In this paper, we present a study of detecting the hysteresis effect in strain-stress curve of carbon fiber reinforced
materials by Fiber Bragg Grating technology. By calculating the dissipative energy density contoured by hysteresis
loops, this method can be further applied in detecting the cracks and fatigue of carbon fiber reinforced laminates. In
contrast to the traditional sensors, such FBG sensors have numerous merits, such as small size, immunity to
Electromagnetic Interference and easy installation into the carbon fiber reinforced laminates. This method can also be
extended into monitoring other materials which also exhibit hysteresis effects in their strain-stress curves.
Leaking valves, connections and distribution pipelines are significant sources of fugitive gas and volatile chemical
emissions in chemical manufacturing, gas production, transmission, and oil refineries. A gas leak detection method has been developed based on continuous monitoring of the oxygen concentration surrounding a natural gas pipeline. The method utilizes optical fibers coated with an oxygen permeable polymeric film containing a luminescent sensor molecule. When the specialty fiber is illuminated by a light source that excites the luminophor, the functional
cladding compound has the ability to detect and quantify leaks by measuring small changes in oxygen concentrations in the surrounding environment. Key features of the technology include long-term performance based on well understood platinum porphyrin chemistry, in addition to the capability of distributed sensing using fiber optic
evanescent field spectroscopy. Results of leak detection in various environments namely atmospheric conditions, dry sand as well as saturated sand is reported, along with test results on long term system performance.
Results of research on real-time distributed monitoring of agents and products of materials deterioration will be presented. The potential of integration of functional polymers and optical wave-guides as tools for monitoring materials chemistries will be discussed. In such hybrid sensing systems, analyte recognition is carried out through the selection process inherent in the fiber optic poro-selective cladding materials, while transduction is carried out by the guided evanescent field which is spectrally modulated according to the level of the target analyte species present.
Fiber optic pH sensors based on the evanescent field spectroscopic technique is studied. Portions of poly (-methyl methacrylate) (PMMA) cladding of plastic clad silica (PCS) optical fibers are replaced with new cladding composed of PMMA doped with a pH sensitive chromophore. Methyl Red, Thymol Blue, Thymolphtalein are used for sensing pH at the acid, neutral and base levels. Changes in the pH of the analyte are detected by measuring the absorption spectrum of the new cladding in the sensing region of the optical fiber.
Conference Committee Involvement (7)
Nondestructive Characterization for Composite Materials, Aerospace Engineering, Civil Infrastructure, and Homeland Security VII
10 March 2013 | San Diego, California, United States
Nondestructive Characterization for Composite Materials, Aerospace Engineering, Civil Infrastructure, and Homeland Security VI
12 March 2012 | San Diego, California, United States
Nondestructive Characterization for Composite Materials, Aerospace Engineering, Civil Infrastructure, and Homeland Security V
7 March 2011 | San Diego, California, United States
Nondestructive Characterization for Composite Materials, Aerospace Engineering, Civil Infrastructure, and Homeland Security IV
8 March 2010 | San Diego, California, United States
Nondestructive Characterization for Composite Materials, Aerospace Engineering, Civil Infrastructure, and Homeland Security III
9 March 2009 | San Diego, California, United States
Advanced Environmental, Chemical, and Biological Sensing Technologies V
10 September 2007 | Boston, MA, United States
Health Monitoring and Smart NDE of Structural and Biological Systems V
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