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30 December 2008 Fibre Bragg grating acoustic emissions and transmission sensor in carbon fibre composites
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Acoustic sensors are used in Structural Health Monitoring (SHM) for the detection of impacts and strain. However, secondary damage may result from the initial damage. This secondary damage, such as delamination or cracking, may not be detectable by the SHM system. This is a significant problem for passive sensing systems, such as those based on fibre optics, where signals cannot be actively generated to interrogate the structure. The integration of NDE by robotic agents into a SHM sensor network enables the detection and monitoring of a wider variety of damage. Communicating via acoustic transmissions represents a wireless communication method for robotic agents to communicate to the SHM system without the addition of extra hardware, as piezoelectric transducers are commonly used in NDE. The effect of Carbon Fibre Composites (CFC) on the ability to use acoustic transmission needs to be determined. We present results for the detection of Acoustic Emissions and Transmissions (AET) in a CFC laminate. The optical fibre AET detector was a Fibre Bragg Grating (FBG). Two FBG AET sensors were compared, one coupled to the surface of the carbon fibre sheet, and one embedded within the lay-up. Results compare the transfer function, frequency response, and transient response of the sensors. The embedded FBG receiver was also used to detect an actively generated acoustic transmission. A piezoelectric receiver was also used for comparison. The embedded FBG was found to give significantly better performance in all of the parameters considered for the surface coupled FBG.
© (2008) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Graham Wild and Steven Hinckley "Fibre Bragg grating acoustic emissions and transmission sensor in carbon fibre composites", Proc. SPIE 7268, Smart Structures, Devices, and Systems IV, 726814 (30 December 2008);

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