Development and Integration of a Fiber-Optical Sensor System for Rotor Blade State Observation

Health and Usage Monitoring Systems (HUMS) for helicopter rotor blades arise the demand for non invasive surveillance methods for slender composite structures. Integrating optical sensor systems within the manufacturing process of rotor blades holds challenges in fiber bonding, handling, the layup process and curing. Examining the steps of fiber integration using a co-bonding approach, the present work enlightens the challenges faced while manufacturing instrumented rotor blades. Apart from sensor integration it is crucial to show feasibility of integrated optical sensing networks. Measuring strain from Fiber Bragg Gratings (FBG), a deformation algorithm is applied to determine blade deflection along the airfoil section of a rotor blade using a NACA 0012 profile. Results from static deformation tests are used to validate the algorithm. In conclusion an experimental modal analysis is conducted and results obtained by accelerometers are compared to the ones from finite element simulation and to the eigenfrequencies measured by the FBG system.