NDE FOR CHARACTERIZING OXIDATION DAMAGE IN REINFORCED CARBON-CARBON USED ON THE NASA SPACE SHUTTLE THERMAL PROTECTION SYSTEM

摘要

In this study, a coated reinforced carbon-carbon (RCC) sample of the same structure and composition as that from the NASA space shuttle orbiter's thermal protection system was fabricated to have predictable oxidation damage. The sample was fabricated by drilling holes to the bottom of the coating and oxidizing the sample to create cavities in the carbon substrate underneath the coating as oxygen reacted with the carbon and resulted in its consumption. The cavities varied in diameter from approximately 1.4 to 3 mm (as measured optically). The sample was used as a standard to determine capabilities of state-of-the-art nondestructive evaluation (NDE) methods for detecting and sizing oxidation damage beneath a mostly intact coating in RCC. Both one and two-sided NDE methods are used. One-sided methods are practical for on-wing inspection, while two-sided methods might be applicable in situations where RCC panel removal is possible. Comparisons of diameter and depth obtained from NDE measurements with those from optically-measured void sizes are shown.