Distributed Optical Sensing in Composite Laminate Adhesive Bonds

Meadows, Leeanna; Sullivan, Rani W.; Vehorn, Keith A.

doi:10.2514/6.2016-0239

Cited by 5 publications

(3 citation statements)

References 6 publications

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“…The rotated axis which aligns tangentially with the curvature of the DFOS path is denoted by . From past research studies [10,12,[23][24][25][26][27]29,34], it can be seen that the most effective way of placing the DFOS sensor to increase the sensing region was to lay it in a straight line and in the form of a semicircular geometry. Therefore, the strain transformation equation that is presented here deals with a semicircular fibre path geometry.…”

Section: Formulation Of Transformation Equationmentioning

confidence: 99%

“…Gifford et al [ 26 ] demonstrated applicability of DFOS as a strain rosette by bonding a single DFOS in a circular loop configuration to a metal test sample. Meadows et al [ 27 ] embedded DFOS in a double lap shear specimen and tensile tested them to obtain the strain response of the adhesive layer and to determine the impact of the sensor on the bond strength. Barker et al [ 28 ] integrated a sensor system comprising fibre optic sensors and strain gauges on the rail and bridge members of Newmarket bridge in Canada to measure the strain experienced by the bridge during the passing of trains.…”

Section: Introductionmentioning

confidence: 99%

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Distributed Fibre Optic Sensor-Based Continuous Strain Measurement along Semicircular Paths Using Strain Transformation Approach

Nagulapally¹,

Shamsuddoha²,

Rajan

et al. 2021

Sensors

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Distributed fibre optic sensors (DFOS) are popular for structural health monitoring applications in large engineering infrastructure because of their ability to provide spatial strain measurements continuously along their lengths. Curved paths, particularly semicircular paths, are quite common for optical fibre placement in large structures in addition to straight paths. Optical fibre sensors embedded in a curved path configuration typically measure a component of strain, which often cannot be validated using traditional approaches. Thus, for most applications, strain measured along curved paths is ignored as there is no proper validation tool to ensure the accuracy of the measured strains. To overcome this, an analytical strain transformation equation has been developed and is presented here. This equation transforms the horizontal and vertical strain components obtained along a curved semicircular path into a strain component, which acts tangentially as it travels along the curved fibre path. This approach is validated numerically and experimentally for a DFOS installed on a steel specimen with straight and curved paths. Under tensile and flexural loading scenarios, the horizontal and vertical strain components were obtained numerically using finite element analysis and experimentally using strain rosettes and then, substituted into the proposed strain transformation equation for deriving the transformed strain values. Subsequently, the derived strain values obtained from the proposed transformation equation were validated by comparing them with the experimentally measured DFOS strains in the curved region. Additionally, this study has also shown that a localised damage to the DFOS coating will not impact the functionality of the sensor at the remaining locations along its length. In summary, this paper presents a valid strain transformation equation, which can be used for transforming the numerical simulation results into the DFOS measurements along a semicircular path. This would allow for a larger scope of spatial strains measurements, which would otherwise be ignored in practice.

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Section: Formulation Of Transformation Equationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Distributed Fibre Optic Sensor-Based Continuous Strain Measurement along Semicircular Paths Using Strain Transformation Approach

Nagulapally¹,

Shamsuddoha²,

Rajan

et al. 2021

Sensors

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show abstract

“…In this study, an optical fiber (OF)-based strain measurement technique was tested on laminated composites to estimate the damage area. Previous studies using embedded OFs have been used to determine delamination growth 12,13 and the strain distributions in composite bonded joints 14 and in composite repair patches. 15 Most studies using OFs use fiber Bragg grating sensors for delamination detection and location in composites [16][17][18] and metals.…”

Section: Introductionmentioning

confidence: 99%

Impact response in polymer composites from embedded optical fibers

Batte

Sullivan

Ranatunga

et al. 2018

Journal of Composite Materials

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This study investigates the feasibility of using embedded optical fibers in polymer matrix composite laminates to characterize delaminations caused by low-velocity impacts with energies between 30 J and 50 J. Impact damage can occur in composite structures during manufacture, in-service, storage and routine maintenance. Because of their small size and light weight, optical fibers can be embedded in composite structures during the manufacture of composite parts, allowing the structure to be monitored for impact-induced delaminations without being removed from service. In this study, optical fibers are embedded in a grid configuration at four selected locations (one-third from impact surface, midplane, two-thirds from impact surface, and farthest ply from impact) in thick autoclave-cured graphite/epoxy laminates. Low-velocity impact testing is performed at four energy levels. Manufacturing procedures for embedding the optical fibers within the composite laminates are investigated. The strain distribution from the optical fibers is correlated with ultrasonic C-scans of the laminates in which they are embedded. X-ray computed tomography scan images are also compared to those from ultrasonic C-scans. Results indicate that embedded optical fibers can provide post-impact strain responses and delamination area from each embedded site within the impacted laminates.

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