Probability ellipse method for damage detection in a composite winglet

It is well known that composite materials are founding increasing applications in the transport field thanks to their high strength to mass ratio. However, their use in primary structures is very challenging because of their high sensitivity to in-service damages and manufacturing defects. As a result, the current adopted damage tolerance approach leads to the oversizing of such structures. Structural health monitoring systems, aimed to the real time damage detection, can provide several benefits in terms of lightweight of the structures, maintenance operations and inspection costs. This paper deals with the use of the Probability Ellipse (PE) method, based on the propagation of ultrasonic guided waves on a composite winglet of a small aircraft. The PE method estimates the probability of the presence of the damage in the monitored area, starting from the knowledge of selected damage indexes for each sensors-path. The winglet, equipped with piezoelectric sensors, usable as both actuating and receiving devices, has been numerically and experimentally investigated under several configurations, varying the actuator location. Sensitivity analysis has been performed to assess the effectiveness of the PE method. The accuracy of the PE method in detecting both location and damaged area is herein discussed.