Enhanced mechanical interlocking of adhesive-bonded joints via tailored serrated patterns manufactured with laser ablation

Laser ablation is currently used as an effective alternative to mechanical or chemical surface pre-treatments for adhesive-bonded joints due to benefits in terms of adherend surface morphology and surface free energy. Several works have seen production of micro-scale textures on both metallic and polymeric substrates via 3D printing, while others have sought to modify the macroscopic topography by generating serrated profiles on adherends prior to joint assembly. In this work, laser ablation has been used to create micro-scale tooth-like interlocking features forming structured patterns with complementary profiles on aluminium adherends of single lap joints. In a first set of experiments, laser processing parameters were varied while an optical profiler was used to quantify the geometry of induced ablation craters and lines while assessing the distribution of re-melt in and around the exposed region. Subsequently, an ablation strategy was developed to achieve specific interlocking features. Finally, different symmetrical and asymmetrical patterns were generated for each pair of coupled adherends while differentiating the orientation of features with respect to the load direction. The results confirm the critical role that laser ablation plays in strengthening adhesive bonded-joints, with interlocking features providing additional benefits depending on the structure type and load direction.