AA6063-T6 (Al-Mg-Si-Fe) based similar and dissimilar T-joints: effects of joint configuration and stringer material on load-bearing capacity and free vibration characteristics

Joining aviation-grade Al alloy with similar high-strength metal or glass fiber reinforced thermoplastic is one of the hot topics in many engineering applications especially in aerospace industry. As out-of-plane joints, T-joints, where the loads are transferred at 90°, are very sensitive to mechanical loads, and their vibration response should be carefully investigated. Therefore, this paper presents a comprehensive investigation on tensile-shear properties and vibration behavior of metal-metal and composite-metal joint structures bonded in two different configurations through structural epoxy adhesive. T-joints, which consist of a stringer and a base plate, also undergo assessment based on the influence of stringer position in the joint on the vibration characteristics. The results indicate that the laser ablation treated surfaces exhibit superhydrophilicity through the surface energy increment. Using L-shaped stiffeners instead of a groove increases the strength, whether similar or dissimilar joints. Compared to an adhesive failure, mixed mode failure is observed for the Al-Al-Stiffener joints. The change of stringer material to composite also leads to reduced second natural frequencies and increased damping ratios for the second mode.