Role of Graphene Sheet Agglomeration in the Macroscopic Elastic Properties of Metal Matrix Nanocomposites

The purpose of the present work is to analyze the modulus of elasticity of graphene (Gr) sheet-reinforced metal matrix nanocomposites (MMNCs) using a homogenized model based on the Mori-Tanaka micromechanics approach. The main focus is to investigate the effects of Gr sheet agglomeration on the MMNC macroscopic elastic modulus. Also, the role of aligning Gr sheets in the mechanical performance of MMNC is explored. It is found that a small amount of Gr sheets can increase the elastic properties of the MMNCs. Addition of 5% by volume fraction of Gr sheet in an aluminum (Al) matrix improves the MMNC elastic modulus by 31%. The mechanical properties of MMNCs are very sensitive to the Gr sheet agglomeration. Formation of sheet agglomeration can significantly decrease the MMNC elastic modulus. It is observed that the Gr sheet alignment plays a superior role in enhancing the MMNC elastic properties. Generally, alignment of Gr sheets leads to the maximum level of MMNC mechanical properties in axial direction. As compared to the uniform dispersion type, aligning the 5 vol% Gr sheets can improve the elastic of Al nanocomposite by as much as 20%. The elastic modulus calculated from the present micromechanical model for different types of MMNCs is compared with available experimental data. In addition, the results from the Mori-Tanaka method are also compared with other analytical results acquired from semi-empirical Halpin-Tsai (H-T) model and the rule of mixture (ROM).