Effect of Laser Processing Pattern on the Mechanical Properties of Aluminum Alloy Adhesive Joints

Adhesive bonding is a promising joining technology for joining lightweight aluminum structures, offering advantages such as the absence of additional heat input, connection damage, and environmental pollution. To further enhance the strength of aluminum adhesive joints, this study investigates the influence of laser surface treatment on their mechanical properties. Specifically, the effect of laser processing patterns and their geometric parameters on aluminum alloy adhesive joints is examined. A fiber laser is used to process crater array and multi-groove pattern on A6061 aluminum surface. The impact of crater overlap ratio and groove distance on various aspects, including aluminum surface morphology, roughness (S_a), adhesive joints shear, tensile strength, and failure modes is discussed. Laser confocal microscope tests, water contact angle tests, lap shear tests, and cross tensile tests are employed to analyze these parameters. The results indicate that as the crater overlap ratio increases, the S_a value of the aluminum surface increases. Moreover, the shear strength of adhesive joints initially increases and then decreases, while the tensile strength consistently increases. On the other hand, an increase in groove distance leads to a decrease in S_a, as well as a reduction in both shear and tensile strength of adhesive joints. For shear loading conditions, mechanical interlocking is identified as one of the bonding mechanisms in aluminum adhesive joints featuring crater array and multi-groove patterns. The formation of interlocking structures is found to be influenced by the aluminum surface pattern and its associated parameters, as revealed through failure surface analysis. Specifically, adhesive and crater or groove interactions contribute to the formation of interlocking structures in specimens with a crater overlap ratio of − 60% or groove distances of 120, 180, 300, and 400 μm. Conversely, specimens with overlap ratios of 0%, 40%, and 60% exhibit interlocking structures formed by the adhesive and crater edge.