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J.N. Reddy Mechanics of Carbon Nanotube based Composites with Molecular Dynamics and Mori-Tanaka Methods V. U. Unnikrishnan and J. N. Reddy Although carbon nanotubes (CNTs) are many orders of magnitudes stronger, stiffer, conductive, and lighter than the best available carbon fibers, the carbon nanotubes are required to be distributed homogeneously in the matrix and perhaps aligned in specific orientations to realize their effective properties in composite material systems. Though the basic principles appear similar to conventional fiber-reinforced composites (see J. N. Reddy, Mechanics of Laminated Plates and Shells. Theory and Analysis, 2nd ed., CRC Press, Boca Raton, FL, 2004), the scale of the conventional fibers in terms of µm is quite different from that of CNTs, which are in the order of a nano meter. This disparity in scales brings with it a new set of challenges. To achieve the promise of transferring the exceptional properties of the carbon nanotubes into practical devices, we need to understand how the processes that occur at the nanoscale affect those at macroscales ( µm to mm to m). This can only be achieved through a multi-scale modeling. The nanometer dimension of a CNT and its interaction with a polymer chain requires
a study involving the coupling of the length scales. The interaction of the molecules of
the CNT with the matrix creates an interphase with a reduced mobility and there
have been many attempts in predicting the overall bulk properties of such
nanocomposites. These studies were based upon idealizations applicable only in a
continuum framework. The investigation of mechanical behavior of nanostructure
materials is carried out with the Molecular Dynamics (MD) simulation using various
force fields for atomic structures. This interaction is subsequently idealized into an
Equivalent-Continuum (EC) model. With an EC model, the effective properties can be
obtained by Mori-Tanaka (MT) methods. In this lecture we discuss the modeling
aspects and variation of the effective properties of the CNT reinforced Poly-Ethylene
(PE) nanocomposite. The ultimate goal of this research is to provide a computationally
based multi-scale approach to realize the projected extra-ordinary properties of the
carbon nanotube-reinforced composites in structural applications of interest. |
