In situ ice and structure thickness monitoring using integrated and flexible ultrasonictransducers

Abstract

Two types of ultrasonic sensors are presented for in situ capability development of ice detectionand structure thickness measurement. These piezoelectric film based sensors have been fabricatedby a sol–gel spray technique for aircraft environments and for temperatures ranging from−80 to100 °C. In one sensor type, piezoelectric films of thickness greater than40 µm are deposited directly onto the interior of a 1.3 mm thick aluminum (Al) alloycontrol surface (stabilizer) of an aircraft wing structure as integrated ultrasonictransducers (UTs). In the other sensor type, piezoelectric films are coated onto a50 µm thick polyimide membrane as flexible UTs. These were subsequently glued onto similarlocations at the same control surfaces. In situ monitoring of stabilizer outer skin thicknesswas performed. Ice build-up ranging from a fraction of 1 mm to less than 1.5 mm was alsodetected on a 3 mm thick Al plate. Measurements using these ultrasonic sensors agreed wellwith those obtained by a micrometer. Tradeoffs of these two approaches are presented.