EVALUATION OF THE JOINT BASED ON DIFFERENT SURFACE CONDITIONS FOR ALUMINUM-POLYAMIDE LASER WELDING

Laser welding is one of the most promising joining techniques to realize hybrid joints between metals and polymers in order to achieve
weight reduction and functionalization of the parts. The surface treatment of the metal has a decisive effect on the joint quality and thus on
the mechanical properties. In the present study, different mechanical and laser-based surface treatments have been investigated to develop
diverse surface conditions on aluminum. Abrasive blasting and laser ablation were used to increase the surface roughness, while abrasive
polishing and laser polishing were applied to minimize the surface roughness. In contrast to abrasive surface treatments, laser-based ones
were implemented to create artificial oxide layers on the aluminum surface. The surface structures of pretreated samples have been studied
with scanning electron microscopy and roughness test. The laser welding of pretreated aluminum with polyamide was achieved with the
heat conduction joining technique. To enlarge the welding area and control the heat input, spatial and temporal modulations of the laser
beam were implemented. Finally, a single lap tensile-shear test, microscopic analysis of fractured surfaces, and welding cross sections were
employed to evaluate the joints. Results show that the presence of an artificial aluminum oxide layer and low roughness are essential to
achieve a superior joint between aluminum and polyamide (improvement of approximately 58% in the shear load of the joint compared to
as-received welded samples). The cross section of the superior joint which is the laser-polished aluminum welded to polyamide is studied
with transmission electron microscopy.