Thermal properties of composite two-layer systems with a fractal inclusion structure

TL;DR

This study investigates how the anisotropic, fractal-like inclusion structures in composite two-layer systems affect their thermal transport properties, revealing complex behaviors influenced by interface structure and orientation.

Contribution

It introduces experimental analysis of anisotropic magnetite-inclusion composites and links their thermal properties to interface complexity using lacunarity analysis.

Findings

Thermal diffusivity and conductivity measured experimentally.

Inclusion orientation significantly affects thermal behavior.

Interface complexity explains nontrivial thermal responses.

Abstract

In this work, we study the thermal transport properties of platelike composite two-layer samples made of polyester resin and magnetite inclusions. By means of photoacoustic spectroscopy and thermal relaxation, their effective thermal diffusivity and conductivity were experimentally measured. The composite layers were prepared under the action of a static magnetic field, resulting in anisotropic inclusion structures with the formation of chains of magnetite particles parallel to the faces of the layers. In one kind of bilayers, a composite layer was formed on top of a resin layer while their relative thickness was varied. These samples can be described by known models. In contrast, bilayers with the same concentration of inclusions and the same thickness on both sides, where only the angle between their inclusion structures was systematically varied, show a nontrivial behaviour of their thermal conductivity as a function of this angle. Through a lacunarity analysis, we explain the observed thermal response in terms of the complexity of the interface between the layers.