Direct Embedding of Fiber-Optical Load Sensors into Wind Turbine Blades

A Long-Period Grating Sensor forWind Turbine Blades

“…The objective was to perform applied research with LPGs demonstrating a competitive sensor technology to the traditional Fibre Bragg Grating (FBG) sensors and with much better selectivity sensing properties. The field of utilization of LPGs as sensors on wind turbine blades is new and this project has provided a review article on fibre grating sensors in wind turbines [108]. In addition the project has provided research regarding embedding of LPGs, in particular using special D-shape fibre, in the adhesive utilized in the matrix of a wind turbine blade and testing of these sensors on a full-scale wind turbine blade, and foresees the potential use of this technology in the future.…”

“…This indicated a uniform strain/stress influence from the adhesive under temperature changes, which is of significant importance for providing a spectral-response/shape suitable for sensing. Figure 40 -Normalized spectra of LPG at minimum and maximum temperature, from [108] The spectra were fitted to a polynomial and figure 41 shows a plot of the centrewavelength against the temperature, including a linear regression line. The spectral shift of the centre wavelength are approximately 6.8 nm/100°C and with a linear response (R 2 = 0.995).…”

Drug-Induced T-Wave Morphology Changesn

“…Note for a large scale production, recoating machines are commercialized (relative expensive). The recoated LPG was placed on a fiber-glass base-plate, and pre-fixed applying a small pre-strain (negligible wavelength shift), and embedded into the adhesive utilized in the matrix of a wind turbine blade [108]. Figure 38 shows the spectrum before and after embedding.…”

“…Therefore two FBGs were embedded with the adhesive together with a recoated LPG on a baseplate to investigate the influence from strain and temperature during the cure process and for temperature changes [108]. The setup is illustrated in figure 39.…”

“…The adhesive was cured with a standard production cure cycle. [108] During the curing process, the strain-effects were investigated with the two colocated FBGs. Using the mechanically decupled FBG as temperature sensor, the temperature influence was subtracted from the strain sensor.…”