The Air Force Research Laboratory Materials and Manufacturing Directorate (AFRL/RX), working with Northrop Grumman and Universal Technology Corporation, has developed a portable, nondestructive evaluation (NDE) hand-held measurement and maintenance sensor system to characterize materials beneath aircraft topcoats.
The new system was conceived under the Next Generation Sensor (NGS) program and was designed to interrogate and measure electrical properties of specialty materials under thick ceramic tiles, stated Juan G. Calzada of the Directorate's Metals, Ceramics, and NDE Division.
"We produced and delivered a first-of-its-kind, hand-held NDE capability to measure specialty material electrical performance through topcoats and under thick protective ceramic tiles. This advanced technology provides the Air Force with a new, effective capability to nondestructively assess the performance and quickly quantify the degradation of materials underneath the outer layers of military aircraft," Calzada said.
"The program effectively demonstrated the capabilities of the advanced new sensor technology in a laboratory setting and culminated in the successful fabrication of two prototypes for testing and evaluation on operational aircraft," he added.
"Air vehicles incorporate specialty materials in advanced military aircraft structural designs. These materials must operate under very harsh conditions such as high temperatures and extreme vibroacoustic loads, both of which can lead to material degradation despite protection by a thick ceramic thermal barrier. Identifying and ascertaining the level of material degradation, therefore, is critical in maintaining the integrity and performance of the air vehicle's specialty materials," Calzada explained.
"Far-field images can identify a general problem but they cannot isolate specific points of degradation that may be due to the specialty material. Hence, once the general area has been identified, a large area of outer tiles must be removed in order to expose the specialty material for direct contact measurements. This is a costly process, both in labor hours and material replacement costs. The hand-held NGS tool measures the specialty material directly, without requiring tile removal, and thereby reduces the cost of repairs and inadvertent damage to other surrounding coatings and structures," he said.
The primary goal of the NGS program was to research and develop a through-tile measurement capability using a hand-held NDE tool to measure the specialty material under thick thermal protective coatings, Calzada emphasized. The program had three main tasks: research and develop a system design concept to meet program requirements; develop and fabricate reference coupons and standards; and develop a prototype hardware and software system and evaluate its performance in a laboratory and on-aircraft environment.
"Under the first task, the research and development team investigated the frequency requirement to achieve optimal detection capability. The team then selected the best candidate solution based on a trade study of four different antenna configurations, designed and packaged an enclosure with custom electronics to minimize external hardware and wiring, and modified the NGS software to achieve program goals," he said.
"In the second task, the team selected representative materials and assembled them to establish baseline reference standards. The reference standards were used to calibrate the NGS system response. The third and final task addressed different target locations caused by the tapered tiles of varying thicknesses. Sensor response as a function of the target-to-sensor distance (or the down-range distance) was also investigated. The team then formulated a down-range correction scheme in conjunction with the reference standards," Calzada said.
"At the conclusion of the effort, the team designed and successfully fabricated and delivered two NGS prototypes for testing and evaluation on operational aircraft. Through combined effort, the program effectively demonstrated the new system's capabilities and successfully met all program requirements. Transition of the new sensor technology supports the warfighter through improved maintenance practices and enhanced mission readiness," he added.
Pete Meltzer jr
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