Abstract
Acoustic emission (AE) is widely used for condition monitoring of critical components and structures. Conventional AE techniques employ wideband or resonant piezoelectric sensors to detect elastic stress waves propagating through various types of structural materials, including composites during damage evolution. Recent developments in fibre optic acoustic emission sensors (FOAES) have enabled new ways of detecting and monitoring damage evolution using AE. An optical fibre consists of a core with a high refractive index and a surrounding cladding. The buffer layer and outer jacket both act as protective polymer layers. Glass optical fibres can be used for manufacturing AE sensors of sufficiently small size to enable their embedding into fibre-reinforced polymer composite materials. The embedding process protects the FOAES against environmental stresses prolonging operational lifetime. The immunity of FOAES to electromagnetic interference makes this type of sensor attractive for condition monitoring purposes across a wide range of challenging operational environments. This paper provides an exhaustive review of recent developments on FOAES including their fundamental operational principles and key industrial applications.
Highlights
Non-destructive evaluation (NDE) is useful for monitoring structural components and machinery in real time or during maintenance [1,2,3,4]
Optical fibre sensors have gradually become more popular for acoustic emission (AE) sensing based on various designs including fused-tapered couplers [23,24,25], Mach-Zehnder sensors [26,27], Michaelson interferometers, Fabry-Perot interferometers [28,29] and fibre Bragg gratings (FBGs) [30,31]
Other devices thatpresence have been considered as an alternative to piezoelectric technique is simple, robust, and able to characterise the frequency content of the detected damage include fibre optic ring AE sensors (FORAES) [62]
Summary
Non-destructive evaluation (NDE) is useful for monitoring structural components and machinery in real time or during maintenance [1,2,3,4]. Optical fibre sensors have gradually become more popular for AE sensing based on various designs including fused-tapered couplers [23,24,25], Mach-Zehnder sensors [26,27], Michaelson interferometers, Fabry-Perot interferometers [28,29] and fibre Bragg gratings (FBGs) [30,31]. Lamb waves can propagate over long distances throughout the thickness of the plate thanks to the lower levels of attenuation This means that AE sensors can be at a distance from the actual area where damage has occurred and still be capable of detecting and monitoring it as it evolves [37,38].
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