Application of Structural Similitude Theory in Subcomponent Testing of Wind Turbine Blades

摘要

Currently material selection for wind turbine blades is based upon initial coupon testing to evaluate mechanical properties (e.g. stiffness, delamination strength, fatigue durability) and also full-scale tests to benchmark the final design. However, the coupon testing is often not representative of the mechanical performance in full-scale blades, so time-consuming and very expensive full-scale tests are required to quantify the blade durability. Appropriate sub-component testing has the potential to bridge the gap between coupon and full-scale tests and to expedite the material characterization and structural optimization saving both time and money. In this study, the similarity conditions of an analytical model of a simply-supported plate analogous to the spar cap of a wind turbine blade are investigated with the objective of designing an applicable scaled down subcomponent. Based on direct use of the governing equations, bending of a specially orthotropic rectangular laminated plate under transverse loads is analyzed to extract the scaling laws. Theoretical maximum deflection of the subcomponent is mapped to the deflection of spar cap using scaling laws. Accuracy of the scaling laws in mapping the data is then used as a subcomponent design criteria and the effect of the ply stack up scheme and size of subcomponent are investigated by applying complete and partial similarity conditions. The results indicate that subcomponents with distortion in ply stack up can predict the maximum deflection of the prototype with good accuracy. However, using subcomponents with different aspect ratios than the prototype yield an inaccurate prediction of prototype response.