Thermal conductivity of shape memory polymer nanocomposites containing carbon nanotubes: A micromechanical approach

Abstract

A new micromechanical formulation based on a unit cell model is developed to predict the effective thermal conductivities of carbon nanotube (CNT)-shape memory polymer (SMP) nanocomposites. Model predictions considering interfacial thermal resistance between the CNT and SMP, agglomerated state of CNTs into the SMP matrix and CNT non-straight shape are in reasonable agreement with the experiment reported in the literature. It is found that the CNT agglomeration must be removed to obtain a maximum level of thermal conductivities of SMP nanocomposites. The effects of volume fraction, diameter, cross-section shape, arrangement type and waviness factors of CNTs as well as interfacial thermal resistance on the axial and transverse thermal conductivities of aligned CNT-reinforced SMP nanocomposites are extensively investigated. The results show that the alignment of CNTs into the SMP nanocomposites along the thermal loading can be an efficient way to dissipate the heat. When the CNT waviness increases, a nonlinear decrease in the axial thermal conductivity is occurred, however, the nanocomposite thermal conductivity along the transverse direction quickly rises. It is observed that the interfacial thermal resistance, cross-section shape and arrangement type of CNTs do not affect the axial thermal conductivity of CNT-SMP nanocomposites. But, the interfacial thermal resistance can play a key role in the transverse nanocomposite thermal conductivity. The present fundamental study is very important for understanding the thermal conducting behavior of CNT-SMP nanocomposites which may have a wide range of applications in temperature sensing elements and biological micro-electro-mechanical systems.