Title: A Micromechanics Model for the Electrical Conductivity of Nanotube-Polymer Nanocomposites

Gary D. Seidel a, Dimitris C. Lagoudas
Department of Aerospace Engineering
Texas A&M University
College Station, TX 77843-3141

Journal of Composite Materials -- 2009 -- Volume 43, Issue 9, pp. 917-941

Abstract
The introduction of carbon nanotubes into non-conducting polymers has been
observed to yield orders of magnitude increases in conductivity at very low concentrations
of carbon nanotubes. These low percolation concentrations have been attributed
to both the formation of conductive networks of carbon nanotubes within
the polymer and to a nanoscale effect associated with the ability of electrons to
transfer from one carbon nanotube to another known as electron hopping. In the
present work a micromechanics model is developed to assess the impact of the
effects of electron hopping and the formation of conductive networks on the electrical
conductivity of carbon nanotube-polymer nanocomposites. The micromechanics
model uses the composite cylinders model as a nanoscale representative volume
element where the effects of electron hopping are introduced in the form of a continuum
interphase layer, resulting in a distinct percolation concentration associated
with electron hopping. Changes in the aspect ratio of the nanoscale representative
volume element are used to reflect the changes in nanocomposite conductivity associated
with the formation of conductive networks due to the formation of nanotube
bundles. The model results are compared with experimental data in the literature
for both single- and multi-walled carbon nanotube nanocomposites where it is observed
that the model developed is able to qualitatively explain the relative impact
of electron hopping and nanotube bundling on the nanocomposite conductivity and
percolation concentrations.

Key words: A. Carbon Nanotube, B. Nanocomposite, C. Electrical Conductivity,
D. Micromechanics, E. Composite Cylinders