MULTI-PARAMETERS SELECTION AND STATISTICAL PATHS ANALYSIS IMPLEMENTATION IN A GUIDED WAVES BASED SHM SYSTEMS FOR RELIABLE IDENTIFICATION AND LOCALISATION OF DAMAGES IN COMPOSITES STIFFENED PLATES

Structural Health Monitoring deals mainly with structures instrumented by secondary bonded or embedded sensors that, acting as both signal generators and receivers, are able to “interrogate” the structure about its “health status”. This innovative approach to the damage analysis is particularly promising for reducing the maintenance costs and eventually the weight of aerospace composite structures, without any reduction of the safety level required. These structures are currently designed and employed with significant reduction of the pristine material allowables to take in account of certain failure mechanisms that frequently bring to relatively small hidden damages called Barely Visible Damages, consisting among others in delaminations and/or debondings and being detectable only by specific instruments operated by trained personnel. It has been proved that the propagation of guided waves is affected by the presence of such type of damages, but their effective identification and localization depends on the accurate “tuning” of the wave characteristic (frequency, amplitude, velocity, mode) as well as on the proper selection of the best parameter of the specific wave mode selected and data analysis algorithm. This paper presents a review of the methodologies implemented and technologies tested by the authors within the latest years within two European funded research project as well as an overview of next futures research activities aimed at the implementation of guided waves based SHM system on a real aircraft.