Embedded Sensors for Monitoring Fatigue Damage in Harsh Environments

This proposed program will establish the feasibility of monitoring fatigue damage in harsh, specifically wet (fuel), environments with embedded MWM-Array (eddy current sensors).  The goal is to reduce maintenance costs by enabling more frequent inspection for cracks in multi-layer structures without disassembly.  Over the past decade, the MWM-Array fatigue sensor has been developed and proven in numerous coupon, component and full-scale tests, with first flight tests scheduled for later this year.  Many applications, however, require operation in harsh environments.  This proposal addresses survivability in such demanding military aircraft applications.  This will require development of (i) lower power procedures (with enhanced electronics and cable design)s to enable operation in fuel, (ii) protective measures to ensure survival of sensors and cables (to realize savings, sensors must survive for ten to thirty years), and (iii) means for ensuring safety and survivability when sensors are mounted at faying surfaces between metal layers and under fasteners.  Furthermore, this SBIR will apply next generation MWM-Array instrumentation and signal processing for improved detection of small, buried flaws.  We will also investigate the feasibility of embedding sensors in smart bolt configurations where practical. BENEFIT: If we are successful, the Air Force will have a valuable new tool for monitoring fatigue damage in difficult to access locations, in harsh environments and without the need to disassemble the aircraft to perform the inspection.  This will reduce maintenance costs, avoid collateral damage from disassembly to gain access for inspection,  and improve fleet readiness.  This capability is directly applicable to commercial aircraft fleets and can be extended beyond aircraft to applications on ships, bridges, pipelines, power plants, and vehicles.