Applications of Fiber Bragg Grating Sensors in the Composite Industry

Abstract

Optical-fiber sensors based on fiber Bragg gratings (FBGs) provide accurate, nonintrusive, and reliable remote measurements of temperature, strain, and pressure, and they are immune to electromagnetic interference. FBGs are extensively used in telecommunications, and their manufacture is now cost-effective. As sensors, FBGs find many industrial applications in composite structures used in the civil engineering, aeronautics, train transportation, space, and naval sectors. Tiny FBG sensors embedded in a composite material can provide in situ information about polymer curing (strain, temperature, refractive index) in an elegant and nonintrusive way. Great improvements in composite manufacturing processes such as resin transfer molding (RTM) and resin film infusion (RFI) have been obtained through the use of these sensors. They can also be used in monitoring the “health” of a composite structure and in impact detection to evaluate, for example, the airworthiness of aircraft. Finally, FBGs may be used in instrumentation as composite extensometers or strain rosettes, primarily in civil engineering applications.

Monitoring LCM Process by FBG Sensor Under Birefringence

“…Optical fibre sensors constitute an attractive solution for composite process monitoring since quite a long time [10][11][12], particular attention to RTM applications has been paid [13][14][15][16]. Because of their low intrusivity, they can be easily embedded into the fibrous preform or the laminas [17][18][19].…”

“…Finally, considering that no shear is induced by the thermo-mechanical loading in the (y, z) plane, the fibre optical frame of reference (1,2,3) Now, direct problem can be expressed injecting Equations (10) and (11) in Equation (9), considering that the strain at infinity is the sum of a mechanical and a thermal contribution. a c ð Þ being the in-plane CTE vector of the composite,…”

Monitoring Manufacturing of Composites Using Embedded Distributed Optical Fibre Sensors

“…Fibre reinforced polymers (FRP) are a well-known example of engineering materials, which its high strength and low density properties, primarily, make them clearly attractive for use in transport, infrastructure, energy and aerospace industries [1]. For such purposes several manufacturing techniques and processes had been developed [2] in order to extend shape's limits, improve the final product's quality, increase volume production and lower costs as well.…”

“…Strain gages, amongst other sensors, had been largely employed to monitor the curing stages in the fabrication of FRP components and, in the last 20 years, optical fibre sensors (OFSs) had been incorporated to provide a non-invasive in situ channel to track in real time the composites' behaviour while being manufactured and even after at operational conditions [1,2,[4][5][6][7][8][9]. Despite the employment of either strain gages or OFSs (fibre Bragg grating or extrinsic Fabry-Pérot interferometric sensors) for cure monitoring [10], the information obtained from these sensors is only punctual and cannot cover a larger sensing region.…”

Viability of using an embedded FBG sensor in a composite structure for dynamic strain measurement

“…Therefore, development of smart composite structures that comprises of integrated sensors, actuators and micro-processor(s) becomes a great challenge in this century. Fibre-optic Bragg grating (FBG) strain and temperature sensors have been broadly accepted as intrinsic structural health monitoring devices for measuring strains (mechanical and thermal), corrosion and vibration characteristics of smart composite structures [1][2][3]. The advantages of using the FBG sensors as embedded sensing devices of the composite structures include their small physical size, immunity of electromagnetic interference, lightweight, relative signal stability and suitability for wavelength multiplexing.…”