Abstract
Nowadays, smart composite materials embed miniaturized sensors for structural health monitoring (SHM) in order to mitigate the risk of failure due to an overload or to unwanted inhomogeneity resulting from the fabrication process. Optical fiber sensors, and more particularly fiber Bragg grating (FBG) sensors, outperform traditional sensor technologies, as they are lightweight, small in size and offer convenient multiplexing capabilities with remote operation. They have thus been extensively associated to composite materials to study their behavior for further SHM purposes. This paper reviews the main challenges arising from the use of FBGs in composite materials. The focus will be made on issues related to temperature-strain discrimination, demodulation of the amplitude spectrum during and after the curing process as well as connection between the embedded optical fibers and the surroundings. The main strategies developed in each of these three topics will be summarized and compared, demonstrating the large progress that has been made in this field in the past few years.
Highlights
Composite materials are obtained by assembling at least two non-miscible constituents that confer to the assembly physical properties not present in the constitutive materials taken alone [1]
As detailed in [29,38,39], tilted fiber Bragg grating (FBG) present a refractive index modulation slightly angled with respect to the perpendicular to the optical fiber axis, which couples light in the core and in the cladding
We first review the main techniques that are used to demodulate FBGs embedded into composite materials when they are subject to external perturbations
Summary
Composite materials are obtained by assembling at least two non-miscible (but presenting a high adhesion capability) constituents that confer to the assembly physical properties not present in the constitutive materials taken alone [1]. Among the different optical fiber configurations, fiber Bragg gratings (FBGs) photo-inscribed in the core of an optical fiber are the most widespread for use in composite materials [5] They correspond to a refractive index modulation of the fiber core along the fiber axis and behave as selective mirrors in wavelength. The present review complements well the one of [7] by bringing up-to-date references and by addressing two other relevant issues related the use of FBG strain sensors embedded into composite materials. For each of these three topics, the main solutions will be reviewed while their relative performances will be compared. The reader is invited to consult references [7,8,9] for details about these aspects
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