Micromechanical estimation of effective thermal conductivities of metal matrix nanocomposites with local carbon nanotube agglomeration

This study aims to estimate effective thermal conductivities of metal matrix nanocomposites (MMNCs) containing carbon nanotubes (CNTs) using a new hierarchical micromechanical method. Nano-filler agglomeration made of CNTs into the MMNCs, frequently encountered in real engineering situations, is considered as the main novelty of this approach. Also, two important parameters, including CNT curvature and interfacial thermal resistance between the CNT and metal matrix are taken into account in the micromechanical modeling. The developed hierarchical approach is validated through the comparison with the experimental measurements available in the literature. When CNTs are not well dispersed into the metal matrix, by incorporating the interfacial thermal resistance, CNT curvature and agglomeration, the predictions are in good agreement with the experiment of MMNC thermal conductivities. The results reveal that the CNT agglomeration can dramatically decrease the MMNC thermal properties. It is confirmed that the key issues to enhance the thermal conductivity of CNT-reinforced MMNCs are homogeneous distribution of CNTs and decrease of CNT/metal interfacial thermal resistance. Also, it is observed that the MMNCs show a significant improvement of thermal conductivity by alignment of CNTs into the metal matrix. The effects of CNT volume fraction, diameter and length on the MMNC thermal conductivities are examined. (C) 2019 Elsevier B.V. All rights reserved.