Composite Structural Panel Natural Frequencies Estimation by Fiber Bragg Grating Sensors Network

The identification of the dynamic properties of composite structures is a key aspect for both structural validation and structural health monitoring in aerospace applications. In this work, the capability of Fiber Bragg Grating (FBG) sensors to identify the natural frequencies of a composite plate is experimentally investigated. An optical sensing network composed of multiplexed FBG sensors was externally bonded to the surface of the plate using a simple industrial Kapton adhesive, enabling a plug-and-play sensing configuration. Impact hammer tests were performed in order to excite the structure, and the resulting dynamic strain signals measured by the FBG sensors were processed through frequency-domain analysis to extract the modal frequencies. The obtained results were compared with those measured using a traditional accelerometer-based system adopted as reference instrumentation. The experimental results show an excellent agreement between the two measurement approaches, with discrepancies below approximately 2% for frequencies up to $300 H z$. The results confirm the potential of FBG-based sensing systems for dynamic monitoring of composite structures and open the possibility of developing smart composite panels capable of real-time vibration monitoring for advanced structural health monitoring applications.