High resolution fiber optic strain sensing is used to monitor the distributed strain during fatigue testing of a 9-meter CX-100 wind turbine blade with intentionally introduced defects.

High resolution fiber optic strain sensing is used to monitor the distributed strain during fatigue testing of a 9-meter CX-100 wind turbine blade with intentionally introduced defects.  Commercially available telecommunications-grade optical fiber was embedded in several layers of the carbon fiber spar cap and surface mounted along the spar cap and leading edges of the finished blade.  The amplitude and phase of the light reflected from the fibers are measured using a commercial Optical Frequency Domain Reflectometer (OFDR). Changes in the amplitude and phase of the backscattered light are used to determine the strain along the entire length of the fiber with 2.5 millimeter spatial resolution.  Distributed strain measurements throughout the depth of the spar cap provide an unprecedented view into the strain field within a composite wind turbine blade with defects during fatigue testing to failure.  

J. R. Pedrazzani et al., “Embedded and Surface Mounted Fiber Optics Sensors Detect Manufacturing Defects and Accumulated Damage as a Wind Turbine Blade is Cycled to Failure” SAMPE Tech. Conf. Proc.: Emerging Opportunities: Materials and Process Solutions, Baltimore, MD, 2012.