Comparison of adhesive joint strength of laser fabricated dimple textured Al–Mg alloy in different environment

Abstract

Joining of aluminium alloys using adhesives has got tremendous applications in aviation, marines, and unmanned aerial vehicles. Surface preparation plays a crucial role in the adhesive joining of two surfaces. In this research work, the nanosecond fibre laser was used to create dimple-shaped textures on aluminium–Mg alloy (AA5754). Dimple-shaped textures were created under three different atmospheric conditions. Experiments were performed in open-air conditions, under static water conditions, and under flowing water conditions. Texture depths differed by varying the scanning speed of laser beam. Texture pitch was also varied at two different levels, that is 300 [Formula: see text]m and 400 [Formula: see text]m in both texturing directions. Two different scanning speeds of 2.5 and 5 mm/s of the laser beam were investigated. Surface contact angle of each sample was evaluated using a goniometer to measure surface hydrophobicity/ hydrophillicity. Surface roughness and dimensions of dimples were measured using a digital microscope. Scanning electron microscopes were used to evaluate the morphology of textured surfaces. An epoxy-based adhesive (partite) was uniformly spread over textured zones and samples for standard tensile tests were prepared as per ASTM. Shear lap tensile tests were carried out to evaluate the shear lap strength of each joint on a universal testing machine. Surfaces prepared in static water conditions and flowing water conditions resulted in completely different morphology compared to open-air processing. It was observed that dimple patterns fabricated under flowing water conditions had the highest bonding strength among all the three processing environments.

Surface Treatments for Enhancing the Bonding Strength of Aluminum Alloy Joints

“…Zhu et al [ 29 ] ulteriorly studied the effects of laser power on the bonding performance of aluminum alloy formed by sheet, extrusion, and cast, respectively. Several similar works referring to the effects of laser parameters on shear strength [ 30 , 31 , 32 , 33 ] and fracture behavior [ 34 , 35 ] claimed that laser ablation could significantly affect wettability and bonding performance. Prakash [ 34 ] emphasized that the dimensions of dimples including texture depth and pitch were the key factors to the bonding strength, but the effect of the texture was not examined.…”

“…Several similar works referring to the effects of laser parameters on shear strength [30][31][32][33] and fracture behavior [34,35] claimed that laser ablation could significantly affect wettability and bonding performance. Prakash [34] emphasized that the dimensions of dimples including texture depth and pitch were the key factors to the bonding strength, but the effect of the texture was not examined. Some works around the technological parameters of laser ablation have been performed, while more complicated issues on geometrical parameters of surface textures fabricated by laser ablation need to be clarified.…”