Enhanced bonded aircraft repair using nano-modified adhesives

The scope of the present work is to investigate if the introduction of a small weight fraction of multi wall carbon nanotubes (CNTs) in a polymer adhesive film can: (a) act as an effective corrosion barrier that inhibits access of the electrolyte to the surface of the aluminium substrate thereby preventing or notably delaying destructive localised aluminium corrosion, (b) lead to a hybrid system with galvanically compatible constituents and (c) enhance the adhesion of the film to the alloy substrate. Electrochemical measurements showed that the incorporation of CNTs into the epoxy film does not mediate the galvanic effect between substrate/coating, whilst it introduces limited localised degradation phenomena into the polymer matrix. However, it reduces the uniform corrosion rate of the film. Lap shear testing showed that the adhesion enhancement that stemmed from CNTs doping was significant in the absence of anodising of the substrate. It is proposed that a bi-layer patch, where the intermediate layer will be the neat polymer film and the over-layer will be the CNTs-reinforced film would be beneficial in terms of optimising the anodic protection by the patch and the galvanic compatibility of the alloy substrate/patch system.

► Carbon nanotubes mixed in structural adhesives improve adhesion on aluminium.
► Carbon nanotubes may be employed to tailor the galvanic behaviour.
► Carbon nanotubes can enhance bonded repair of aircraft aluminium structures.