Non destructive inspection of wind turbine blades with three dimensional digital image correlation

Growing demand and deployment of wind power has led to a significant increase in the number of wind-turbine blades manufactured globally. As the physical size and number of turbines deployed grows, the probability of manufacturing defects being present in composite turbine blade fleets increases. As both capital blade costs, and operational and maintenance costs increase for large turbine systems, the need for large-scale inspection and monitoring of the state of structural health of turbine blades during manufacturing and operation increases.;One method for locating and quantifying manufacturing defects, while also allowing for the in-situ measurement of the structural health of blades, is three-dimensional digital image correlation (3D DIC). A nine-meter Sandia National Laboratories (SNL) CX-100 composite turbine blade was used as a platform for several experiments using 3D DIC. A quasi-static stepped loading test was performed on the blade to measure several damaged areas. The entire blade surface was measured with multiple fields of view in loaded and unloaded states. Post-processing of the data, using a stitching technique, enabled the surface strain and curvature of the entire high pressure surface of the blade to be measured, the first for a large-scale wind turbine blade.;An experiment was also developed to identify manufacturing defects within the CX-100 blade platform using 3D DIC as a non-destructive evaluation technique. Several tests were performed on composite coupon specimens and the full blade platform, including quasi-static and fatigue, to demonstrate the ability of the technique to detect manufacturing defects in a non-destructive way. Overall, the results indicate the measurement approach can identify failure locations, discontinuities in the blade curvature under load, elevated areas of strain, and manufacturing defects. The experiments exhibit the great potential of the optical measurement technique and its capability for use in the wind industry for large-area inspection.