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Title: Fibre optic sensors for monitoring the structural health of aerospace vehicles
Author: Richards, W. L.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2006
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The primary aim of this thesis is to fill important voids in the knowledge base regarding the accuracy and performance of fibre optic sensors adhered to the surface and embedded within advanced composite materials. Secondarily, the performance of the structure with embedded fibre optic sensors is also considered, with particular interest in the degradation of host strength and durability due to the embedment of optical fibre sensors. Towards this aim, a comprehensive investigation was conducted, ranging from small-scale materials to large-scale aerospace structures. Several types of fibre optic sensors were attached to structural surfaces and embedded in composites for a variety of configurations with respect to the structural fibre direction of adjacent composite plies. Such configurations were chosen because 1) practical implementation of this technology requires that sensors be embedded at arbitrary angles with respect to reinforcement fibre (i.e strain rosettes) and 2) the dearth of such studies available in the literature. Whatever studies were performed were in conflict in terms of accuracy reported. In addition, there are very few studies in which fibre optic sensors are either attached to the surface or embedded within realistically sized structures. Whenever these studies have been made found, fibre optic sensors have not been comprehensively validated according to a known standard. Fibre Bragg gratings (FBGs) and two types of Extrinsic Fabry Perot Interferometers (EFPI) are evaluated from the coupon level to large scale panels. Key questions identified in the literature are addressed. In general, FBGs are consistently 0-8% higher in magnitude, EFPI sensors from Fiso Technolgies are within 2-3%, and embedded EFPIs from Luna Innovations are ±3% compared with collocated strain gages. One of the most significant findings with this work, is that accurate measurements can be acquired with EFPI sensors embedded at a variety of configurations within composite structures. Overall, fibre optic sensor performance was determined to be a viable technology for a wide variety of structural health monitoring applications. No deleterious effects on the structural performance was observed in any of the tests conducted in this investigation.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available