Elastic interphase properties of nanoparticle/epoxy nanocomposites: A molecular dynamics study

The mechanical properties of nanocomposites are significantly influenced by interfacial interactions between nanoparticles and matrix. In this work, the elastic interphase properties of boehmite nanoparticle/epoxy composites are investigated using molecular dynamics simulations. The distinctive feature of this study is the characterization of the interphase properties thanks to the concept of atomic strain, which allows to capture the stiffness gradient at the interphase. The simulation results suggest that the size of the interphase region may not only be determined by the variation of the mass density, but also by an alteration of the polymer network structure close to the particle. A significant increase of the interphase stiffness is observed for a strong chemical bonding between boehmite and epoxy, while purely physical interactions lead to a slight reduction of the interphase stiffness compared to the bulk epoxy stiffness. Finite element analyses of representative volume elements of the nanocomposite show that the homogenized elastic properties are considerably influenced by the elastic interphase properties. The proposed simulation framework not only estimates elastic interphase properties of layered structures, but can be extended for studying the elastic properties of arbitrarily shaped contiguous subsections of molecular models.