Effect of multiwalled carbon nanotube diameter on mechanical behavior and fracture toughness of epoxy nanocomposites

Abstract

Epoxy nanocomposites reinforced by multiwalled carbon nanotubes (MWCNT) with different diameters were prepared. The effect ofMWCNTdiameter on mechanical and fracture properties of epoxy nanocomposites were investigated. The results show that theMWCNTdiameter has an important influence on its dispersion performance. As theMWCNTdiameter increases, the dispersion performance becomes better. The reinforcing effect ofMWCNTson epoxy resins (EP) is affected by the combination of factors including the diameter and the additive amount ofMWCNTs as well as its dispersion. At low additive amount ofMWCNTs(.0.3 wt%), the reinforcing effect of MWCNTswith smaller diameter is better. However, as the additive amount ofMWCNTsincreases (.0.5 wt%), the reinforcing effect ofMWCNTswith larger diameters becomes more significant. MWCNTswith diameter of 25 nm(MWCNT-25) have the best reinforcing effect when the additive amount is 0.5 wt%, and the tensile strength and elastic modulus of the MWCNT-25/EP composites are increased by 11.5% and 8.3% than those of EP, respectively. The fracture toughness of the composites shows a tendency to increase first and then decrease with the increase ofMWCNT diameter. The main reason of this tendency is that the main failure mode ofMWCNTsgradually changes from fracture to pull-out with the increase ofMWCNTdiameter. The optimalMWCNT diameter is 25 nm, reaching the best toughening effect (KIC andGIC are increased by 38.8% and 80.9% than those of EP, respectively) at the additive amount of 0.7 wt%.