Internal strain monitoring in composite materials with embedded photonic crystal fiber Bragg gratings

Thomas Geernaert; Sanne Sulejmani; Camille Sonnenfeld; Karima Chah; Geert Luyckx; Nicolas Lammens; Eli Voet; Martin Becker; Hugo Thienpont; Francis Berghmans

doi:10.1117/12.2061608

17 September 2014 Internal strain monitoring in composite materials with embedded photonic crystal fiber Bragg gratings

Thomas Geernaert, Sanne Sulejmani, Camille Sonnenfeld, Karima Chah, Geert Luyckx, Nicolas Lammens, Eli Voet, Martin Becker, Hugo Thienpont, Francis Berghmans

Author Affiliations +

Proceedings Volume 9226, Nanophotonics and Macrophotonics for Space Environments VIII; 92260D (2014) https://doi.org/10.1117/12.2061608
Event: SPIE Optical Engineering + Applications, 2014, San Diego, California, United States

Abstract

The possibility of embedding optical fiber sensors inside carbon fiber reinforced polymer (CFRP) for structural health monitoring purposes has already been demonstrated previously. So far however, these sensors only allowed axial strain measurements because of their low sensitivity for strain in the direction perpendicular to the optical fiber’s axis. The design flexibility provided by novel photonic crystal fiber (PCF) technology now allows developing dedicated fibers with substantially enhanced sensitivity to such transverse loads. We exploited that flexibility and we developed a PCF that, when equipped with a fiber Bragg grating (FBG), leads to a sensor that allows measuring transverse strains in reinforced composite materials, with an order of magnitude increase of the sensitivity over the state-of-the-art. In addition it allows shear strain sensing in adhesive bonds, which are used in composite repair patches. This is confirmed both with experiments and finite element simulations on such fibers embedded in CFRP coupons and adhesive bonds. Our sensor brings the achievable transverse strain measurement resolution close to a target value of 1 μstrain and could therefore play an important role for multi-dimensional strain sensing, not only in the domain of structural health monitoring, but also in the field of composite material production monitoring. Our results thereby illustrate the added value that PCFs have to offer for internal strain measurements inside composite materials and structures.

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Thomas Geernaert, Sanne Sulejmani, Camille Sonnenfeld, Karima Chah, Geert Luyckx, Nicolas Lammens, Eli Voet, Martin Becker, Hugo Thienpont, and Francis Berghmans "Internal strain monitoring in composite materials with embedded photonic crystal fiber Bragg gratings", Proc. SPIE 9226, Nanophotonics and Macrophotonics for Space Environments VIII, 92260D (17 September 2014); https://doi.org/10.1117/12.2061608

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