Investigating the effects of number and distribution of GNP layers on graphene reinforced polymer properties: Physical, numerical and micromechanical methods

Experimental, numerical and micromechanical methods have been used to determine mechanical properties of graphene nanoplatelets (GNPs) reinforced epoxy resin. Tensile and compressive tests were performed on samples containing different GNP weight fractions. Experimental measurements showed an improvement in epoxy resin tensile and compressive mechanical properties with increasing GNP weight fraction. Also, Field Emission Scanning Electron Microscope (FESEM) was used to obtain images of the samples' fracture surfaces. These images suggested a good GNP dispersion in the matrix. Numerical simulations were carried out to investigate the effects of different geometrical parameters such as: number of GNP layers, GNP orientation, GNP distribution, and GNP/matrix interface on nanocomposite mechanical properties. Three different models containing one, two, and three layers of GNPs were analyzed to investigate the effects of number of GNP layers on nanocomposite properties. The GNP/matrix interface was modeled using several thin layers with different stiffness values surrounding the GNPs. The results of this investigation suggest that nanocomposite longitudinal modulus decreases with increasing the number of graphene layers. Also, the model consisting two layers of GNPs predicts values closer to experimental results. In addition, models consisting of GNPs oriented at different spatial orientations were analyzed to investigate the effect of GNP orientation on nanocomposite mechanical properties. It was observed that, GNP orientation significantly affects the nanocomposites elastic modulus. Moreover, Halpin-Tsai micromechanical model was used to estimate the nonlinear tensile stress-strain behavior of nanocomposites for randomly-distributed GNP nanocomposites. Finally, numerical and micromechanical results were compared and excellent correlation with experimental measurements was observed.