Investigation of the effect of surface roughness and plasma treatment on adhesively bonded aluminium-polyamide hybrid joints

This study investigated the effects of roughness and plasma treatment on adhesive-bonded aluminium and polyamide samples. The surfaces were treated using sanding and plasma methods, both independently and in combination. The results showed a slight decrease in contact angle and an increase in lap shear strength (LSS) with increasing surface roughness. The roughness of aluminium increased by 51.43 % (from 0.35 μm to 0.53 μm) and that of polyamide by 46.15 % (from 0.26 μm to 0.38 μm). This resulted in a 34.09 % increase in LSS (from 2.2 MPa to 2.95 MPa) specifically. Plasma treatment was then applied, which significantly reduced contact angles and enhanced LSS on both materials. However, amplification of these effects was not observed when treating both sides. The experiment showed a decrease in contact angle on aluminium by 47.88 % (from 71.77° to 37.41°) and on polyamide by 74.28 % (from 60.48° to 15.55°). Treating only polyamide resulted in a 105.42 % increase in LSS (from 2.95 MPa to 6.06 MPa). The optimal LSS was achieved by treating polyamide with plasma and increasing the roughness of both sides to around 50 %. The failure mechanism shifted from substrate to adhesion/cohesion due to plasma treatment. Additionally, an increase in roughness promoted adhesion failure.