Hybrid effects in the fracture energy of nanocomposites

Abstract

This work aims to investigate the micromechanics of nanocomposites, with an emphasis on fracture energy. A broad analysis, with various matrices and nanofiller revealed that generally nanocomposite systems fail to meet their theoretical tensile strength and the elastic modulus, which were predicted by the micromechanics. Yet, the addition of nanofillers may significantly increase the fracture toughness. In this context, we investigated the fracture toughness of nanocomposites systems, and in these the specific cases of positive hybrid effect, the influence of nanofiller geometry and chemical structure and the mechanical behavior of nanocomposite system with a unique application. Hybrid nanocomposite materials comprise more than one type of nano-metric filler and may express a property which is higher than either the property of each one on the nanocomposites alone or of the arithmetic sum of their contributions – a positive hybrid effect. With the purpose of investigating the fracture toughness of nanocomposites, we examined three main systems, with various polymeric matrices (thermoplastic, semi-crystalline, thermoset) for diverse applications, and numerous nanofillers with different geometries and chemical structures, prepared by several methods. Therefore, this research deals with the fracture energy of hybrid nanocomposites, while taking a critical approach toward the currently prevailing engineering practice of applying classical composites micromechanics to nanocomposites.