Growing carbon nanotubes in-situ via chemical vapor deposition and resin pre-coating treatment on anodized Ti-6Al-4V titanium substrates for stronger adhesive bonding with carbon fiber composites

Adhesive bonding between titanium (Ti) alloy and carbon fiber reinforced plastic (CFRP) is extensively utilized to achieve lightweight and sufficient strength in aircraft structures. In this study, acid pickling, anodizing, heating treatments and chemical vapor deposition (CVD) method were applied to Ti-6Al-4V Ti substrates, and CFRPs were grinded to compare the performances. The resin pre-coating (RPC) technique was employed to improve void defects at the channel root of Ti substrate. SEM images indicated Ti substrates surface were covered by growing carbon nanotubes (CNTs) via CVD and epoxy resin was guided into channel root to reduce defects using RPC treatment. Single lap shear tests results exhibited adhesive bonding strengths of anodized composites were higher than that of acid pickled composites. RPC technique applied to Ti substrates after growing CNTs improved shear strengths by 22.3 % than adhesive bonding directly. The combined treatments of anodizing, CVD and RPC had the shear strength of 23.98 MPa improved by 123.5 % than that of acid pickling, which was higher and more stable than the one via external introduction of CNTs using RPC. The failure mode changed from adhesive failure to dominated cohesive failure. Therefore, the novel combined treatments are effective and suitable for aerospace industries .