Structural Health Monitoring Using Fibre Optic Acoustic Emission Sensors

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.

Structural Health and Condition Monitoring with Acoustic Emission and Guided Ultrasonic Waves: What about Long-Term Durability of Sensors, Sensor Coupling and Measurement Chain?

“…These consist of thin film piezoelectric components and may offer advantages in terms of small size and power efficiency, which are both important for the integration of such devices. A second class of AE and GUW sensors uses optical fibers, either made of glass [54] or polymers [55][56][57], typically with Fiber Bragg Gratings (FBG) for sensing [58,59]. Recently, there were further materials developments for improving fiber optics performance [60].…”

“…[62] and "An important advantage of FOS [Fiber Optical Sensor] over conventional piezoelectric sensors is their high temperature resistance. Temperature resistant FBGs for AE sensing have been of interest to the industry for a variety of applications" [59]. Fiber optics sensors, different from PZT-tranducers or other piezo-transducers, are not sensitive to electromagnetic interference, and this is useful for applications in environments with strong or oscillating electromagnetic fields.…”

Optical Fiber Sensors for Ultrasonic Structural Health Monitoring: A Review

“…In this sensor (Figure 3), two tapered optical fibers are fused together using a high temperature flame [32]. This process brings the core region of the two optical fibers in contact, which in turn allows the light transfer across the tapered region [33]. For the input energy P 0 , the output energy in the two output ports is given by Equation (2) [34].…”

“…Several passive systems for their detection have been proposed, making use of FBG sensors. Some of the key publications have been reviewed by Willberry et al [33]. More recently, Jinachandran et al [151] performed a variety of experiments for AE-based detection in weld structures.…”

Pultruded FRP Beams with Embedded Fibre Bragg Grating Optical Sensors for Strain Measurement and Failure Detection

“…Some of the literature includes thermo-mechanical studies that focus on the main mechanisms which drive the evolution of the residual stresses, strains, and deformations based on the incorporation of fibre optical sensors (FOS) into composite beams [19,20]. Pressure is another parameter that has been studied by embedding FOS based on acoustic emission or plasmonic resonators [21,22], or even the study and experimentation of automated produced pultruded beams with FOS [23,24].…”