Effects of clay structural parameters and gallery strength on the damage behavior of epoxy/clay nanocomposites

A computational model of a 3D representative volume element (RVE) for epoxy/clay nanocomposites is introduced to study their constitutive relationship and damage mechanisms. The model is composed of an epoxy matrix with embedded silicate layers. A gallery inter-layer is inserted between the silicate layers to mimic actual epoxy/clay nanocomposites. The predicted constitutive relationship and damage patterns of the epoxy/clay model with 3% weight fraction of nanoclay were in good agreement with experimental data and observation. It was found that some parameters of the clay particles such as the particle size and the number of silicate layers do not always affect the elastic stiffness or tensile strength of epoxy/clay nanocomposites. The model showed that when the gallery strength is larger than half that of the matrix, only matrix damage occurs. When the gallery strength decreases below this critical value, the tensile strength for the nanocomposites would decrease accordingly. This effect could possibly explain why experimental data for the tensile strength of epoxy/clay nanocomposites shows a large variation. By including an interphase layer between the epoxy matrix and clay particles, it was observed that the strength and damage patterns of the nanocomposites can change considerably with changes in the relative strength of the gallery and the interphase.