A new micromechanical method for the analysis of thermal conductivities of unidirectional fiber/CNT-reinforced polymer hybrid nanocomposites

Abstract

In this work, a physics-based hierarchical approach is established to evaluate thermal conducting behavior of carbon fiber (CF)-carbon nanotube (CNT)-reinforced polymer hybrid nanocomposites. For this purpose, the Maxwell-Garnett type effective medium (EM) method is appropriately coupled with a unit cell-based micromechanical model. The predictions of the thermal conductivities of fiber-CNT-reinforced polymer hybrid nanocomposites are verified with the available experimental data. Very good agreement is found between the model predictions and experiments. For a more realistic prediction, considering (i) the CNT random orientation, (ii) the CNT random distribution within the polymer, (iii) the CNT non-straight shape and (iv) the CNT/polymer interfacial thermal resistance is essential in the micromechanical analysis. The influences of volume fraction and aspect ratio of CF, volume fraction and dispersion type of CNTs on the hybrid nanocomposite thermal conductivities along the longitudinal and transverse directions are examined. It is found that the CNT dispersion type within the hybrid nanocomposites can significantly affect the overall heat conducting behavior of such new systems. Agglomeration of CNTs leads to a reduction in the thermal conductivity of hybrid nanocomposites along the transverse direction.