<i>In situ</i>ice and structure thickness monitoring using integrated and flexible ultrasonic transducers

Abstract

Two types of ultrasonic sensors are presented for in situ capability development of ice detection and structure thickness measurement.These piezoelectric film based sensors have been fabricated by a sol-gel spray technique for aircraft environments and for temperatures ranging from -80 to 100 • C. In one sensor type, piezoelectric films of thickness greater than 40 μm are deposited directly onto the interior of a 1.3 mm thick aluminum (Al) alloy control surface (stabilizer) of an aircraft wing structure as integrated ultrasonic transducers (UTs).In the other sensor type, piezoelectric films are coated onto a 50 μm thick polyimide membrane as flexible UTs.These were subsequently glued onto similar locations at the same control surfaces.In situ monitoring of stabilizer outer skin thickness was performed.Ice build-up ranging from a fraction of 1 mm to less than 1.5 mm was also detected on a 3 mm thick Al plate.Measurements using these ultrasonic sensors agreed well with those obtained by a micrometer.Tradeoffs of these two approaches are presented.