Elliptical triangulation method for damage identification on a complex aeronautical structure

Composite structures are very appealing in aeronautic applications due to their unique stiffness to mass ratio but, due to high sensitivity to damages and defects, their use is still limited to oversized structure. For this reason, in the last years, interest in Structural Health Monitoring (SHM) has increased exponentially. The process of monitoring in real-time a structure, referred to structural health monitoring, consists of several steps: damage detection, localization, classification, and quantification. Few non-destructive guided waves-based techniques have been developed. The damage detection method used in this paper is the elliptical triangulation one, which is based on the propagation of ultrasonic waves in each sensing paths. The test article under investigation is a winglet made of fabric laminate of fiberglass infused in epoxy resin and foam coring. In view to detect damages, the winglet has been equipped with piezoelectric sensors, which act both as sensors and as actuators. A database at the unknown (and possibly damaged) state is compared to a healthy reference database. The elliptical triangulation method has been applied to the recorded signals and results, in terms of damage positioning and detection of the damaged area, have been assessed. Additional information about the damage paths have been verified by using the damage indexes.