Determination of Elastic and Thermal Properties of Nanocomposites by Fiber Embedment in Finite Elements
P.D. Spanos, M. Esteva, J.E. Akin
Rice University, US
Keywords: carbon nanotubes, nanocomposites, modeling, entangled fibers, Monte Carlo, finite elements, distributions
Abstract:In this paper the impact of entangled and non-straight fibers in the determination of the effective elastic and thermal properties of polymer nanocomposite (PNC) is addressed. Most of the models in recent studies assume nanotubes to be well dispersed straight fibers with fixed size. Nonetheless experiments reveal that nanotube formation become wavy during the manufacturing process, and that nanotubes come in a variety of diameters and lengths. In the paper an attempt to model the behavior of entangled fibers is made in which the distributions regarding the nanotube length and diameter are incorporated. First, an approach to generate random microstructures is developed. Then, using the finite element (FE) method with embedded fibers, the effective properties are computed for each of the random microstructures. This approach requires only a regular grid for the FE mesh, circumventing the requisite computationally costly and human labor intensive mesh refinement of ordinary FE in order to capture the local morphology of the composite material. Finally, a Monte Carlo simulation approach is used to obtain statistics of the computed effective physical properties. The numerical results are found in good agreement with experimental data reported in the open literature.