Thermomechanical analysis of foulants and graphene platelets reinforced polymer matrix coated steel substrates

Abstract

Graphene-polymer nanocomposite coatings are used to improve upon the thermal conductivity of metallic substrates. Here we quantify the enhancement provided by coatings comprised of graphene nano platelets (GNPs) of aspect ratios 1, 1.25, 1.5, 1.75, and 2 and mass fractions 0.1, 0.3, and 0.5 either randomly distributed or aligned in one-direction in an epoxy matrix. We first find thermal conductivities, thermal expansion coefficient and the elastic moduli of the homogenized GNPs/matrix by using results of the 3-dimensional (3-D) deformations of the GNPs/matrix representative volumes analysed by the finite element method (FEM). These values are compared with those determined from the rule of mixtures, the inverse rule of mixtures, and the Halpin-Tsai equations. They are then used to analyse, by the FEM, 2-D uncoupled thermo-mechanical deformations of a stainless-steel plate coated with either a foulant (biofilm, aluminium oxide, magnesium carbonate, and calcium sulphate) or a thin GNPs/epoxy layer. It is found that the biofilm hinders most the heat exchange between the plate and its surroundings and the unidirectional oriented GNPs/epoxy coating the least. For the system studied, the compressive normal stress induced at the perfectly bonded interface between the coating and the steel plate can hinder delamination there.