Micromechanics of nanocomposites

The enhancement in fracture toughness of polymers can be obtained by introducing of CNTs, graphene, NCs and nanosilica. The optimized toughness can be achieved by incorporation of proper size, type and amount of nanofillers, which in turn determine the energy dissipating interaction of the crack front with the nanoparticles. The homogenous dispersion of nanofillers in the polymer resin is essential to achieve the optimal mechanical performance of the nanocomposites. Two distinct methods, i.e., mechanical dispersion and surface functionalization are usually used for the dispersion of nanofillers. CNTs showed good toughening effects at low loading (0.1–1.0 wt%). Above 1 wt%, high viscosity of the systems hindered the dispersion of CNTs, causing the formation of the agglomerates. Compared with CNTs, the studies on graphene demonstrated a better toughening effect at very low loading (under 1 wt%). In the case of NCs and nanosilica, the toughening effect was inferior compared with CNTs and graphene and an enhancement in fracture toughness was only observed at much higher loading (1.0–20 wt%).