Fiber Bragg Grating Sensors for Mechanical and Thermal Prognostics and Diagnostics for Aerospace Applications

Nowadays, the usage of fiber optics is really common in several daily applications such as the telecommunications and sensoristic field. In the telecommunications field, the usage of fiber permits to have many advantages compared, for example, to the usage of copper cables. In fact, the fiber optics allow to transmit a large amount of data and with a high bit rate for long distance. Therefore, they allow doing this with low losses and there is no need to external power supply. In addition to these advantages, the fiber optics are immune to electromagnetic interference and thanks to high temperature resistance and corrosive environment, it is possible to use fiber optics in harsh environment. As above mentioned, fiber optics can be used in the sensoristic field and, in particular, we talk about Optical Fiber Sensors (OFS). Obviously, they have the same characteristics and advantages of fiber optics. Regarding to OFS, we talk about the Fiber Bragg Grating (FBG) and it represents the subject of this Thesis. This kind of sensor can be used in several applications of fields of engineering from Civil to Aerospace applications, for example to measure strain, temperature, pressure and vibration. These physical quantities are computed by using appropriate equations that relate these quantities and wavelength variations detected by FBG. Hence, it is possible to monitor structures with these sensors, by allowing mechanical and thermal diagnostics and prognostics. Therefore, they are used in medical applications. The aims of this work are to test FBG sensors and design and test different type of locking systems to lock the fiber optics. In particular, regarding to mechanical tests, locking systems differ from each other and the first type of system is designed to use a hard/soft rubber layer and other system is designed to glue the fiber optics by using the resin. Therefore, a locking system was designed to lock the fiber optic for thermal tests. Once the locking systems have been manufactured a test bench was assembled. The bench is constituted by several components including fiber optics and locking systems. Then, different measuring campaigns were performed to test the quality of locking systems and to test FBG sensors. This Thesis shows an overview about the Fiber optics and Fiber Bragg Grating sensors, then it shows the assembly of the test bench and the measurements done during the measuring campaigns. At the end, the optimum locking system and the most important results obtained are shown.