Investigation of Effect of High, Short Duration Temperatures on Fiber Graphitization and Resulting Property Changes in 3D Woven TPS Preforms During Entry Trajectories

To address the need for low-ballistic coefficient aeroshells with minimal impact on vehicle weight, NASA is investigating flexible thermal protection system (TPS) options. These designs typically consist of a flexible three-directional (3D) woven carbon cloth that can be stowed during flight and deployed on command to serve as a semi-rigid aeroshell during atmospheric entry. For some planned entry trajectories, the woven TPS is subjected to short duration, but extremely high heat flux levels. Since current plans call for the use of as-received non-heat treated carbon fibers in the WTPS, MR&D aims to investigate whether exposure to high temperature, short duration temperatures alters the graphitic microstructure and thus the properties of PAN-based carbon fibers.