Measurement of stress concentrations using embedded optical fiber Bragg grating sensors

Kara J. Peters; Michel Studer; John Botsis; Alessandro Iocco; Hans G. Limberger; Rene-Paul Salathe

doi:10.1117/12.349730

31 May 1999 Measurement of stress concentrations using embedded optical fiber Bragg grating sensors

Kara J. Peters, Michel Studer, John Botsis, Alessandro Iocco, Hans G. Limberger, Rene-Paul Salathe

Author Affiliations +

Proceedings Volume 3670, Smart Structures and Materials 1999: Sensory Phenomena and Measurement Instrumentation for Smart Structures and Materials; (1999) https://doi.org/10.1117/12.349730
Event: 1999 Symposium on Smart Structures and Materials, 1999, Newport Beach, CA, United States

Abstract

This paper investigates the use of embedded optical fiber Bragg gratings to measure strain near a stress concentration within a solid structure. Due to the nature of a stress concentration (i.e. the strong non-uniformity of the strain field) the assumption that the grating spectrum in reflection remains a single peak with a constant bandwidth may not be valid. Compact tension specimens including a controlled notch shape are fabricated with embedded optical fiber Bragg gratings at identical locations but with different gauge lengths. The spectra in transmission varies between such specimens for given loading conditions. This variation is shown to be due to the difference in gauge length. By using the strain field measured on the specimen surface with electronic speckle pattern interferometry and a discretized model of the grating, the spectra in transmission are then verified analytically. Thus, by considering the non-uniformity of the strain field, the optical fiber Bragg gauge functions well as an embedded strain gauge near the stress concentration. Due to the distributed nature of the measurements within a specific gauge length, the optical fiber Bragg gauge has a large potential to measure debonding in fiber reinforced composites.

Citation Download Citation

Kara J. Peters, Michel Studer, John Botsis, Alessandro Iocco, Hans G. Limberger, and Rene-Paul Salathe "Measurement of stress concentrations using embedded optical fiber Bragg grating sensors", Proc. SPIE 3670, Smart Structures and Materials 1999: Sensory Phenomena and Measurement Instrumentation for Smart Structures and Materials, (31 May 1999); https://doi.org/10.1117/12.349730

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