Review on structural health interrogation using fiber bragg grating sensors

Abstract

Abstract. Fibre Bragg Grating sensors are optical fibre sensors that are now widely used in civil, mechanical and aerospace engineering for structural health monitoring and damage detection purposes. Typical parameters to be measured are strain and temperature, but also rotation, pressure, vibrations, the distance between stationary and moving or rotating components and concentration of chemical substances can be registered. These sensors have numerous advantages with respect to their piezoelectric counterparts, such as light weight, small dimensions, immunity to electromagnetic interference caused by nearby electronic devices. One of the most notable advantages of Fibre Bragg Grating sensors is the multiplexing capability, meaning that several tens to hundreds of sensors can be stacked together to increase the number of measurement points. This is a key advantage in structural health monitoring and damage detection in aerospace, pavement, bridge and other structures, where numerous points on the structure are subjected to high stresses. Moreover, fibre optical sensors are fully passivethey are capable of functioning without power supply. This review paper deals with highlighting the usage of Fibre Bragg Grating sensors in structural health monitoring and damage detection in various types of structures, namely, civil structures (bridges, pavements) and lightweight structures (aircraft, thin-walled composites), thus underlining a great significance of these sensors in structural safety.Keywords: optical fibre, FBG sensors, damage detection, SHM. Optical sensors overviewOptical fibres consist of two concentric silica layers, namely, the core and the cladding. The small differences in refractive index between both layers ensure the condition of total internal reflection of light inside the fibres, making the optical fibres efficient waveguides. Fibre optical sensors (FOS) comprise the core with a diameter of about 8 µm made of silica doped with germanium oxide and a cladding layer with a diameter of 125 µm made of pure silica. The smallest signal attenuation 0.2 dB/km is achieved at the wavelength of 1.550 nm [1].The essential difference between conventional and fibre optical sensors (FOS) is that FOS are passive -they are capable of fully functioning without power supply. Providing electrical power to the sensor in remote areas for road pavements, bridges or aircraft can be a very difficult task. FOS are sensitive to temperature, pressure, strain, gas concentration, vibrations, the distance between stationary and moving or rotating components, etc. and the raw FOS measurements are in a form of wavelength information, which is analysed and processedto reveal the vital information about the health state of the structure [2]. Optical sensors also provide higher accuracy compared to electronic analogues. This is due to the fact that the light wavelength is much shorter (1.3-1.5 µm) than the radio waves used in wireless systems (in GHz, wavelength measured in centimetres).The most promising type of fibre optic sensors ...

FBG‐Based Sensing for Structural Health Monitoring of Road Infrastructure

“…Numerous studies exist on application of FBG sensors in monitoring of the roads. Several studies have been devoted to a design of appropriate encapsulation of bare fibers before integration into pavements as the fibers themselves are fragile and can easily break [13][14][15]. In [16], authors, firstly, applied a simple layer of an epoxy resin curing and toughening agents and, subsequently, provided a steel casing encapsulation (E = 198 GPa) for increased safety, as laying of pavement implies the use of a heavy (about 30 tons) road rollers.…”

“…The performance of embedded FBG sensors within asphalt pavement was researched in studies [13][14][15]. Static tests of asphalt concrete specimens, with embedded FBG sensors, showed a linear relationship between wavelength shift and strain of the asphalt concrete thus satisfactory repeatability of the test [16].…”

Leak Detection in Water Pipes Using Submersible Optical Optic-Based Pressure Sensor

“…They are commonly used for monitoring localised physical quantities, such as strain, temperature, and pressure [5,6]. The descriptions of FBGs and their applications are widely reviewed and discussed by the authors of [7,8,9,10]. FBGs can also be integrated into different structures to develop novel optical fibre-based sensors.…”