Corrosion and environmental degradation of bonded composite repair

Abstract

PurposeBonded composite patches are ideal for aircraft structural repair as they offer enhanced specific properties, case‐tailored performance and excellent corrosion resistance. Bonding minimizes induced stress concentrations unlike mechanical fastening, whilst it seals the interface between the substrate and the patch and reduces the risk of fretting fatigue that could occur in the contact zone. The purpose of this paper is to assess the electrochemical corrosion performance and the environmentally induced mechanical degradation of aerospace epoxy adhesives when carbon nanotubes (CNTs) are used as an additive to the neat epoxy adhesive.Design/methodology/approachThe galvanic effect between aluminium substrates and either plain or CNT enhanced carbon fibre composites, was measured using a standard galvanic cell. Also, rest potential measurements and cyclic polarizations were carried out for each of the studied systems. The effect of the CNT introduction to a carbon fiber reinforced plastic (CFRP) on the adhesion efficiency, before and after salt‐spraying for 10, 20 and 30 days, was studied. The adhesion efficiency was evaluated by the single lap joint test.FindingsThe corrosion behaviour of the system is polymer matrix type dependent. CNT introduction to a CFRP may induce small scale localized degradation.Originality/valueThis paper fulfills an identified need to study how the shear strength and the response to galvanic corrosion are affected by epoxy resins modified by carbon nanotubes.