Determination of thermo-chemical parameters affecting the oxidation recession of carbonized CFRP surface

The outer wall of reentry vehicles is covered with heat shield materials in order to protect them from severe aerodynamic heating. An ablator is a type of heat shield material effective for reentry vehicles. In particularly an ablator made of Phenolic carbon fiber-reinforced plastics (CFRP) is known to possess superior resistance against severe aerodynamic heating. Phenolic CFRP is pyrolyzed and carbonized by aerodynamic heating and is recessed by oxidation. Like graphite, carbonized Phenolic CFRP manifests distinctly different oxidation characteristics in the rate and the diffusion-controlled regions. Its surface recession in both the regions can be expressed by Metzger's equation. However, the recession behavior predicted by Metzger's equation is inaccurate, because the thermal properties of graphite are used as inputting the equation, regardless of the difference in the thermal characteristics of graphite and carbonized Phenolic CFRP. Accurate prediction of the recession of carbonized Phenolic CFRP requires a precise estimation of its activation energy E, collision-frequency coefficient ko and diffusion-controlled mass transfer constant Co. These parameters were precisely determined in this study, and it was shown that substitution these parameters enabled the accurate prediction of the recession behavior of carbonized Phenolic CFRP.