Reinforcement study of anodizing treatment with various temperatures on aluminum substrates for stronger adhesive bonding with carbon fiber composites

Aluminum alloy and carbon fiber reinforced plastic (Al-CFRP) composite are usually applied to the lightweight design and manufacture of important field equipment due to the lightweight and high strength. However, the high performance and industrialization of Al-CFRP composites are restricted by degumming issues caused by poor wetting and compatibility, and weak mechanical occlusion of bonding interface between epoxy resin and substrates. In this study, anodizing treatments with three temperatures were employed to etch Al substrate surface for various pore structure, CFRP panels were grinded to create a strong CFRP/epoxy bonding interface to compare the performances changing resulting from treatments on Al substrate surface. Resin pre-coating (RPC) technique was used to eliminate the originally existing defect caused by macromolecular epoxy at the root of porous Al substrate in common adhesive bonding. The carbon nanotubes (CNTs) were utilized to improve the bonding interfaces and adhesive layers. The single lap shear results showed the best shear strength of anodized specimen at 30 °C was up to 23.4 MPa improved by 268.9 % than base. Failure modes exhibited the weaker debonding failure at Al/epoxy interface was converted into dominated fiber fracture and delamination failure of CFRP after combined surface treatments. These results indicate associative treatments of anodizing at 30 °C and CNTs-contained RPC are effective and contribute to developing a solution in industrial application of high-performance Al-CFRP composites.