scholarly journals Environmental Durability of an Optical Fiber Cable Intended for Distributed Strain Measurements in Concrete Structures

Sensors ◽  
2021 ◽  
Vol 22 (1) ◽  
pp. 141
Author(s):  
Ismail Alj ◽  
Marc Quiertant ◽  
Aghiad Khadour ◽  
Quentin Grando ◽  
Karim Benzarti
Keyword(s):  
Mechanical Properties ◽  
Optical Fiber ◽  
Alkaline Solution ◽  
Accelerated Ageing ◽  
Bond Properties ◽  
Strain Measurements ◽  
Pull Out ◽  
Environmental Durability ◽  
Host Structure ◽  
Distributed Strain

The present study investigates the environmental durability of a distributed optical fiber sensing (DOFS) cable on the market, commonly used for distributed strain measurements in reinforced concrete structures. An extensive experimental program was conducted on different types of specimens (including samples of bare DOFS cable and plain concrete specimens instrumented with this DOFS cable) that were exposed to accelerated and natural ageing (NA) conditions for different periods of up to 18 months. The instrumentation of both concrete specimens consisted of DOFS cables embedded at the center of the specimens and bonded at the concrete surface, as these two configurations are commonly deployed in the field. In these configurations, the alkalinity of the surrounding cement medium and the outdoor conditions are the main factors potentially affecting the characteristics of the DOFS component materials and the integrity of the various interfaces, and hence impacting the strain transfer process between the host structure and the core optical fiber (OF). Therefore, immersion in an alkaline solution at an elevated temperature or freeze/thaw (F/T) and immersion/drying (I/D) cycles were chosen as accelerated ageing conditions, depending on the considered configuration. Mechanical characterizations by tensile and pull-out tests were then carried out on the exposed specimens to assess the evolution of the mechanical properties of individual component materials as well as the evolution of bond properties at various interfaces (internal interfaces of the DOFS cable, and interface between the cable and the host structure) during ageing. Complementary physico-chemical characterizations were also performed to better understand the underlying degradation processes. The experimental results highlight that immersion in the alkaline solution induced a significant and rapid decrease in the bond properties at internal interfaces of the DOFS cable and at the cable/concrete interface (in the case of the embedded cable configuration), which was assigned to chemical degradation at the surface of the cable coating in contact with the solution (hydrolysis and thermal degradation of the EVA copolymer component). Meanwhile, F/T and I/D cycles showed more limited effects on the mechanical properties of the component materials and interfaces in the case of the bonded cable configuration. A comparison with the same specimens exposed to outdoor NA suggested that the chosen accelerated ageing conditions may not be totally representative of actual service conditions, but provided indications for improving the ageing protocols in future research. In the last part, an analysis of the distributed strain profiles collected during pull-out tests on instrumented concrete specimens clearly illustrated the consequences of ageing processes on the strain response of the DOFS cable.

2504 Distributed Strain Measurements of Weld Joint by Optical Fiber Sensors

2007 ◽  
Vol 2007.6 (0) ◽  
pp. 209-210
Author(s):  
Kohei OHARA ◽  
Hideaki MURAYAMA ◽  
Kazuro KAGEYAMA ◽  
Isao OSAWA ◽  
Kiyoshi UZAWA ◽  
...  
Keyword(s):  
Optical Fiber ◽  
Weld Joint ◽  
Optical Fiber Sensors ◽  
Fiber Sensors ◽  
Strain Measurements ◽  
Distributed Strain

scholarly journals Distributed strain measurements using fiber Bragg gratings in small-diameter optical fiber and low-coherence reflectometry

2010 ◽  
Vol 18 (25) ◽  
pp. 26484 ◽  
Author(s):  
Dragan Coric ◽  
Marco Lai ◽  
John Botsis ◽  
Aiping Luo ◽  
Hans G. Limberger
Keyword(s):  
Optical Fiber ◽  
Fiber Bragg Gratings ◽  
Small Diameter ◽  
Bragg Gratings ◽  
Strain Measurements ◽  
Low Coherence ◽  
Distributed Strain

scholarly journals Comparison between Different Fiber Coatings and Adhesives on Steel Surfaces for Distributed Optical Strain Measurements based on Rayleigh Backscattering in Concrete Structures

2018 ◽  
Author(s):  
Martin Weisbrich ◽  
Klaus Holschemacher
Keyword(s):  
Optical Fiber ◽  
Steel Structures ◽  
Bending Test ◽  
Strain Measurements ◽  
Rayleigh Backscattering ◽  
Measurement Systems ◽  
Steel Surfaces ◽  
Optical Strain ◽  
Distributed Strain ◽  
Fiber Coatings

Optical fiber measurement systems have recently gained popularity following a multitude of intensive investigations. A new technique has been developed for these measurement systems that uses Rayleigh backscatter to determine the distributed strain measurement over the total length of a fiber. These measurement systems have great potential in civil engineering and structural health monitoring. This paper addresses some preliminary comparisons between three different fiber coatings and six different adhesives on steel structures. The results are based on a bending test with specimens made of precision flat steel; optical fiber strain measurements were compared with photogrammetric strain measurements. Analysis of the test data showed a strong correlation between the optical measurement system’s results and the theoretical results up to the yielding point of the steel. Furthermore, the results indicate that fibers with the Ormocer® and polyimide coatings have almost no loss in the strain measurements. The main results of this investigation are a guideline describing how to attach optical fibers to steel surfaces for distributed fiber optical strain measurements and recommendations for coatings to obtain realistic strain values. Additionally, the advantages of distributed strain measurements were revealed, which illustrates the potential of Rayleigh backscattering applications.

SYNTHESIS OF NANOSPHERICAL AND ULTRALONG FIBROUS HYDROXYAPATITE AND REINFORCEMENT OF BIODEGRADABLE CHITOSAN/HYDROXYAPATITE COMPOSITE

2009 ◽  
Vol 23 (31n32) ◽  
pp. 3967-3976 ◽  
Author(s):  
HUIGANG ZHANG ◽  
QINGSHAN ZHU
Keyword(s):  
Mechanical Properties ◽  
Polymer Composites ◽  
Alkaline Solution ◽  
Polyacrylic Acid ◽  
Bending Strength ◽  
Acidic Solution ◽  
Synthetic Route ◽  
Pull Out ◽  
Hydroxyapatite Composite ◽  
Long Fibers

Morphologies of hydroxyapatite (HAp) powders have influence on the mechanical properties of HAp/polymer composites. In this paper we reported a synthetic route for nanospherical and ultralong fibrous HAp powders and compared the influence of HAp morphologies on composite mechanical properties. HAp fibers with the length of ~250 µm along c-axis direction and nanospheres with the diameter of ~80 nm were produced, respectively, in the acidic solution containing glutamic acid and in the alkaline solution containing polyacrylic acid. The ultralong HAp fibers synthesized were used to reinforce biodegradable chitosan biomaterials with the significant improvement of bending strength because of the pull-out effect of long fibers.

scholarly journals Comparison between different fiber coatings and adhesives on steel surfaces for distributed optical strain measurements based on Rayleigh backscattering

2018 ◽  
Vol 7 (2) ◽  
pp. 601-608 ◽  
Author(s):  
Martin Weisbrich ◽  
Klaus Holschemacher
Keyword(s):  
Optical Fiber ◽  
Steel Structures ◽  
Bending Test ◽  
Strain Measurements ◽  
Rayleigh Backscattering ◽  
Measurement Systems ◽  
Steel Surfaces ◽  
Optical Strain ◽  
Distributed Strain ◽  
Fiber Coatings

Abstract. Optical fiber measurement systems have recently gained popularity following a multitude of intensive investigations. A new technique has been developed for these measurement systems that uses Rayleigh backscatter to determine the distributed strain measurement over the total length of a fiber. These measurement systems have great potential in civil engineering and structural health monitoring. This paper addresses some preliminary comparisons between three different fiber coatings and six different adhesives on steel structures. The results are based on a bending test with specimens made of precision flat steel; optical fiber strain measurements were compared with photogrammetric strain measurements. Analysis of the test data showed a strong correlation between the optical measurement system's results and the theoretical results up to the yielding point of the steel. Furthermore, the results indicate that fibers with the Ormocer® and polyimide coatings have almost the same strain values as the reference measurement method. The main results of this investigation are a guideline describing how to attach optical fibers to steel surfaces for distributed fiber optical strain measurements and recommendations for coatings to obtain realistic strain values. Additionally, the advantages of distributed strain measurements were revealed, which illustrates the potential of Rayleigh backscattering applications.

scholarly journals A Running Reference Analysis Method to Greatly Improve Optical Backscatter Reflectometry Strain Data from the Inside of Hardening and Shrinking Materials

2018 ◽  
Vol 8 (7) ◽  
pp. 1137 ◽  
Author(s):  
Søren Heinze ◽  
Andreas Echtermeyer
Keyword(s):  
Optical Fiber ◽  
Reference Value ◽  
Strain Differences ◽  
Ease Of Use ◽  
Analysis Method ◽  
Reference Analysis ◽  
Strain Measurements ◽  
Physical Conditions ◽  
The Difference ◽  
Distributed Strain

Due to the increasing ease of use and the superiority of the results, distributed strain measurements, utilizing Optical Backscatter Reflectometry (OBR), have become more important and widespread over the last few years. Strains are calculated from the difference between an actual optical Raleigh backscattering measurement and an initial reference value. However, under certain physical conditions, e.g., pinching or microbending of the optical fiber, no meaningful strain values are yielded by the commonly-used method to analyze OBR data. Such conditions were experienced in this study where the optical fiber was embedded into hardening epoxy for measuring shrinkage due to curing. In this work, it is shown that a new data analysis method called the “running reference analysis method” can overcome such obstacles and deliver meaningful strain values in circumstances in which the traditional method fails. In the new approach, each measurement is compared to the previous measurement, and the strain differences are added up to the absolute strain value. This method does not require a new experimental technique and will also work on old measurement files. It is also useful for other types of (OBR) strain measurements that contain many outliers and is not restricted to the investigation of cured epoxy.

Characterization of interfaces in CVD-coated nicalon fiber-reinforced SiC

1989 ◽  
Vol 47 ◽  
pp. 556-557
Author(s):  
K.L. More ◽  
R.A. Lowden
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Chemical Vapor ◽  
Chemical Vapor Infiltration ◽  
Frictional Stress ◽  
Fiber Reinforced ◽  
Pull Out ◽  
Carbon Coated ◽  
Fiber Matrix

The mechanical properties of fiber-reinforced composites are directly related to the nature of the fiber-matrix bond. Fracture toughness is improved when debonding, crack deflection, and fiber pull-out occur which in turn depend on a weak interfacial bond. The interfacial characteristics of fiber-reinforced ceramics can be altered by applying thin coatings to the fibers prior to composite fabrication. In a previous study, Lowden and co-workers coated Nicalon fibers (Nippon Carbon Company) with silicon and carbon prior to chemical vapor infiltration with SiC and determined the influence of interfacial frictional stress on fracture phenomena. They found that the silicon-coated Nicalon fiber-reinforced SiC had low flexure strengths and brittle fracture whereas the composites containing carbon coated fibers exhibited improved strength and fracture toughness. In this study, coatings of boron or BN were applied to Nicalon fibers via chemical vapor deposition (CVD) and the fibers were subsequently incorporated in a SiC matrix. The fiber-matrix interfaces were characterized using transmission and scanning electron microscopy (TEM and SEM). Mechanical properties were determined and compared to those obtained for uncoated Nicalon fiber-reinforced SiC.

scholarly journals Microstructure and Mechanical Performance of Resistance Spot Welded Martensitic Advanced High Strength Steel

Processes ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 1021
Author(s):  
Yunzhao Li ◽  
Huaping Tang ◽  
Ruilin Lai
Keyword(s):  
Mechanical Properties ◽  
Failure Modes ◽  
Mechanical Performance ◽  
Strong Dependence ◽  
High Strength ◽  
Weld Nugget ◽  
Resistance Spot ◽  
Pull Out ◽  
Cross Tension ◽  
Spot Welded

Resistance spot welded 1.2 mm (t)-thick 1400 MPa martensitic steel (MS1400) samples are fabricated and their microstructure, mechanical properties are investigated thoroughly. The mechanical performance and failure modes exhibit a strong dependence on weld-nugget size. The pull-out failure mode for MS1400 steel resistance spot welds does not follow the conventional weld-nugget size recommendation criteria of 4t0.5. Significant softening was observed due to dual phase microstructure of ferrite and martensite in the inter-critical heat affected zone (HAZ) and tempered martensite (TM) structure in sub-critical HAZ. However, the upper-critical HAZ exhibits obvious higher hardness than the nugget zone (NZ). In addition, the mechanical properties show that the cross-tension strength (CTS) is about one quarter of the tension-shear strength (TSS) of MS1400 weld joints, whilst the absorbed energy of cross-tension and tension-shear are almost identical.

Fiber Debonding Along a Crack Front in Paper

1998 ◽  
Vol 539 ◽  
Author(s):  
H. Kettunen ◽  
K. J. Niskanen
Keyword(s):  
Fracture Energy ◽  
Crack Front ◽  
Fracture Process ◽  
Fracture Process Zone ◽  
Process Zone ◽  
Bond Properties ◽  
Crack Line ◽  
Pull Out ◽  
Microscopic Damage ◽  
Debonding Process

AbstractWe follow the accumulation of microscopic damage ahead the crack tip in paper. The fiber debonding process varies even within each specimen because of large variation in fiber and bond properties. In general, stiff and weakly bonded fibers tend to debond as a rigid body while ductile or well bonded fibers pull out gradually in a process that propagates from the crack line to the fiber ends. Particularly in the latter case the network ruptures coherently rather than through debonding of single fibers. Experimental analysis and simulations show that fracture energy correlates closely with the size of the fracture process zone (FPZ) irrespective the nature of the debonding process. Only the cases of low bonding and stiff fibers seem to make an exception in that FPZ can grow in size without a corresponding increase in fracture energy.

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