Thermo-mechanical properties of a piezoelectric polyimide carbon nanotube composite: Assessment of composite theories

In this work, we have characterized the thermomechanical properties of carbon nanotube based piezoelectric polymer nanocomposite using a hybrid force field for all atomistic molecular dynamic simulations. In addition, applicability of some of the well-known micromechanics composite theory in estimating carbon nanotube based polymer nanocomposite properties were assessed. We found that the primary reason for the strengthening effect of a nanocomposite with incorporation of a nanotube is the carbon-carbon bond and angle strength. The orientation of the nanotube in the polymer matrix is key to its reinforcement effect on a nanocomposite. We also observed that a perfect axial orientation does result in improving the axial modulus, but in the radial direction any strengthening for such a unidirectional composite does not seem possible without any bonding at the interface between the filler and the matrix material. The self-consistent field theory was found to be the closest with the atomistic simulation results for predicting mechanical properties of a polymer nanocomposite. The Halpin-Tsai model also demonstrated reasonable capability in predicting the strengthening effect. Mori-Tanaka model, however, underestimated the strengthening effect of carbon nanotube on the polymer matrix. It was also found that the existing composite theories are better at estimating low weight percentage nanotube strengthening effect. (C) 2014 Elsevier B.V. All rights reserved.