Embedded Fiber Optic Sensors for High Strain Composite Components
Helicopter rotor systems are increasingly using flexible composite structures to provide the required control movement for the rotor blades. These structures such as rotor head flex beams can experience very high surface strains, which can be in the order of 15,000 με. This makes it difficult for them to be monitored using conventional surface bonded strain sensors. Helicopter rotor hubs incorporating thick composite flexures are subjected to delamination failures with correlate to bending excursions. Measurement of this deflection could be used to predict remaining useful life of the flexure and other hub components. Previous efforts to measure surface strains using fiber optic sensors led to mixed results and prompted an effort to explore embedded sensors. As part of a Vertical Lift Consortium project, the authors tested proof of concept manufacturing specimens to establish the ability of the sensors to survive the cure process in a closed cavity mold tool.