Description: This program addresses the need for non-destructive evaluation (NDE) methods for quality assessment and defect evaluation of thermal protection systems (TPS), including permanently installed sensors for TPS condition, stress and temperature monitoring. Novel linear drive eddy current methods are proposed for NDE of carbon-based TPS materials, such as three dimensional woven fiber composites and felts. Using a combination of physics-based models, multivariate inverse methods, high resolution imaging, and innovative sensor array constructs the developed methods will independently monitor the material characteristics of interest. In Phase I, the focus is on enhancing and adapting methods developed for carbon-based composite structures and laminates and demonstrating feasibility of these enhanced methods for three-dimensional woven composites and felts. JENTEK's physics-based methods for diagnostics of layered media using MWM-Array technologies, including an eddy current micromechanical model extension for composites, have been demonstrated for condition stress and temperature monitoring. MWM-Arrays have a linear drive that permits both scanning type imaging and permanent installation for monitoring of anisotropic properties, temperature, and stresses at multiple depths. The projected depth of the magnetic field into the test material can be adjusted through the sensor dimensions and excitation frequencies; this enables inspection of materials more than 1.0-in. thick and supports measuring far-side surface recession in ablator materials. JENTEK delivered the MWM-Array solution used by NASA KSC on the Space Shuttle Leading Edge to detect damage of the Reinforced Carbon-Carbon (RCC) thermal protection tiles; thus JENTEK is well-positioned to deliver a practical TPS NDE solution.

Benefits: If the program is successful, it will demonstrate the capability of the MWM-Array technology to measure relevant material properties and structural damage in the advanced materials in spacecraft thermal protection systems. This type of analysis tool for detection of damage may be useful for the Multi-Purpose Crew Vehicle, composite overwrapped pressure vessels (COPV's), exhaust nozzles, and other critical composite structures. NASA customers that may benefit from these analysis tools include the Commercial Orbital Transportation Services (COTS) spacecraft manufacturers and other interplanetary programs such as science exploration mission vehicles and human crew vehicles.

There are numerous applications in which NDE measurement and analysis tools are needed to verify design requirements of advanced composites, such as three-dimensional woven materials. These include applications for commercial aircraft, wind turbines, land vehicles and composite repairs for pipelines and structures. Examples are inspection of commercial jet engine blades and fuselage components, wind turbine blades, land vehicle frames and liquid natural gas fuel pressure vessels and other structures where proper woven fiber orientation and defect free structures are critical for strength and fatigue life. It is expected that this technology could also be transitioned to support military aircraft fleets which contain substantially composite structures.