Numerical modeling and experimental characterization of the AC conductivity and dielectric properties of CNT/polymer nanocomposites

In this work, we proposed a multiscale numerical model to estimate the electric conductivity and dielectric constants of the CNT/polymer nanocomposites, taking into account the tunneling effect between neighboring CNTs separated at nanoscale and the frequency-dependent dielectric properties of each components. Finite element method was employed to solve the formulations, and the CNTs were modeled by highly conductive line segments in order to avoid the mesh problems. Experiments have been carried out in carbon nanotubes/epoxy nanocomposites in order to compare to the simulation results. The numerical estimations of the electric conductivity are in good agreement with the experimental measurement by network analyzers. Moreover, the calculated dielectric permittivity agrees with the experimental data for the nanocomposites whose CNT content is beyond percolation threshold. Below percolation threshold, the proposed model also works well in the prediction of dielectric constants when the frequency is over 10(3) Hz.