Mechanical characterization of interfaces in epoxy-clay nanocomposites by molecular simulations

Ultra high interface/volume ratio is an important feature of polymer-clay nanocomposites resulting from the nanometer scale dimensions of the clay particle. An understanding of the behavior of these interfaces on the molecular level is essential as they are largely responsible for the material propertiesof nanocomposites. In polymer-clay nanocomposites the concept of a binding energy is too simplified to be able to account for the presence of multi-phase interfaces. The gallery interface within intercalated clay particles and the interphase region with the polymer matrix are investigated. They are subjected to Mode I splitting deformation through molecular dynamics simulations and characterized by their traction-separation relationships. Several key parameters including peak strength, fracture energy and final splitting separation distances are qualified from the traction-separation curves which can be integrated into continuum models. The simulations reveal that the alkyl chain length of surfactants plays an essential role in the mechanical performance of these interfaces.