A new paper on the permeability of FiberForm has been published in the International Journal of Heat and Mass Transfer:

A series of experiments was performed to obtain permeability data on FiberForm®, a commercial carbon preform used for manufacturing thermal protection systems. A porous sample was placed in a quartz flow-tube heated by an isothermal furnace. The setup was instrumented to measure mass flow through and pressure drop across the sample. The intrinsic permeability and the Klinkenberg correction, which accounts for rarefied effects, were computed from the experimental data. The role of the gas temperature and pressure on the effective permeability is shown, and it is demonstrated that with proper data reduction, the intrinsic permeability is strictly a function of the micro-structure of the material. A function for the effective permeability of FiberForm, dependent on temperature, pressure, pore geometry, and type of gas is proposed. The intrinsic permeability was evaluated at K₀=5.57×10^-11 m², with a Klinkenberg parameter of 8c/d_p=2.51×10⁵ m⁻¹ and a reference porosity of ϕ^†=0.87.

Panerai, F., White, J. D., Cochell, T. J., Schroeder, O. M., Mansour, N. N., Wright, M. J., and Martin, A., “Experimental measurements of the permeability of fibrous carbon at high temperature,” International Journal of Heat and Mass Transfer, Vol. 101, October 2016, pp. 267–273.
DOI: 10.1016/j.ijheatmasstransfer.2016.05.016