Transient conduction for thermal diffusivity simulation of a graphene/polymer and its full-field validation with image reconstruction

A 3D finite element model is presented to simulate the thermal transport properties of a polymer composite made of GradeM25 graphene nanoplatelets (GnP) in a low-viscosity bisphenol-A epoxy resin. This is a multi-scale approach that consists of a unit cell, a representative volume element (RVE) and a macroscopic specimen model. There is a hierarchy of structural scales, where the response at one size level is described by one (or more) parameters and passed to the next level up. At the unit cell level, the material nano-characteristics are used to calculate the local thermal response, while the material architecture is captured by the RVE. A statistical sample is studied and the average thermal response is compared to the macroscopic experimental data. Afterwards, the experimental reinforcement distribution is applied to the macro specimen model. The thermal diffusivity mapping was obtained numerically and compared to the flash method measurements following the CEN/CWA 16799 standard, through the decomposition and reconstruction of the fields with orthogonal Zernike polynomials and their comparison on a linear correlation plot. Finally, the simulation of the transient thermal response was successfully validated under both generic and full-field comparison. This research work is, therefore, proposing a validated simulation tool to estimate the thermal response of polymer nanocomposites, while being engineer-friendly to promote advanced material design that eliminates the trial and error approach.