Radial thermal conductivity of a PAN type carbon fiber using the 3 omega method

Rodrigo Andres Olaya Gomez (1) , Bertrand Garnier (1)

1 LTeN - Laboratoire de Thermique et d’Energie de Nantes

The prediction of the effective thermal conductivity of composites filled with carbon fibers requires the knowledge of the microstructure and composition of the composite, the orientation of nonisometric filler, the thermal conductivities of both phases and the thermal contact resistances between fibers and also between fibers and matrix. Due to the anisotropy of carbon fibers, one should know both their axial and radial thermal conductivities. Contrary to the axial thermal conductivity of carbon fiber, there are not much work on the radial one. The present work describes the characterization of the thermal conductivity of carbon fiber in the radial direction using the 3 omega method with a constant current source. One key point is the use of de-ionized water around the carbon fibers to enhance radial heat transfer. An appropriate thermal model is required in order to estimate the radial thermal conductivity. Therefore, analytical 1D and 2D thermal models are developed using quadrupole methods to describe heat transfer in the carbon fiber using periodic regime and are compared with a 2D numerical model. It appeared that the use of a 1D heat transfer model induces some bias until 50.3 % on the estimation of the radial thermal conductivity showing that residual axial heat transfer still occurs. Therefore the 2D thermal model is more appropriate and is used with the experimental data to estimate the radial thermal conductivity. In addition, a detailed sensitivity analysis of the unknown parameter is performed that allows to find the best range of operating conditions especially the frequency range and the effect of the type of surrounding material. Measurements are performed with PAN type carbon fiber (FT300B) of 6 to 8 micrometers diameter and various lengths from 0.5 to 2.5 mm embedded in de-ionized water. Finally, radial thermal conductivity values are shown to be about 10 times smaller than the axial one, revealing strong anisotropy of the studied carbon fiber.

Mots clés: radial thermal conductivity; carbon fiber; 3omega method; quadrupole method

Domaines: Sciences de l'ingénieur [physics]

Rodrigo Andres Olaya Gomez, Bertrand Garnier. Radial thermal conductivity of a PAN type carbon fiber using the 3 omega method. International Journal of Thermal Sciences, 2022, 172, pp.107321. ⟨10.1016/j.ijthermalsci.2021.107321⟩. ⟨hal-03430963⟩