Study of FBG-based optical sensors for thermal measurements in aerospace applications

Abstract

Optical fibers have revolutionized several technological sectors in recent decades, above all that of communication, and have also found many applications in the medical, lighting engineering, and infrastructural fields. In the aerospace field, many studies investigated the adoption of fiber optics considering the planned transition from fly-by-wire to fly-by-light flight controls. A significant feature of optical fiber is its ability to be used not only as a transmission medium but also as a basis for fiber-embedded sensors; one of the most prominent types is based on Bragg gratings (FBGs). FBGs can replace several traditional sensors, providing measures of temperature, vibrations, and mechanical deformation. Optical sensors provide many advantages over traditional, electrical-based sensors, including EMI insensitivity, ease of multiplexing on a single line, resilience to harsh environments, very compact sizes and global weight saving. Furthermore, punctual knowledge of the temperature field is essential to perform the thermal compensation of the optical sensors used for strain measurements. In this work, the authors analyzed the performance of thermal sensors based on FBGs to verify their stability, accuracy, and sensitivity to operating conditions. Two different methods of FBGs surface application have been considered (gluing with pre-tensioning vs. non-tensioned bonding). The results were then compared to those acquired using typical temperature sensors to determine the relationship between the observed temperature and the Bragg wavelength variation (i.e. the proportionality coefficient Kt). The effects on the proportionality coefficient Kt, arising from fiber pre-tensioning and thermal expansion of the structural support, were then evaluated by comparing the results obtained with the two bonding approaches.

Fiber Bragg Grating Sensor Networks enhances the in-situ real time monitoring capabilities of MLI Thermal Blankets for Space Applications

“…Scheme of optical fiber working principle [24] The maximum allowed angle for the light to enter in the fiber is calculated as:…”

Analysis of the fixing process of FBG optical sensors for thermomechanical monitoring of aerospace applications

“…The aged sample is exclusively subjected to changes in temperature, while the newest is subjected to both changes in temperature and strain due to settlement. Considering the linear correlation between Δλ and Δε and ΔT [1][2][3], the Δλ T in the newest sample is equivalent to the λ in the aged sample, the latter can be subtracted from the λ in the newest sample. Thus we are left with λ ε of the newest sample:…”

Influence of processing parameters on the resin pocket geometry of smart composites embedded with Fiber Bragg Grating sensor and its fast prediction

“…Fiber Bragg Grating (FBG) sensors, known for their small size and weight, immunity to electromagnetic interference, and resistance to corrosion, 2,3 are one of the preferred sensors used in smart composites. [4][5][6][7][8][9][10] Figure 1 presents one instance of the potential application of smart composites embedded with FBG sensors used in the intelligent wing skin, which enables online monitoring of deformation and damage. 11 In addition, FBG sensors are also increasingly applied in the space domain.…”

“…[4][5][6][7][8][9][10] Figure 1 presents one instance of the potential application of smart composites embedded with FBG sensors used in the intelligent wing skin, which enables online monitoring of deformation and damage. 11 In addition, FBG sensors are also increasingly applied in the space domain. Aimasso et al have constructed FBG networks to monitor the temperature distribution of Multi-Layer Insulation (MLI) blankets, which can aid in optimizing the thermal regulation of the spacecraft.…”

“…With the application of these smart composites, real‐time monitoring of the health state of aircraft can be achieved, leading to its enhanced safety and reliability. Fiber Bragg Grating (FBG) sensors, known for their small size and weight, immunity to electromagnetic interference, and resistance to corrosion, 2,3 are one of the preferred sensors used in smart composites 4–10 . Figure 1 presents one instance of the potential application of smart composites embedded with FBG sensors used in the intelligent wing skin, which enables online monitoring of deformation and damage 11 …”