Study on the interface and failure characteristics of joints between epoxy adhesive and duralumin alloy

In the realm of optomechanical joints, the roughness of the component frequently limits the bonded joint's stability and dependability. This study investigates the failure mechanisms and interfacial stress transfer characteristics of bonded structures with six controlled roughness levels to elucidate roughness-dependent adhesion behavior. Shear experiments have been carried out to analyze the failure mechanisms of bonded joints. The results indicate that when roughness increases, shear strength first rises and subsequently falls. When the surface roughness of the duralumin alloy is 4.2 ± 0.75 μm, the shear strength reaches its maximum value of 11.97 MPa. After analyzing the surface characteristics of substrates with various degrees of roughness, the results show that increasing surface roughness can significantly change the substrate's surface energy, wettability, and contact area while also greatly changing the bonding quality. The fractographic evaluation identified interfacial debonding and cohesive-adhesive hybrid failure as the predominant fracture mechanisms. Specimens exhibiting hybrid failure demonstrated enhanced interfacial load transfer capability through synergistic contributions from both adhesive-substrate bonding and bulk adhesive deformation. This research offers an important reference for the manufacture and application of epoxy adhesive and duralumin alloy joints. It has a guiding significance for improving the performance and reliability of joints.