Enabling FO-Based HUMS Applications Through an Innovative Integration Technique: Application to a Rotor Blade Mockup

Although relevant examples of systems devoted to shape sensing, damage detection, load identification, etc., do exist, even based on fiber optic sensors, they are barely suited for installation on real aerospace applications due to important criticalities in the application of the fiber. However, all HUMS application based on fiber optics can be enabled thanks to the proposed Smart Veil: a technology consisting of a thin composite membrane incorporating fiber optics placed on a complex path. This integrated element makes the monitoring system easy to use/handle, robust and reliable in real operating scenarios, capable of guaranteeing precise measurements. The effectiveness of this technological solution is proven by means of the manufacturing of a sensorized helicopter blade mockup. Among the several techniques that can be adopted using a fiber optic, FBG (Fiber Bragg Grating) sensors have been selected, allowing a robust punctual measure in specific locations. The choice of sensors position was led by the idea to exploit a digital twin for shape reconstruction and load identification, so all the components of the relevant loads acting on a tail rotor blade during operation can be obtained: axial, beam bending, chord bending and torsion. All sensors benefit from the use of the smart veil that guarantees robust and precise measures. Particularly, the torsional sensors do, since they need to be placed on an ad hoc path. The static calibration test and a comparison with a strain gauges system permitted a validation and showed the advantages of the technological solution proposed.