Experimental and theoretical studies on laser treatment strategies for improving shear bonding strength of structural adhesive joints with cast aluminum

Surface physicochemical modifications induced by laser ablation treatment (i.e. rough morphology, removal of surface contaminants and newly-formed aluminum oxides) enhanced joint strength by 374% and improved the fracture mode from interface to cohesive. To acquire desirable joint strength with high processing efficiency, this study further investigates the influence of laser treatment strategies (i.e. distribution and area of laser-treated region) on shear bonding strength of structural adhesive joints with cast aluminum, which is also essential for industrial applications due to incomplete treatment of partial area in bonding region missing laser ablation inevitably occurring when processing complex part surfaces with variable curvatures. Therefore, four typical treatment strategies were designed by assigning laser-treated regions with various areas in different edges of adhesive bonding region, and analyzed through experimental and simulational studies. Moreover, comparative investigations show that the treatment strategy of assigning laser-treated regions on two bonding edges perpendicular to the loading direction more effectively improved the joint strength compared to the other three strategies, which is explained by an asymmetric M-shape distribution of interfacial shear stress from simulations. Furthermore, a theoretical model based on Goland-Reissner equation was established to predict joint strength in four treatment strategies with an overall error less than 10%.