Fiber Optic Sensor Systems For Smart Aerospace Structures

Dean, P. D.; Claus, Richard O.; Martin, David A.; Trites, D.

doi:10.1117/12.948887

Cited by 2 publications

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“…Figure 6 The data shows that trends or changes from the different salt solutions on the high index and low index fibers tend to be the same, though offset. Several conclusions were drawn from this data: (1) the high index fiber showed consistently greater loss than the low index fiber, which was expected since the higher index fiber supports higher order modes which were more strongly affected by changes at the surface of the core/cladding boundary, and the percentage power drop difference between the high and low index fiber was not greatly affected by small variations of refractive index of the medium regardless of whether it is above or below the index of the fiber, implying the losses were largely due to scattering.…”

Section: Testing Of High Index Fibers In Different Saltmentioning

confidence: 92%

<title>Aluminum alloy clad fiber optic corrosion sensor</title>

et al. 1997

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Life extension programs for military metallic aircraft are becoming increasingly important as defense budgets shrink and world economies realign themselves to an uncertain future. For existing military weapon systems, metallic corrosion damage costs an estimated $8 billion per year. One approach to reducing this cost is to develop a reliable method to detect and monitor corrosion in hidden metallic structure with the use of corrosion sensors which would give an early indication of corrosion without significant disassembly, thereby reducing maintenance costs. This presentation describes the development, analysis, and testing of a fiber optic corrosion sensor developed jointly with the Virginia Polytechnic Fiber & Electro-Optics Research Center and sponsored by Wright Laboratory Materials Directorate, contract #F33615-93-C-5368. In the sensor which was researched under this contract, the normal cladding is removed in the sensor region, and replaced with aluminum alloy and allowed to corrode on coupons representative of CIKC-135 body structure in an ASTM B 1 17 salt spray chamber and a Boeing developed Crevice Corrosion Cell. In this approach, the optical signal output of the sensor was originally designed to increase as corrosion takes place, however interaction with the corrosion byproducts yielded different results than anticipated. These test results to determine a correlation between the sensor output and the structural degradation due to corrosion are discussed.

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Section: Testing Of High Index Fibers In Different Saltmentioning

confidence: 92%

<title>Aluminum alloy clad fiber optic corrosion sensor</title>

et al. 1997

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<title>Novel methods for aircraft corrosion monitoring</title>

Bossi

Criswell

Ikegami

et al. 1995

Nondestructive Evaluation of Aging Aircraft, Airports, Aerospace Hardware, and Materials

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Monitoring aging aircraft for hidden corrosion is a significant problem for both military and civilian aircraft. Under a Wright Laboratory sponsored program, Boeing Defense & Space Group is investigating three novel methods for detecting and monitoring hidden corrosion: 1) atmospheric neutron radiography, 2) 14 MeV neutron activation analysis and 3) fiber optic corrosion sensors. Atmospheric neutron radiography utilizes the presence of neutrons in the upper atmosphere as a source for interrogation of the aircraft structure. Passive track-etch neutron detectors, which have been previously placed on the aircraft, are evaluated during maintenance checks to assess the presence of corrosion. Neutrons generated by an accelerator are used via activation analysis to assess the presence of distinctive elements in corrosion products, particularly oxygen. By using fast (14 MeV) neutrons for the activation, portable, high intensity sources can be employed for field testing of aircraft. The third novel method uses fiber optics as part of a smart structure technology for corrosion detection and monitoring. Fiber optic corrosion sensors are placed in the aircraft at locations known to be susceptible to corrosion. Periodic monitoring of the sensors is used to alert maintenance personnel to the presence and degree of corrosion at specific locations on the aircraft. During the atmospheric neutron experimentation, we identified a fourth method referred to as secondary emission radiography (SER). This paper discusses the development of these methods. INTRODUCTIONThe two primary damage mechanisms that limit the life of metallic aircraft structure are fatigue and corrosion. Corrosion has been found to be a problem that increases with age, particularly when the original design lifetime is exceeded. Experience has shown that corrosion can be managed but not eliminated, so detecting corrosion will remain an issue no matter how effective corrosion prevention programs become. A particularly costly concern is corrosion in hidden or inaccessible areas. In general, by the time corrosion is detected without disassembly, the damage is so extensive that massive repairs are required. Conversely, disassembly of these regions to inspect for the corrosion is time consuming and costly, particularly when there is no corrosion present. Further, disassembly often results in additional damage to the aircrafL Corrosion is the destructive attack of a metal by chemical or electrochemical reaction with its environment.The primary metals (aluminum and steel) in older aircraft are both prone to corrosion. In the presence of an appropriate electrolyte, these metals will convert, by an electrochemical process, to oxides and/or hydroxides. Being electrochemical, corrosion may be accelerated by either the presence of two different metals, such as a steel rivet in an aluminum hole, or by the passage of an electrical current, such as near the point of attachment of a grounding strap which is carrying current. Fortuitously, upon exposure to air, aluminum quickly form...

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Fiber Optic Sensor Systems For Smart Aerospace Structures

Cited by 2 publications

References 0 publications

<title>Aluminum alloy clad fiber optic corrosion sensor</title>

<title>Aluminum alloy clad fiber optic corrosion sensor</title>

<title>Novel methods for aircraft corrosion monitoring</title>

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