8th European Workshop On Structural Health Monitoring (EWSHM 2016)
5-8 July 2016, Spain, Bilbao
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Properties of optical fibers and FBG sensors and strain monitoring of the composite structures
Abstract »This paper is focused on determination of mechanical properties of optical fibers that are used for manufacturing of Fiber Bragg Grating (FBG) sensors and also on calibration of strain and temperature sensitivity of chosen FBG sensors. The goal of the experimental testing is to choose a FBG sensor with primary coating material, which is suitable for embedding into the composite or into the adhesive joints of composite structures (ultralight aircraft wing). Defining conditions for selection of FBG sensors are particularly max. temperature during the composite curing process (no more than 70 °C) and presumed level of max. mechanical strain in areas, where the FBG sensors will be installed (up to 6 000 µm/m). Another requirement was to use FBG sensors with central wavelength of 830 nm, because of available interrogators. Three types of primary coating materials, which are commonly used for manufacturing of FBG sensors, were considered. Properties of commercially available FBG sensors (in the most common optical windows of 830 nm and 1550 nm). Sensor with acrylate and ORMOCER® coating were selected for experimental testing. Safibra FBGuard 2-channel interrogator (CW 830 nm, sampling frequency of 70 Hz) was used to measure signal from FBG sensors during carried out using the biaxial tensile testing machine Zwick/Roell. Calibration values of strain and temperature sensitivity was investigated. Calibrated values of temperature and strain coefficients were used during the data evaluation process. Embedded FBG sensors were used for strain monitoring of cantilever wing beam during the bending load test. Composite wing was instrumented with FBG sensors for strain monitoring of spar caps and surface mounted strain gages. First optical fiber with chain of ten FBG sensors was embedded into the carbon/epoxy upper par cap during its manufacturing process. FBG sensors were oriented in a longitudinal axis, so the y can measure elongation/compression of the cap. Second optical fiber again with the chain of ten FBGs) was placed into the adhesive joint of the lower spar cap and shear web. Experiment confirmed the ability of integrated FBG sensors to survive production of the composite wing structure. Results from the bending load test show good agreement between the data evaluated from measurements from simple analytical model of wing load and from FE model.
AuthorsRuzicka, Milan*Ruzicka, Milan*
Milan RŮŽIČKA Head of the Department of Mechanics, Biomechanics and Mechatronics, Faculty of Mechanical Engineering, Czech Technical University in Prague, Czech Republic Prof. /Czech Techn. Univ. Prague/ 2005; PhD /Czech Techn. Univ. Prague/ 1984; Ing /Czech Techn. Univ. Prague/ 1979 Born 1955 Specialized in: applied and experimental mechanics, fracture mechanics and fatigue life prediction, mechanics of composites, structural health monitoring and smart structures. Author or co-author of more than 36 journal publications, 64 publications and contributions to international conferences, 5 univ. text books, 3 monographs. Society aff.: Danubia-Adria Symposium on Advances in Experimental Mechanics (inter. board member), European Workshop on Structural Health Monitoring (member, Steering Comm.), Czech Soc. for Mechanics (vice-chairman), Czech Soc. of Biomechanics (member) Business add.: Faculty of Mechanical Engineering, Czech Technical University in Prague, Technická 4, 166 07 Praha 6, Czech Republic Home: V Rovinách 52, 140 00 Praha 4, Czech Republic E-mail: Milan. Ruzicka@fs.cvut.cz Web page: http://web0.fsid.cvut.cz/en/home/
Czech Technical University in Prague, Fac. of Mech. Eng.
Dpt. of mechanics, biomechanics and mechatronics
16607 Praha 4
+420605242103Dvorak, MilanDvorak, Milan
Czech Technical University in Prague, Faculty of Mechanical Engineering (CTU FME)
Department Mechanics, Biomechanics and Mechatronics
166 07 Praha 6