesive and adherends interface. Quality of AL 6061 T6 lap shear joints (adherend surface preparation) is achieved by mechanical abrasion using diverse grades of silicon carbide sheets (P 320C, P 220C and P 180C). Lab grade acetone is utilized for the removal of impurities from the substrate surface while Loctite 4090 is served as adhesive to bond lap shear joints. Surface roughness of the substrates is measured by using profilometer (SURFTEST SJ-210). Experimental testing of adhesively bonded specimens with diverse surface roughness is conducted on Universal Testing Machine (UTM) to measure the shear strength. The results show that, aluminum adherends pretreated with P220 C achieve maximum adhesion bond strength up to 34.45 MPa at surface roughness of Ra=1.55 µm, but further increase in surface roughness from Ra=1.55 µm to Ra=2.4 µm causes 13.7% decrease in shear bond strength. Furthermore, the specimens without pretreatment achieve minimum shear bond strength up to15.23 MPa at surface roughness of Ra=0.03 µm. It was concluded that with the increase in surface roughness of the adherends up to certain limit, bond strength also increases, and locus of failure shifted from adhesive - adherend interface to within the adhesive.