Microstructural origin of strength and toughness of epoxy nanocomposites

Nanocomposites of a bifunctional epoxy resin are synthesized and evaluated. Organically modified layered silicate (OLS) particles (4% by weight) and multiwalled carbon nanotubes (MWNT) (1% by weight) are used as reinforcements. Thermal and viscoelastic characterization of the two composites are performed and compared with the neat resin. Tensile tests are conducted on multiple identical unnotched and notched specimens to evaluate the overloading and fracture behavior of the nanocomposites. In comparison with the neat bifunctional epoxy, it is found that the 1% MWNT reinforcement increased the ultimate strength and strain to failure by about 139 and 158%, respectively. In comparison, the OLS has increased the ultimate strength and strain by about 30 and 20%, respectively. In comparison with the neat renin, there is a 170% increase in the fracture toughness of the MWNT composites and only 17% in the case of the OLS composites. Fracture surface analysis revealed the various mechanisms by which the MWNT composites acquire their superior strength and toughness in comparison with the neat resin.