Fiber Bragg grating (FBG) based sensors offer important advantages over traditional instrumentation with regards to real-time structural health monitoring (SHM) of composite materials and structures in recent years. F...Fiber Bragg grating (FBG) based sensors offer important advantages over traditional instrumentation with regards to real-time structural health monitoring (SHM) of composite materials and structures in recent years. FBG sensors, integrated into existing structures or embedded into new ones, have played a major role in assessing the safety and integrity of engineering structures. In this paper, a review on the latest research of the FBG-based SHM technique for composite field is presented. Firstly, the FBG sensing principle is briefly discussed and FBG and several other optical fiber sensors (OFSs) for SHM are performance-compared. Then, several examples of the use of FBG sensors in composite SHM are illustrated, including those from the field of cure monitoring, civil engineering, aviation, aerospace, marine and offshore platform. Finally, some existing problems are pointed out and some proposals for further researches are provided.展开更多
Fatigue behaviour has important implications for engineering composite structures in sectors ranging from automotive to aerospace.Optical sensing technology displays excellent performance in these fields for monitorin...Fatigue behaviour has important implications for engineering composite structures in sectors ranging from automotive to aerospace.Optical sensing technology displays excellent performance in these fields for monitoring.In this paper,temperature and residual strain during fatigue of a carbon fiber reinforced polymer(CFRP)are investigated.Four autoclaved CFRP beam specimens,with fiber Bragg grating(FBG)sensors and thermocouples embedded at selected locations,are subjected to three-point bending cyclic loading on the BOSE testing machine for fatigue testing.Thennocouples are used to measure the temperature while FBGs can sense the temperature and strain as well.Seven tests in total are conducted at different frequencies,and each test lasts for several days.From the experimental results,transient steep peaks of temperature increases(up to 2.3℃)are discovered at the beginning of the load.The following constant temperature increments are around 1.0℃,which is not relevant to frequencies from 0.1 Hz to 20 Hz and suspected due to fatigue.Residual strains of 1×10^-5-2×10^-5 during fatigue,fading away rapidly when unloading,are also reported.Embedded FBGs here are validated to sense temperature and strains in composite structures,which demonstrates promising potentials in structure monitoring fields.CFRP are verified to have an excellent performance during fatigue with low temperature increase and residual strain.展开更多
Running composite insulators are prone to failure due to their harsh surrounding work environment, which directly affects the safe operation of transmission lines. This paper puts forward the method of using fiber Bra...Running composite insulators are prone to failure due to their harsh surrounding work environment, which directly affects the safe operation of transmission lines. This paper puts forward the method of using fiber Bragg grating(FBG) as the monitors to parameters correlated with thermal and stress of the composite insulators in transmission lines at working status. Firstly, monitoring points are found out by the mechanical test on composite insulator samples. Secondly, based on the monitoring theory, this paper introduces the feasibility design frame of the composite insulator with FBG implanted in the rod and the online monitor system. At last, it describes applications of this monitor system in the field of transmission lines.展开更多
A novel multi-point sensing scheme to improve the signal-to-noise ratio(SNR),temperature measurement range of the fiber Bragg grating(FBG)sensors is proposed.The new sensing scheme adopted a composite coding technique...A novel multi-point sensing scheme to improve the signal-to-noise ratio(SNR),temperature measurement range of the fiber Bragg grating(FBG)sensors is proposed.The new sensing scheme adopted a composite coding technique based on Simplex codes and Golay codes and time division multiplexing technique to enhance the performance of the sensing system.Simulation results,in good agreement with the theory,confirmed that the maximum SNR enhancement of the sensor system employing composite coding based on 15-bit Simplex codes and 16-bit Golay codes was approximately 6.01 dB in comparison to the conventional single pulse case.展开更多
The interfacial performance of the Fiber Bragg grating（FGB） embedded in the composite was studied and the influence of interface modification on the final profile of the spectra of the FBG sensor was examined. A typ...The interfacial performance of the Fiber Bragg grating（FGB） embedded in the composite was studied and the influence of interface modification on the final profile of the spectra of the FBG sensor was examined. A type of polyamine（Pentaethylenehexamine, PEHA） was proposed to modify the coating of PI on FBG, and the interfacial performance was evaluated by a pull-out test. Sharp improvements of the interfacial shear strength（77%） were obtained by 40 min treatment of PEHA. Compared with untreated specimen, FGB spectra of treated specimen in the tensile tests show improved linearity within the test regime, which proves that the enhanced interface is beneficial for the sensing performance.展开更多
This paper reports on the design,fabrication,and temperature strain sensing performance of a fiber Bragg grating composite structure for surface mounted temperature measurements over a wide temperature range,with high...This paper reports on the design,fabrication,and temperature strain sensing performance of a fiber Bragg grating composite structure for surface mounted temperature measurements over a wide temperature range,with highly reduced strain cross-sensitivity.The fiber Bragg grating sensor is encapsulated in a polyimide tube filled with epoxy resin,forming an arc-shaped cavity.This assembly is then placed between two layers of glass fiber prepreg with a flexible pad in between and cured into shape.Experimental results,supported by finite element simulations,demonstrate an enhanced temperature sensitivity is 26.3 pm/°C over a wide temperature range of–30°C to 70°C,and high strain transfer isolation of about 99.65%.展开更多
In recent years, advanced composite structures are used extensively in many industries such as aerospace, aircraft, automobile, pipeline and civil engineering. Reliability and safety are crucial requirements posed by ...In recent years, advanced composite structures are used extensively in many industries such as aerospace, aircraft, automobile, pipeline and civil engineering. Reliability and safety are crucial requirements posed by them to the advanced composite structures be- cause of their harsh working conditions. Therefore, as a very important measure, structural health monitoring （SHM） in-service is deft- nitely demanded for ensuring their safe working in-situ. In this paper, fiber Bragg grating （FBG） sensors are surface-mounted on the hoop and in the axial directions of a FRP pressure vessel to monitor the strain status during its pressurization. The experimental results show that the FBG sensors could be used to monitor the strain development and determine the ultimate failure strain of the composite pressure vessel.展开更多
Pipelines are one of the most important modern energy transportation methods,used especially for the transportation of certain dangerous energy media materials such as crude oil,natural gas,and chemical raw materials....Pipelines are one of the most important modern energy transportation methods,used especially for the transportation of certain dangerous energy media materials such as crude oil,natural gas,and chemical raw materials.New requirements have been put forward for the health monitoring and early security warning of pipelines because of the large-scale and complicated development trend of the pipe network system.To achieve an accurate assessment of the health conditions of pipeline infrastructure,obtaining as many precise operating parameters as possible,particularly at some critical parts of the pipeline,is necessary.Therefore,a novel type of fiber grating strain sensor array is proposed herein to monitor the pipeline hoop strain.The sensor utilizes fiber grating characteristics such as light weight,corrosion resistance,remote transmission,and strong environmental adaptability.The fiber containing the grating measurement points is implanted into the composite material to complete the sensitization encapsulation and protection of the bare fiber grating.The design of the sensor array fulfills the requirements for monitoring pipeline mass data,making it easy to form a pipeline health monitoring sensor network.The sensor sensitivity is researched by using a combination of theoretical and experimental analysis.A sensitivity test,as well as linearity and stability tests,are performed on the sensor.The experimental results show that the average sensitivity of the sensor is 14.86 pm/με,and the error from the theoretical calculation analysis value is 8.75%.Due to its high reliability,good linear response and long-term stability,and the ability to reflect the exact strain change of the outer wall of the pipeline,the designed sensor can support longterm online pipeline monitoring.The fiber grating sensor array network has successfully realized the monitoring of the pipeline’s internal operation by using external strain changes.In addition to the performance benefits,there are other merits associated with the applicability of the sensor namely simple structure,compact size,manufacturing ease,and exterior installation ease.展开更多
In this paper a Fiber Bragg Grating (FBG) Strain Rosette is designed, developed and tested. Traditional FBGs measure strain in only one direction. However, in-plane strain at a point consists of two normal strains and...In this paper a Fiber Bragg Grating (FBG) Strain Rosette is designed, developed and tested. Traditional FBGs measure strain in only one direction. However, in-plane strain at a point consists of two normal strains and one shear strain. Hence a FBG strain rosette needs to be designed. The sensing principle of FBGs as a strain and temperature sensor and fundamental principles of strain transformation and strain gage rosettes are discussed.FBG strain rosettes are fabricated and embedded in two materials namely, Silicon Gel RTV 146-9 and Glass Fiber Composite Laminates. Experiments were conducted on the FBG strain rosette structures that were embedded in Silicon Gel (RTV 146-9). Initial findings from the experiments as well as preferred embedding material are presented.展开更多
Embedded fiber Bragg grating（FBG）sensors have been widely used for damage monkoring of fiber composite structures for a few decades.However,many remaining engineering challenges have delayed FBG based in situ struct...Embedded fiber Bragg grating（FBG）sensors have been widely used for damage monkoring of fiber composite structures for a few decades.However,many remaining engineering challenges have delayed FBG based in situ structural health monitoring（SHM）systems.One of the major problem associated with FBG based SHM system is the unavailability of reliable data processing algorithms.The present work details a study which has been undertaken for identification of delamination crack propagation in composite plate under fiber reinforced polymer（FRP）uniaxial loading.The strain measured by embedded FBG sensors closer to the crack tip was used to qualitatively and quantitatively analyze delamination damage propagation using recently proposed elasto-plastic model.Strain energy release rate was calculated and compared with the model prediction.The study has concluded that the delamination crack propagation in a FRP composite can be monitored successfully using an integral approach of FBG sensors measurements and the predictions of proposed elasto-plastic model.展开更多
There may be more than 2% strain of carbon fiber composite material on solid rocket motor （SRM） in some extreme cases. A surface-bonded silica fiber Bragg grating （FBG） strain sensor coated by polymer is designed ...There may be more than 2% strain of carbon fiber composite material on solid rocket motor （SRM） in some extreme cases. A surface-bonded silica fiber Bragg grating （FBG） strain sensor coated by polymer is designed to detect the large strain of composite material. The strain transfer relation of the FBG large strain sensor is deduced, and the strain transfer mechanism is verified by finite element simulation. To calibrate the sensors, the tensile test is done by using the carbon fiber composite plate specimen attached to the designed strain sensor. The results show that the designed sensor can detect the strain more than 3%, the strain sensitivity is 0.0762pm/με, the resolution is 13.13με, and the fitting degree of the wavelength-strain curve fitting function is 0.9988. The accuracy and linearity of the sensor can meet the engineering requirements.展开更多
In this paper,a novel liquid level sensor with ultra-high sensitivity is proposed.The proposed sensor is configured by a sliceshaped composite long period fiber grating(SSC-LPFG).The SSC-LPFG is prepared by polishing ...In this paper,a novel liquid level sensor with ultra-high sensitivity is proposed.The proposed sensor is configured by a sliceshaped composite long period fiber grating(SSC-LPFG).The SSC-LPFG is prepared by polishing two opposite sides of a composite multimode-single-mode-multimode fiber structure using a CO;laser.The method improves the sensitivity of the sensor to external environment.Based on the simulation calculation,a liquid level sensor with a length of 3 mm is designed.The experimental transmission spectrum agrees well with the simulation result.The experimental results show that the sensitivity reaches 7080 pm/mm in the liquid level range of 0-1400 μm in water.The temperature sensitivity is24.52 pm/℃ in the range of 20℃-90℃.Due to the ultra-high sensitivity,good linearity,and compact structure,the SSC-LPFG has potential application in the field of high-Drecision liquid level measurement.展开更多
The etching technique of the single-lined zero-thickness specimen grating is applied to the surface of the SiC fiber toughening Si3N4 ceramic composite specimen. The position of the crack and the crack length during t...The etching technique of the single-lined zero-thickness specimen grating is applied to the surface of the SiC fiber toughening Si3N4 ceramic composite specimen. The position of the crack and the crack length during the process of crack extension when the load is applied and gradually increased can be determined by recording the output voltage value of the Wheatstone bridge in which the ceramic specimen with the fracture grating on is located. The crack-growth-resistance(R-curve) of this material is thus obtained.展开更多
基金the National High Technology Research and Development Program (863) of China(No. 2011AA7052011)the National Natural Science Foundation of China (No. 51205253)
文摘Fiber Bragg grating (FBG) based sensors offer important advantages over traditional instrumentation with regards to real-time structural health monitoring (SHM) of composite materials and structures in recent years. FBG sensors, integrated into existing structures or embedded into new ones, have played a major role in assessing the safety and integrity of engineering structures. In this paper, a review on the latest research of the FBG-based SHM technique for composite field is presented. Firstly, the FBG sensing principle is briefly discussed and FBG and several other optical fiber sensors (OFSs) for SHM are performance-compared. Then, several examples of the use of FBG sensors in composite SHM are illustrated, including those from the field of cure monitoring, civil engineering, aviation, aerospace, marine and offshore platform. Finally, some existing problems are pointed out and some proposals for further researches are provided.
文摘Fatigue behaviour has important implications for engineering composite structures in sectors ranging from automotive to aerospace.Optical sensing technology displays excellent performance in these fields for monitoring.In this paper,temperature and residual strain during fatigue of a carbon fiber reinforced polymer(CFRP)are investigated.Four autoclaved CFRP beam specimens,with fiber Bragg grating(FBG)sensors and thermocouples embedded at selected locations,are subjected to three-point bending cyclic loading on the BOSE testing machine for fatigue testing.Thennocouples are used to measure the temperature while FBGs can sense the temperature and strain as well.Seven tests in total are conducted at different frequencies,and each test lasts for several days.From the experimental results,transient steep peaks of temperature increases(up to 2.3℃)are discovered at the beginning of the load.The following constant temperature increments are around 1.0℃,which is not relevant to frequencies from 0.1 Hz to 20 Hz and suspected due to fatigue.Residual strains of 1×10^-5-2×10^-5 during fatigue,fading away rapidly when unloading,are also reported.Embedded FBGs here are validated to sense temperature and strains in composite structures,which demonstrates promising potentials in structure monitoring fields.CFRP are verified to have an excellent performance during fatigue with low temperature increase and residual strain.
基金supported by National High-tech Research and Development Program of China (863 Program) (2013AA030701)Science and Technology Project of the State Grid Xinjiang Electric Power Corporation (5230DK15009L)
文摘Running composite insulators are prone to failure due to their harsh surrounding work environment, which directly affects the safe operation of transmission lines. This paper puts forward the method of using fiber Bragg grating(FBG) as the monitors to parameters correlated with thermal and stress of the composite insulators in transmission lines at working status. Firstly, monitoring points are found out by the mechanical test on composite insulator samples. Secondly, based on the monitoring theory, this paper introduces the feasibility design frame of the composite insulator with FBG implanted in the rod and the online monitor system. At last, it describes applications of this monitor system in the field of transmission lines.
基金Graduate Project Foundation of Shanghai Polytechnic University,China(No.A01GY18F022)
文摘A novel multi-point sensing scheme to improve the signal-to-noise ratio(SNR),temperature measurement range of the fiber Bragg grating(FBG)sensors is proposed.The new sensing scheme adopted a composite coding technique based on Simplex codes and Golay codes and time division multiplexing technique to enhance the performance of the sensing system.Simulation results,in good agreement with the theory,confirmed that the maximum SNR enhancement of the sensor system employing composite coding based on 15-bit Simplex codes and 16-bit Golay codes was approximately 6.01 dB in comparison to the conventional single pulse case.
基金Funded by the Fundamental Research Funds for the Central Universities(xjj2017160)the National Science and Technology Major Project(2014ZX04001091)
文摘The interfacial performance of the Fiber Bragg grating（FGB） embedded in the composite was studied and the influence of interface modification on the final profile of the spectra of the FBG sensor was examined. A type of polyamine（Pentaethylenehexamine, PEHA） was proposed to modify the coating of PI on FBG, and the interfacial performance was evaluated by a pull-out test. Sharp improvements of the interfacial shear strength（77%） were obtained by 40 min treatment of PEHA. Compared with untreated specimen, FGB spectra of treated specimen in the tensile tests show improved linearity within the test regime, which proves that the enhanced interface is beneficial for the sensing performance.
基金the financial support from Zhuzhou Times New Material Technology Co.LtD.(Grant No.XCFDJS-2022-00004495)Chilean National Agency for Research and Development(Basal FB0008).
文摘This paper reports on the design,fabrication,and temperature strain sensing performance of a fiber Bragg grating composite structure for surface mounted temperature measurements over a wide temperature range,with highly reduced strain cross-sensitivity.The fiber Bragg grating sensor is encapsulated in a polyimide tube filled with epoxy resin,forming an arc-shaped cavity.This assembly is then placed between two layers of glass fiber prepreg with a flexible pad in between and cured into shape.Experimental results,supported by finite element simulations,demonstrate an enhanced temperature sensitivity is 26.3 pm/°C over a wide temperature range of–30°C to 70°C,and high strain transfer isolation of about 99.65%.
文摘In recent years, advanced composite structures are used extensively in many industries such as aerospace, aircraft, automobile, pipeline and civil engineering. Reliability and safety are crucial requirements posed by them to the advanced composite structures be- cause of their harsh working conditions. Therefore, as a very important measure, structural health monitoring （SHM） in-service is deft- nitely demanded for ensuring their safe working in-situ. In this paper, fiber Bragg grating （FBG） sensors are surface-mounted on the hoop and in the axial directions of a FRP pressure vessel to monitor the strain status during its pressurization. The experimental results show that the FBG sensors could be used to monitor the strain development and determine the ultimate failure strain of the composite pressure vessel.
基金supported by the National Key R&D Program of China(Grants 2018YFF0214700)Hubei Province Science and Technology Special Major Project(2016AAA008)New Research and Development Agency Project of Zhongshan Science and Technology Bureau(2017F2FC003)in China.
文摘Pipelines are one of the most important modern energy transportation methods,used especially for the transportation of certain dangerous energy media materials such as crude oil,natural gas,and chemical raw materials.New requirements have been put forward for the health monitoring and early security warning of pipelines because of the large-scale and complicated development trend of the pipe network system.To achieve an accurate assessment of the health conditions of pipeline infrastructure,obtaining as many precise operating parameters as possible,particularly at some critical parts of the pipeline,is necessary.Therefore,a novel type of fiber grating strain sensor array is proposed herein to monitor the pipeline hoop strain.The sensor utilizes fiber grating characteristics such as light weight,corrosion resistance,remote transmission,and strong environmental adaptability.The fiber containing the grating measurement points is implanted into the composite material to complete the sensitization encapsulation and protection of the bare fiber grating.The design of the sensor array fulfills the requirements for monitoring pipeline mass data,making it easy to form a pipeline health monitoring sensor network.The sensor sensitivity is researched by using a combination of theoretical and experimental analysis.A sensitivity test,as well as linearity and stability tests,are performed on the sensor.The experimental results show that the average sensitivity of the sensor is 14.86 pm/με,and the error from the theoretical calculation analysis value is 8.75%.Due to its high reliability,good linear response and long-term stability,and the ability to reflect the exact strain change of the outer wall of the pipeline,the designed sensor can support longterm online pipeline monitoring.The fiber grating sensor array network has successfully realized the monitoring of the pipeline’s internal operation by using external strain changes.In addition to the performance benefits,there are other merits associated with the applicability of the sensor namely simple structure,compact size,manufacturing ease,and exterior installation ease.
文摘In this paper a Fiber Bragg Grating (FBG) Strain Rosette is designed, developed and tested. Traditional FBGs measure strain in only one direction. However, in-plane strain at a point consists of two normal strains and one shear strain. Hence a FBG strain rosette needs to be designed. The sensing principle of FBGs as a strain and temperature sensor and fundamental principles of strain transformation and strain gage rosettes are discussed.FBG strain rosettes are fabricated and embedded in two materials namely, Silicon Gel RTV 146-9 and Glass Fiber Composite Laminates. Experiments were conducted on the FBG strain rosette structures that were embedded in Silicon Gel (RTV 146-9). Initial findings from the experiments as well as preferred embedding material are presented.
文摘Embedded fiber Bragg grating（FBG）sensors have been widely used for damage monkoring of fiber composite structures for a few decades.However,many remaining engineering challenges have delayed FBG based in situ structural health monitoring（SHM）systems.One of the major problem associated with FBG based SHM system is the unavailability of reliable data processing algorithms.The present work details a study which has been undertaken for identification of delamination crack propagation in composite plate under fiber reinforced polymer（FRP）uniaxial loading.The strain measured by embedded FBG sensors closer to the crack tip was used to qualitatively and quantitatively analyze delamination damage propagation using recently proposed elasto-plastic model.Strain energy release rate was calculated and compared with the model prediction.The study has concluded that the delamination crack propagation in a FRP composite can be monitored successfully using an integral approach of FBG sensors measurements and the predictions of proposed elasto-plastic model.
文摘There may be more than 2% strain of carbon fiber composite material on solid rocket motor （SRM） in some extreme cases. A surface-bonded silica fiber Bragg grating （FBG） strain sensor coated by polymer is designed to detect the large strain of composite material. The strain transfer relation of the FBG large strain sensor is deduced, and the strain transfer mechanism is verified by finite element simulation. To calibrate the sensors, the tensile test is done by using the carbon fiber composite plate specimen attached to the designed strain sensor. The results show that the designed sensor can detect the strain more than 3%, the strain sensitivity is 0.0762pm/με, the resolution is 13.13με, and the fitting degree of the wavelength-strain curve fitting function is 0.9988. The accuracy and linearity of the sensor can meet the engineering requirements.
基金supported by the Joint Research Fund in Astronomy under cooperative agreement between the National Natural Science Foundation of China (NSFC) and Chinese Academy of Sciences (CAS) (Nos. U1831115, U2031132, U1931206, and U2031130)Natural Science Foundation of Heilongjiang Province (No. ZD2019H003)Fundamental Research Funds for the Central Universities to the Harbin Engineering University
文摘In this paper,a novel liquid level sensor with ultra-high sensitivity is proposed.The proposed sensor is configured by a sliceshaped composite long period fiber grating(SSC-LPFG).The SSC-LPFG is prepared by polishing two opposite sides of a composite multimode-single-mode-multimode fiber structure using a CO;laser.The method improves the sensitivity of the sensor to external environment.Based on the simulation calculation,a liquid level sensor with a length of 3 mm is designed.The experimental transmission spectrum agrees well with the simulation result.The experimental results show that the sensitivity reaches 7080 pm/mm in the liquid level range of 0-1400 μm in water.The temperature sensitivity is24.52 pm/℃ in the range of 20℃-90℃.Due to the ultra-high sensitivity,good linearity,and compact structure,the SSC-LPFG has potential application in the field of high-Drecision liquid level measurement.
文摘The etching technique of the single-lined zero-thickness specimen grating is applied to the surface of the SiC fiber toughening Si3N4 ceramic composite specimen. The position of the crack and the crack length during the process of crack extension when the load is applied and gradually increased can be determined by recording the output voltage value of the Wheatstone bridge in which the ceramic specimen with the fracture grating on is located. The crack-growth-resistance(R-curve) of this material is thus obtained.
