Phase-based FBG detectors for self-diagnosis of marine vehicles structures

In the context of a new project named SEALAB, aimed at conceiving an innovative high speed marine vehicle, a new system for monitoring the structural response and potential damages in the ship structures is under development. This system permits the real-time self-monitoring of the structure using a new system of sensor based on optical fibers equipped with FBG (fiber-Bragg-gratings) sensors. These fibers are applied using different technologies. For traditional materials, like aluminum made structures, the fibers are simply glued along the system. For composite materials, the fibers are embedded directly into the matrix. A novel HHT-based method (Hilbert-Huang transform) for damage detection of panel structures under impulsive or travelling load is proposed. The technique is able to identify the presence and the location of the damage along the panels. The measured data are processed by the HHT technique, and none a priori information is needed about the response of the undamaged structure. Damage location is revealed by direct inspection of the first instantaneous frequency, which presents a sharp crest in correspondence of the damaged section.