FBG based transducers for morphing applications

The measurement of large deformations represents a challenging issue for many engineering applications. To name a few, morphing and deployable aerospace structures, due to the intrinsic large deformations, require dedicated sensing systems able to capture the current geometry (shape reconstruction) and to detect the stress level (structural health monitoring). Conventional sensors, on one hand, due to the material structural limitations, could not assure an adequate measurement, and, on the other, may interfere with other instrumentation. The optical fiber technologies present advantages in terms of channels number and wiring needs; furthermore the specific information carrier, that is the light, prevents from any interference with other onboard systems. Finally, limitations of measurement due to the glass intrinsic fragility may be overcome integrating the sensors with a dedicated strain modulation supporting structure. The paper at hand just focuses on Fiber Brag Grating (FBG) - based sensors, conceived to modulate large strains. For each transducer, the design phase is illustrated: moving from the specifications, the design parameters are then identified and their optimal configuration is assessed. Preliminary demonstrators are manufactured and tested, allowing a comparison with the numerical outcomes. All proposed concepts exhibited a wide measurement range, a high level of versatility (due to the possibility of tuning the same sensors for different measurement conditions). The work ends with a critical discussion on the enhancements further achievable and on the activities yet necessary to increase the readiness level.