Measuring changing strain fields in composites with Distributed Fiber-Optic Sensing using the optical backscatter reflectometer

Grave, Jon Harald Lambert; Håheim, Magnus Lund; Echtermeyer, Andreas T.

doi:10.1016/j.compositesb.2015.01.003

Cited by 63 publications

(34 citation statements)

References 15 publications

(9 reference statements)

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“…In [30], the reaction is described in more details. It should be mentioned that different types of epoxy were used in composite structures and the same OBR system yielded consistently successful strain results [32,33]. However, for the particular problem of cure shrinkage monitoring, only the above-mentioned epoxy system have been investigated thus far.…”

Section: Methodsmentioning

confidence: 99%

In-Situ Strain Measurements in Large Volumes of Hardening Epoxy Using Optical Backscatter Reflectometry

Heinze

Echtermeyer

2018

Applied Sciences

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Some large engineering structures are made by casting polymers into a mold. The structures can have complicated geometries and may be filled with other components, such as electrical transformers. This study investigated casting of large components made of epoxy. Epoxy is easy to pour, bonds well and has relatively low cure shrinkage. However, the cure shrinkage can lead to significant stresses or strains, causing large deformations that can lead to cracks.Understanding the curing process and related shrinkage is important for designing molds and controlling the production process. This study applied a new experimental method to measure strains due to cure shrinkage allowing many accurate local measurements along the length of an optical measurement fiber. The method is based on Optical Backscatter Reflectometry. Six distinct stages of the curing process can be identified. Previous measurements were limited to a few point measurements in small samples. This paper shows cure shrinkage in large samples and identifies some unexpected changes in behavior when going from small to large specimens. The behavior is explained qualitatively.

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Section: Methodsmentioning

confidence: 99%

In-Situ Strain Measurements in Large Volumes of Hardening Epoxy Using Optical Backscatter Reflectometry

Heinze

Echtermeyer

2018

Applied Sciences

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“…When an external stimulus (like strain or temperature variation) happens, a temporal and spectral shift in the local Rayleigh backscatter pattern occurs. This new reflection pattern is then compared with the original one providing the variation and evolution of generated strains along the entire length of the fiber due to this external stimulus (Grave et al, 2015). More detailed information of this technology can be consulted in Barrias et al (2016).…”

Section: Distributed Optical Fiber Sensorsmentioning

confidence: 99%

SHM of Reinforced Concrete Elements by Rayleigh Backscattering DOFS

Barrias

Casas

Villalba

2019

Front. Built Environ.

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This document showcases the latest research conducted within UPC-BarcelonaTech on the performance of distributed optical fiber sensors (DOFS), more specifically the case of the optical backscattered reflectometry (OBR) system, in the structural health monitoring (SHM) of bridges, and large scale structures. This technology has demonstrated promising results for monitoring applications in a wide range of fields but due to its novelty, still presents several uncertainties which prevent its use in a more systematic and efficient way in civil engineering infrastructures, being this even more evident in the case of concrete structures. Therefore, different laboratory experimental campaigns were devised where multiple aspects of the instrumentation of DOFS technology in civil engineering applications were assessed and scrutinized. Such as the study of new implementation methods, comparison, and performance analysis of different bonding adhesives and spatial resolution. Additionally, the fatigue performance of this sensing typology was also assessed. Furthermore, the use of the OBR system technology was applied in a real world structure in Barcelona, Spain, where new challenging conditions had to be addressed. Consequently, with this work, different conclusions are obtained related to the proficiency and limitations on the use of this particular type of optical sensing system in concrete structures.

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“…Grave et al further verified the functionality and performance of the OBR 4600. Grave concluded that the technology offered an excellent solution for measuring strain in non‐homogeneous strain fields.…”

Section: Methodsmentioning

confidence: 94%

Buckling due to external pressure of a composite tube measured by Rayleigh optical backscatter reflectometry and analyzed by finite elements

Hugaas

Vedvik

Echtermeyer

2018

Struct Control Health Monit

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Summary There is a growing interest in replacing steel tubes that operate in high pressure and high temperature environments with composite tubes. Such applications can include drilling risers and drill strings for the offshore oil industry. Replacing steel with composites in such applications will greatly reduce the weight of the equipment and require less buoyancy elements built into the structures. This paper seeks to investigate how composite tubes behave when submerged and how optical fibers can be used as a health monitoring system for such applications utilizing Rayleigh optical backscatter reflectometry. A glass fiber filament wound tube of 100 mm inner diameter and 600 mm length with a layup of approximately [89°, ±12.7°, ±45°] was exposed to external hydrostatic pressure in an autoclave. Optical fibers glued to the outer surface of the tube were used to measure strain during testing. A strain field reading was carried out every 0.5 bar pressure increase and correlated well with strain fields from a finite element analysis of the tube. The finite element analysis predicted buckling at 4.33 bar, assuming no material failure; however, the tube buckled at 3.5 bar due to a sudden stiffness reduction from material failure. The optical fibers could detect the early failure and functioned well as a health monitoring system.

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Measuring changing strain fields in composites with Distributed Fiber-Optic Sensing using the optical backscatter reflectometer

Cited by 63 publications

References 15 publications

In-Situ Strain Measurements in Large Volumes of Hardening Epoxy Using Optical Backscatter Reflectometry

In-Situ Strain Measurements in Large Volumes of Hardening Epoxy Using Optical Backscatter Reflectometry

SHM of Reinforced Concrete Elements by Rayleigh Backscattering DOFS

Buckling due to external pressure of a composite tube measured by Rayleigh optical backscatter reflectometry and analyzed by finite elements

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