Comparison of novel surface treatments of Al 2024 alloy for al/cfrp adhesive bonded joints

The objective of this study is to investigate the effect of silane and fiber laser treatments on the shear strength and failure type characteristic ofAA2024-T3/unidirectional carbon fiber-reinforced epoxy composite [0](8) laminates (Al/CFRP) adhesively bonded joints. Epoxy-based paste 2 part adhesive (Loctite EA 9396 AERO) was used for adhesive joining. Chemical surface treatment was tested with three different silane concentrations (1, 3 and 5 vol %) applied to AA2024-T3 aluminum plates after cleaning. In addition, 50 W pulsed fiber laser was used to AA2024-T3 aluminum plates for laser treatment. For determining the optimum fiber laser parameters (laser power, frequency and scanning speed) L9 orthogonal array Taguchi method (3 variables and 3 levels) was used. The chemical composition of the fiber laser and silane treated AA2024-T3 sample's was analyzed using Fourier transform infrared spectroscopy - attenuated total reflectance (FTIR-ATR). Shear strength values of the Al/CFRP bonded joints were determined by using single lap shear tests. From the test results, the silane concentration of 3 vol% on AA2024-T3 aluminum plates had a significant effect on shear strength of Al/CFRP bonded joints (16.44 MPa) compared to untreated samples (6.46 MPa). In addition, it was determined that the laser treating parameters of scanning speed of 100 mm/s, frequency of 80 kHz and power of 50 W laser power achieved the optimum surface of AA2024-T3 to be strongly bonded with CFRP (23.68 MPa). After mechanical tests, failure modes were also observed by using the digital camera.