Finite Element Modeling Of Carbon Nanotube Reinforced Polymer Composites And Evaluating Its Thermal Conductivities

Abstract

High thermal conductivity of carbon nanotubes has motivated us to study and understand the thermal mechanisms in nanocomposites. Though several theoretical models predict a high thermal conductivity for CNT reinforced polymer composites, the experimental validation are not so encouraging. A finite element model of MWNT reinforced nanocomposite is developed based on continuum mechanics approach. The finite element model is a representative volume element (RVE) with single MWNT inclusion. The inclusion is modeled based on the continuum model of MWNT as effective solid fiber [22].The interface resistance between the nanotube and the matrix material is modeled using thermal contact elements. The finite element analysis was carried out keeping volume fraction of MWNT fibers as constant and varying three important parameters which influences the effective thermal conductivity. Analysis with varying volume fractions of CNT fibers was also carried out to study the influence of volume fraction. The results obtained were in agreeable range with the theoretical calculations made based on the work of Bagchi and Nomura [22]. The effective thermal conductivity of MWNT reinforced nanocomposites with MWNTs of high aspect ratios showed gradual increase in conductivity with increase in length while it showed a drastic decrease in effective thermal conductivity with increase in the diameter of the MWNT inclusion. The finite element analysis showed that the interface resistance between the nanotube and the matrix material does not affect effective thermal conductivity noticeably which is contradictory with few theoretical models which attribute interface resistance for lower than expected effective thermal conductivity. The analysis predicts linear increase of effective thermal conductivity with increase in volume fraction of the MWNT fibers in matrix material; this is also in accordance with the theoretical model. The above analysis also validates the use of finite element approach based on continuum mechanics in studying the overall behavior of the nanocomposites.