Finite element modelling and simulations on effective thermal conductivity of particulate composites

Abstract

In this paper, the finite element simulation approach for studying the steady-state heat transfer and predicting the effective thermal conductivity of composites has been proposed. 3D representative volume elements considering the polyhedral- and spherical-shaped inclusions are generated. Different meshing approaches for meshing these complex structured composites have been used, and the mesh quality is studied based on mesh metrics: element quality and skewness, and next, a convergence study is conducted to ensure mesh-independent results. Three different boundary conditions: mixed, constant temperature gradient and uniform flux has been used to predict the effective thermal conductivity of composites. The predicted results from simulations are in good agreement with the experimental values reported in the literature. It has been observed that the random orientation and interpenetration of particles lead to a much better heat flow and hence the higher values of effective thermal conductivity of composites. For high volume fraction composites, as the number of particles having interpenetration increases, their effective thermal conductivity increases. For low volume fraction composites, constant temperature gradient boundary condition overpredicts the effective thermal conductivity and for high volume fraction composites, uniform heat flux and mixed boundary conditions predict higher values. A design point study was conducted, considering the ratio of thermal conductivity of constituents, as a design parameter. It has been observed that by reinforcing the high thermal conductivity inclusions as an interpenetrating phase, the effective thermal conductivity of composites can be increased substantially. The reinforcement of very high conductivity material cannot yield the desired ETCs if the reinforced particles are rendered uniformly oriented with no contacts between them.