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Guided waves based SHM systems: parameters selection for better 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 account certain failure mechanisms frequently inducing 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. The intent of this paper is to summarize the experiences gained by the authors in selecting the most sensitive parameters according to the type of damage to be investigated in several typology composite plate-like structures.