Single-walled carbon nanotube–epoxy composites for structural and conductive aerospace adhesives

Single-walled carbon nanotubes (SWCNTs) were incorporated at low loading (up to ∼1wt%) into an unfilled aerospace-grade epoxy system, to impart electrical conductivity while maintaining structural bonding capability, as a route for development of a structural and conductive adhesive. At these low SWCNT loadings the tensile properties were maintained or improved, while strength decreased in a higher loading case. The structural bonding performance of composite-to-composite joints, evaluated in lap-shear and peel tests, was reasonably maintained for adhesives containing 0.5wt% or 1wt% SWCNTs. In the case of the 0.5wt% SWCNT–adhesive, peel and lap-shear strength were unchanged while the addition of 1wt% resulted in 30% increase of peel strength but the lap-shear strength was reduced by 10–15%. For 1wt% SWCNT–adhesives, conductivities as high as 10−1Sm−1 and typically ∼10−3Sm−1 were achieved. Joint electrical resistance measured between aluminum adherends was larger than predicted by the bulk conductivity, but was reduced by a post-treatment step resulting in apparent joint conductivities within one order of magnitude of the bulk samples.