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182 Luis Rabelo, Edgar Gutierrez, Sayli Bhide et al.

(SiC) coating (Gordon, 1998). The manufacturing process, the temperature profiles, and
the infusion rates can create cavities in the carbon-carbon substrate. Micro-cracks in the
SiC coating can be also created. These substrate cavities and coating micro-cracks result
in a material with complex behavior (a tough-brittle material behavior with plasticity -
Figure 10). This needs to be emphasized due to the extreme environment and conditions
to be experienced during the re-entry phase of the orbiter.

Figure 9: The left wing of the NASA Space Shuttle with Reinforced Carbon-Carbon Panels (NASA,
2006). The only panels numbered in the picture are those panels numbered 1 through 10, 16 and 17.
There are 22 RCC panels on each wing's leading edge.

The manufacturing lead time of RCC panels is almost 8 months and their cost is high
due to the sophistication of the labor and the manufacturing equipment. It is an
engineered to order process. It will be good to know the health and useful life of an RCC
Panel. The predictive system can provide a future outcome of over-haul or disposal.
NASA developed several Non-Destructive Evaluation (NDE) methods to measure the
health of the RCC materials such as advanced digital radiography,, thermography, high
resolution computed digital tomography, advanced eddy current systems, and advanced
ultrasound (Madaras et al., 2005; Lyle & Fasanellaa, 2009). From those, thermography is
the favorite one due to its features such as easy to implement in the orbiter’s servicing
environment in the Orbiter Processing Facility (OPF), non-contacting, one-sided
application, and it measures the health of the RCC panel (Cramer et al., 2006). This NDE
method can be performed during flights. In addition, this information can be fed to a