Research On Fatigue Resistance Of Fiber Grating Strain Sensor For Wind Turbine Blades

Wind turbine blade is an important core component of wind turbine to capture wind energy.With the large-scale structure of wind turbine blade,blade failure is more and more frequent.Fiber Bragg Grating(FBG)sensor has the advantages of corrosion resistance,anti electromagnetic interference,and can realize quasi distributed measurement for large structures,which makes the application of FBG in structural condition monitoring of wind turbine blade attracted attention.However,the light and thin non-metallic package,the loss of large capacity cascaded sensor network and the fatigue damage under long-term alternating load with large strain have become the problems of the wide application of optical fiber sensors in the field of wind power.In this paper,glass fiber reinforced polymer(GFRP)was used to package the FBG sensor,and the packaging process and performance optimization were studied to solve the engineering packaging problem of bare fiber Bragg grating with high fatigue resistance.The main contents of this paper are as follows:(1)the application status of embedded and composite substrate FBG sensors is introduced,and the transmission principle of optical fiber and the sensing mechanism of FBG are briefly described.On this basis,the types of structural damage of optical fiber and FBG,the mechanism of transmission attenuation loss of optical fiber and the corresponding influencing factors was analyzed.(2)The influence of packaging pressure and temperature parameters on the transmission attenuation loss of GFRP/fiber samples was analyzed.The packaging process parameters and packaging micro models with the least attenuation loss were obtained.The finite element simulation was used to analyze the stress of GFRP/fiber samples in the packaging process of different packaging mesoscopic models,which provided some guidance for the optimization of GFRP/fiber sensor packaging process.The influence of packaging pressure on the transmission attenuation loss of different packaging mesoscopic models GFRP/fiber samples was analyzed by experiments,and the minimum pressure and pressure mode of micro bending loss on the fiber were obtained,The GFRP/fiber samples were sealed by hot pressing under the pressure and pressure mode.The micro model of GFRP packaging with the minimum bending loss was obtained,and the FBG sensor is finally packaged.(3)A four-point bending fatigue test was carried out on the optimized GFRP/FBG sensor,and the fatigue life,test accuracy,sensitivity,linearity and repeatability errors of the GFRP/FBG sensor were analyzed through the strain test data to evaluate the anti-fatigue performance of the GFRP/FBG sensor.Finally,the GFRP/FBG sensor with the best anti-fatigue performance was pasted on the surface of wind turbine blades to conduct fatigue tests to verify the engineering applicability of the encapsulated GFRP/FBG sensor.