Improved Electrical Characteristics of Airborne Radomes
ABSTRACT: Dielectric properties, and therefore radar transmission abilities, of radomes degrade with weathering, but the mechanisms causing degradation are not well understood. TRI proposes to use its three decade background in accelerated life testing; failure analysis; and composites to develop a thorough understanding of how radome materials degrade with age and usage. TRIs polymers group will also recommend substitute materials to reduce dielectric property degradation. TRIs Nondestructive Inspection (NDI) group will lead the effort to develop NDI processes for assessing dielectric property degradation. In Phase I, the team manufactured samples from cyanate ester resins with astroquartz reinforcement. Samples were then artificially aged to various levels by exposure to aggressive environments. The research team conducted microwave NDI of the panels to assess dielectric property degradation versus aging. Microscopy and spectroscopy indicates that degradation was primarily mechanical. Inspection results indicate that microwave NDI correlates well to dielectric changes caused by radome aging. Phase II will provide more realistic accelerated aging in more realistic samples to confirm degradation mechanisms. Microwave NDI processes will be greatly expanded, and data correlated to radar performance as well as aging and dielectric property changes. In addition, there are several materials replacement options for decreasing those degradation mechanisms. BENEFIT: The primary benefits learned from the Phase I outcome is that the degradation appears to dominated by mechanical aging and that handheld microwave instruments offer the promise to monitor the resulting decreases in dielectric performance over time. Phase II accelerated aging methods will provide more detailed information about the degradation mechanisms. Furthermore, there are several methods to reduce the damage caused by mechanical aging. There are tens of thousands radomes used for military and commercial aircraft, ground-based radar, weather radar, coast warning radar, and ship radar. All of these radomes would benefit from a better understanding of how radomes dielectric properties degrade; implementation of materials that age more gracefully; and ultimately a fielded nondestructive tool to measure dielectric properties without far field testing.
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