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Proceedings Paper

High-precision thermal strain measurements using surface-mounted fiber Bragg grating sensors
Author(s): Uwe C. Mueller; Jan Both; Johannes Roths; Horst Baier
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Paper Abstract

Thermal strain measurements by fiber Bragg grating (FBG) sensors mounted onto different host materials are demonstrated for low coefficients of thermal expansion (CTE). Such low CTEs are typically found in carbon fiber reinforced plastics (CFRP). This work has application potential for FBG sensor networks in the highprecision control of thermal deformations in structures or in curing monitoring. For this purpose, a thermal error model of the FBG sensor, which accounts for the thermo-optic coefficient and the thermal expansion of the FBG, was characterized experimentally. The error-model characterization method is based on reference measurements of FBGs bonded to ZERODUR ceramics. Using this error model, thermal strain can be measured by surface-mounted FBGs on any given host structure using an external temperature reference and the FBG's wavelength shift. This method is demonstrated successfully for unidirectional layers of CFRP with a CTE of -0.4 · 10-6 1/K in fiber direction and for steel (316 Ti), which is commonly used in cryogenic applications. Measurements are performed for temperatures from 100K to 320K and the results are verified by high-precision dilatometer measurements. Accuracy limits of the FBG-based thermal strain measurements are discussed, as well as the minimization of errors induced by the FBG's structural interface. Further, the reduction of errors in the adhesive bonding is discussed. This work expands the understanding of the separation of thermal and mechanical effects in the signals obtained by FBGs.

Paper Details

Date Published: 7 April 2010
PDF: 12 pages
Proc. SPIE 7648, Smart Sensor Phenomena, Technology, Networks, and Systems 2010, 764807 (7 April 2010); doi: 10.1117/12.847535
Show Author Affiliations
Uwe C. Mueller, Technische Univ. München (Germany)
Jan Both, Technische Univ. München (Germany)
Johannes Roths, Hochschule München (Germany)
Horst Baier, Technische Univ. München (Germany)

Published in SPIE Proceedings Vol. 7648:
Smart Sensor Phenomena, Technology, Networks, and Systems 2010
Kara J. Peters; Wolfgang Ecke; Theodore E. Matikas, Editor(s)

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