A simple and effective resin pre-coating treatment on grinded, acid pickled and anodised substrates for stronger adhesive bonding between Ti-6Al-4V titanium alloy and CFRP

Adhesive bonding between carbon fibre reinforced polymer (CFRP) and titanium alloy is extensively employed to achieve lightweight and adequate strength in aircraft structures. In this study, acid pickling, grinding and anodising treatments were applied to the Ti-6Al-4V titanium substrates, and the CFRPs were grinded to compare the performances. A special technique named resin pre-coating (RPC) was also used to improve substrate wetting. The single lap shear tests results showed that the bond strengths of grinded and anodised specimens were higher than that of the acid pickled specimens. The RPC treatment further increased the bond strengths of all the specimens by 29.9%–51.5% and appeared to be more effective on rough surfaces. A combination of the NaOH anodising and RPC treatment yielded the highest bond strength of 22.0 MPa, which was 105.3% and 70.1% higher than the bond strengths of acid pickled and grinded specimens, respectively, and the failure mode changed from adhesive failure to CFRP delamination failure. These surface treatments are simple and thus suitable for aerospace and aviation industries.