Effect of Loading and Surface Modification of MWCNTs on the Fracture Behavior of Epoxy Nanocomposites

Nanocomposites consisting of multiwalled carbon nanotubes (MWCNTs) and a bifunctional epoxy resin are manufactured by a unique dispersion technique. The effect of loading and surface modification of the MWCNTs on the mechanical properties and fracture behavior of the nanocomposites is studied. Both a scanning electron microscope (SEM) and an atomic force microscope (AFM) are used to identify the mechanisms by which the nanocomposites acquired their fracture resistance. At 0.1 wt% loading, both ball-milled and acid-treated MWCNT composites perform better than the neat resin. An increase of 40% in the fracture toughness has been achieved at 0.15 wt% loading with ball-milled MWCNTs. An increase of 80% in the fracture toughness has been achieved at 0.15 wt% loading in the acid-treated MWCNT nanocomposites. The AFM images of the MWCNT nanocomposites reveal that the MWCNTs are well dispersed in both the systems. A better dispersion of MWCNTs has been achieved with acid treatment than with ball milling. The SEM images of the fractured surfaces reveal a tremendous increase in the number of fracture surface features associated with the acid-treated MWCNT nanocomposites, in comparison with the ball-milled MWCNT nanocomposites and the neat resin.