Influence of the carbon nanotube type, loading and chemical functionalization on the fatigue resistance of aluminum lap joints

Abstract

Different types of carbon nanotubes (CNTs) with and without attached functional groups and with different loadings were used to prepare electrically conductive epoxy adhesive. By incorporating only 1 wt% of pristine single-wall CNTs the resistance of single lap joints (SLJs) was reduced by over 10 orders of magnitude compared to the neat resin. The type, loading and functionalization have little effect on the apparent shear strength of SLJs as the joints displayed mostly adhesive failure. Nanotube loading and functionalization have a strong influence on the fatigue life of the SLJs. Over 4 wt% of multiwall CNTs the fatigue life is only half of that of the neat resin. Repeated functionalization gradually decreases the length of nanotube pullouts and significantly increases the fatigue life. The tradeoff of improved fatigue life is a higher electrical resistance.