In situ Strain and Temperature Monitoring of Adaptive Composite Materials

Temperature and strain discrimination is experimentally demonstrated in an elliptical-core polarization-maintaining fiber by making use of Rayleigh-based distributed birefringence measurements and the frequency shift of the correlation peak obtained by standard coherent optical time-domain reflectometry. The high sensitivity of coherent Rayleigh sensing and the very distinct behavior of birefringence makes the two quantities clearly discriminated, resulting in temperature and strain accuracies of ~ 40 mK and ~ 0.5 με, respectively, for distributed measurements with a 2 m spatial resolution.

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“…2. To reduce the error in the discrimination, a small conditional number is desired 9 . The number associated with Eq.…”

Section: Resultsmentioning

confidence: 99%

Discrimination of temperature and strain by combined refractive index and birefringence measurements using coherent Rayleigh sensing

Soto

Thévenaz

2017

SPIE Proceedings

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“…The temperature sensitivities of FBGs at 1552.3 nm, determined using the FiberPro interrogation unit, during the 1st and 2nd heat/cool cycles for the reference and coated FBGs were in the range of 9.7-9.9 pm K −1 respectively by considering a linear fit. The data reported in the literature for the temperature sensitivity of type-I Ge-B co-doped optical fibre grating was in the range of 9.19-10.69 pm K −1 [45,46]. Accepting the lower wavelength resolution of the FTNIR spectrometer when compared with the FiberPro interrogation unit, the corresponding temperature sensitivities for the coated and reference FBG sensors measured via the FTNIR spectrometer were in the range of 9.5-10.2 pm K −1 .…”

Section: Annealing the Au/pd Coatingsmentioning

confidence: 98%

Process monitoring of fibre reinforced composites using a multi-measurand fibre-optic sensor

Nair

Machavaram

Mahendran

et al. 2015

Sensors and Actuators B: Chemical

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a b s t r a c tThis paper reports on the design, fabrication, characterisation and deployment of a multi-measurand optical fibre sensor (MMS) that is capable of simultaneously monitoring strain, temperature, refractive index and cross-linking chemistry. The sensor design is based on the extrinsic fibre Fabry-Perot interferometer. A feature of this sensor system is that a conventional multi-channel fibre-coupled near-infrared spectrometer is used to monitor the four independent parameters. The issues relating to the measurement resolution of the individual sensors and the associated interrogation equipment are discussed. The MMS was embedded in between the fourth and fifth plies of an eight-ply E-glass plain-weave fabric. A commercially available thermosetting epoxy/amine resin system was used to impregnate the fabric layers manually. The laminated preform was vacuum-bagged and cured in an autoclave. The following parameters were monitored: the depletion rates of the epoxy and amine functional groups in the resin system; the temperature in close proximity to the "chemical sensor"; the evolution of strain; and the refractive index of the resin system. The effect of post-processing on the output from the embedded optical fibre sensors is also considered.

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“…, being S the norm of the matrix S containing the coefficients of sensitivities. In order to reduce the uncertainties in the discrimination, a small conditional number is desired [22]. Considering that the temperature and strain sensitivities of a φOTDR system are, in principle, similar to the ones of FBGs (i.e.…”

Section: Temperature-strain Discriminationmentioning

confidence: 99%

Temperature-strain discrimination in distributed optical fiber sensing using phase-sensitive optical time-domain reflectometry

Lu¹,

Soto²,

Thévenaz³

2017

Opt. Express

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A method based on coherent Rayleigh scattering distinctly evaluating temperature and strain is proposed and experimentally demonstrated for distributed optical fiber sensing. Combining conventional phase-sensitive optical time-domain domain reflectometry (ϕOTDR) and ϕOTDR-based birefringence measurements, independent distributed temperature and strain profiles are obtained along a polarization-maintaining fiber. A theoretical analysis, supported by experimental data, indicates that the proposed system for temperature-strain discrimination is intrinsically better conditioned than an equivalent existing approach that combines classical Brillouin sensing with Brillouin dynamic gratings. This is due to the higher sensitivity of coherent Rayleigh scatting compared to Brillouin scattering, thus offering better performance and lower temperature-strain uncertainties in the discrimination. Compared to the Brillouin-based approach, the ϕOTDR-based system here proposed requires access to only one fiber-end, and a much simpler experimental layout. Experimental results validate the full discrimination of temperature and strain along a 100 m-long elliptical-core polarization-maintaining fiber with measurement uncertainties of ~40 mK and ~0.5 με, respectively. These values agree very well with the theoretically expected measurand resolutions.

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In situ Strain and Temperature Monitoring of Adaptive Composite Materials

Cited by 28 publications

References 44 publications

Discrimination of temperature and strain by combined refractive index and birefringence measurements using coherent Rayleigh sensing

Discrimination of temperature and strain by combined refractive index and birefringence measurements using coherent Rayleigh sensing

Process monitoring of fibre reinforced composites using a multi-measurand fibre-optic sensor

Temperature-strain discrimination in distributed optical fiber sensing using phase-sensitive optical time-domain reflectometry

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