Effect of adding method of carbon nanotube on interlaminar property of carbon fiber/epoxy composites

The carbon fiber/epoxy prepregs modified by carbon nanotube (CNTs) were prepared by two methods, including directly dispersing CNTs in resin and spraying CNTs on surface of the prepregs. Mode I and mode II interlaminar fracture toughness as well as interlaminar shear strength of CNTs-carbon fiber/epoxy composite laminates fabricated by the two different prepregs were evaluated. The viscosity, curing reaction and glass transition temperature of resin were investigated to analyze the influences of CNTs content on resin properties. The length and morphology of CNTs in the two different methods were also compared. The modification effects and reaction law of adding CNTs methods on the interlaminar fracture toughness and interlaminar shear strength were discussed. The results show that the introduction of CNTs in resin causes an increase of resin viscosity and the reduction of curing reaction degree. These two methods have no significant effect on length and morphology of CNTs. For mode I, II interlaminar fracture toughness and interlaminar shear strength of CNTs-carbon fiber/epoxy composite, the improving degree from directly dispersing CNTs in resin is smaller than that from spraying CNTs on surface of carbon fiber/epoxy prepregs. The latter method has high utilization efficiency of CNTs. Moreover, high content of CNTs causes a decline of the toughening effect, resulting from CNTs aggregation and the effect of CNTs on resin curing reaction.