Anisotropic thermal conductivity measurement of carbon-fiber/epoxy composite materials

This project originated from a need for understanding heat transfer in carbon-fiber/epoxy natural-gas tanks undergoing rapid heating during refilling. This paper presents both experimental and theoretical work concerning evaluation of the thermal properties of carbon-fiber/epoxy composite materials. An effective measurement system was implemented based on steady-periodic heating: a platinum film sputtered on the surface of a sample was periodically heated by an AC current at frequency ω. The phase lag and amplitude data of a voltage signal at frequency 3ω related to the temperature response information in the platinum film were collected from the experiment. An impedance analysis model was employed to convert the phase and amplitude of the voltage to those of the temperature response. The anisotropic thermal properties were deduced from an inverse parameter estimation model, which was a least-square systematic comparison between experimental data and the theoretical model. The anisotropic theoretical solution was derived based on the Green's function solution. Poly(methyl methacrylate) (PMMA) samples were used as reference samples to verify the measurement system. Both in-plane and through-thickness thermal conductivity of carbon-fiber composite samples were obtained and presented simultaneously.