Epoxy composites with 200 nm thick alumina platelets as reinforcements

Composites were prepared by dispersing Alumina platelets of polygonal shape having a thickness of 200 nm and size of 5–10 lm in epoxy (LY 556) matrix using sonication. Good dispersion of the platelets was observed through scanning electron microscopy (SEM). The quasi-static plane-strain fracture toughness and tensile properties of the composites were determined for platelet volume fraction varying from 0% to 10%. The results indicated that addition of the platelets give considerable improvement in fracture toughness and good improvement in the elastic modulus of epoxy. For 10% volume fraction of the platelets, the fracture toughness improved by 110% where as the improvement in elastic modulus was 78%. However there was an associated reduction of 53% in tensile strength and 73% in failure strain. SEM of fractured surface was carried out to understand the various mechanisms responsible for the improvement in fracture toughness. By appropriately accounting for the orientation and stacking effects of the platelets, the applicability of predictive models, such as the Halpin-Tsai and Mori-Tanaka, for estimating the composite modulus is demonstrated.