Flexible CMUT as smart tool for nondestructive testing of aircraft composite structures

In avionics, safety is a crucial aspect and nondestructive testing (NDT) is a mandatory inspecting procedure to ensure the quality of materials before and during the lifetime of the aircraft, evaluating both the status of the materials and the degradation of the different parts of an aircraft. Especially in recent composites like Carbon Fibre Reinforce Plastics the presence of defects or the disbonds caused from accidental impacts can be very dangerous for the integrity of the wings, fuselage, etc. Among the different methods implemented in non-destructive testing, ultrasonic testing is the most common sub-surface technique to detect defects in welds, fittings, joints, bolts and adhesive bond quality. Capacitive Micromachined Ultrasonic Transducers (CMUTs) can be utilized to this end, thus permitting portable and potentially low-cost inspection. In this work, we present the fabrication and characterization of flexible CMUTs, and we discuss their potential use in NDT probes to be embedded directly on the aircraft to allow continuous and real-time monitoring of the different parts of an aircraft.