Elastic properties characterization of fully exfoliated polymeric nanocomposite using finite element method

In this paper, the elastic properties of fully exfoliated nanocomposite are investigated using the finite element method (FEM). First, a three-dimensional cubic model, as known representative volume element (RVE), is conducted to simulate the dispersion of particles inside the matrix using Matlab. The nanosheets are considered as rectangular cubes with a length of 100 nm and a thickness of 1 nm. Also, the size of the RVE edge is about four times the size of the particle length. Then, this model is transferred to the FEM environment and meshed using three-dimensional elements. Since the interphase region is one of the important and effective parameters on the mechanical properties of nanocomposites, it is modeled as a layer with nanometer thickness on the filler. The elastic properties of the interphase region are predicted by presenting an exponential function. The properties of the matrix, filler, and interphase region are applied to different parts. The matrix and filler are respectively Naylon6 and nano clay. In this type of nanocomposite, an fully exfoliated structure is observed. Finally, by applying boundary conditions and force in different directions, the elastic modulus and Poisson s ratio of nanocomposite are calculated at different volume filler percentages between 0-2%. The results show that the elastic modulus in three RVE directions are close to each other, indicating a suitable dispersion of particles in different directions. The elastic modulus of composite at 2% volumetric increases by about 1.5 times compared to matrix. Also, by increasing the percentage of filler, Poisson s ratio of composite decreases to some extent. The results show that the interphase region has a very significant effect on the elastic modulus of composite and by increasing the modulus or thickness of this part, composite gains more strength. To verify, numerical results are compared with analytical two-phase model Halpin-Tsai. Comparison of numerical results with Halpin-Tsai model shows that numerical results are closer to experimental results reported literature. The reason for this issue can be as follows: The numerical model is three-phase and considers the interphase region. While in Halpin-Tsai model, two phases of matrix and filler are considered. The second reason can be more accurate geometry of filler than Halpin-Tsai case. In numerical model, exact geometry of filler is applied, while in Halpin-Tsai model only aspect ratio of filler is considered which increases error prediction of model. Finally, it can be said that by using this method, mechanical properties of different composites with plate-shaped filler can be well predicted which plays an essential role in designing composites.