Molecular Dynamics Simulations Of Mechanical Properties Of Nanocomposites

The research of nano-materials is a hot subject now, such as the studies of nano-tube, nano-film and nano-composites et al. Nano-materials have some properties different from normal materials because of the nano-dimension. As one-dimensional nano-materials, carbon nanotubes(CNTs) have excellent mechanical, electrical, thermal and chemical properties because of hollow structure, a perfect hexagonal connection and quite high slenderness ratio. As a result, it has become the focus of researchers. Since the CNTs were added into polymer by Ajayan in 1994, the chemically modification and the compounding with polymer have caused widespread concern, which ask for the profound study.In this paper, functionalized CNTs, their composites and coating graphite/metal materials are studied using molecular dynamics (MD) method to simulate the mechanical properties of materials. The main contents are as follows:(1) Tensile and compressed properties of different functionalized CNTs are studied. According to the MD simulations of the extension process of functionalized CNTs for different densities, types and configurations, their influences on the mechanical properties are analyzed. According to the MD simulations of the compression process for different configurations, its influences on the buckling mode and critical buckling strain are analyzed. As a result, the high convergence of functionalized atoms results in better mechanical properties.(2) The Young's modulus and interfacial properties are studied by simulating the composites extension and the pulling-out process of CNTs. Some important conclusions are obtained as follows: Functionalization has little effect on the Young's modulus, but the maximum stress of composites significantly decreases. The higher convergence functionalized atoms are, the better mechanical properties the composites are. The axial forces of carbon atoms connecting with functionalized atoms are larger. Functionalization significantly enhances the interfacial adhesive properties, and the interfacial shear stress increases 20% for high convergence of the functionalized carbon atoms. At last, the pull-out processes of applying displacement to the end of CNTs are simulated. The axial forces of carbon atoms and interfacial shear stresses are obtained and compared with previous results.(3) The interfacial properties of coating graphite/metal materials are studied. Copper coating graphite/metal and nickel coating graphite/metal are simulated separately by imposing forces on the graphite. The energies of every part of models and every interface shear stress are obtained. The interfacial shear stress and the change of energy of nickel coating graphite/metal are larger than those of the copper coating graphite/metal. The results of simulations illustrate that nickel and graphite are well connected. The authors gratefully acknowledge the financial support of the Natural Science Foundation of China (No. 10872011) and the Natural Science Foundation of Beijing (No. 3092006)...