Modal analysis and damage detection by Fiber Bragg grating sensors

Damage detection and localization are crit. issues for structural health monitoring. To this aim, many techniques have been proposed relating, the presence of damage to variations of its dynamic features between the undamaged and damaged states. Since a greater information content is localized at higher frequencies, sensing systems with adequate bandwidth and resoln. are required. Here, Fiber Bragg grating sensors with an adequate interrogation system are exploited to reveal the presence of damage on a structure. As preliminary step, modal anal. tests in a wide frequency range are performed in order to verify the performances of these optic devices to retrieve high frequency structural dynamic features. As ref. sensors, laser Doppler vibrometers and accelerometers, representative of the state of the art for this application field were exploited. Exptl. results confirm the excellent performances of Fiber Bragg gratings, not only able to detect damage but also to discriminate between different damage levels.