Properties of a 37 m long FRP wind turbine blade after 11 years in service

The waste coming from decommissioned wind turbine blades poses an environmental problem since they are made primarily of Fiber Reinforced Polymers (FRPs) which are non-biodegradable materials. Millions of tons of these materials are expected to be disposed of in the coming years. Thus, responsible end-of-life (EOL) solutions are needed. The use of the blades for civil engineering infrastructure (e.g. power transmission poles, pedestrian bridge girders, highway sound barriers and roofing materials) has been proposed. In order to perform a structural and stress analysis for any of these design concepts, the as-received mechanical and physical properties of the specific type of wind blade to be used are needed. This paper presents an extensive testing program of the GFRP (Glass Fiber Reinforced Polymer) material in the spar cap of a 1.5 MW GE 37 decommissioned wind turbine blade that had been used for 11 years at a wind farm in Langford, Texas. Procedures for specimen preparation and testing are highlighted, since the blade parts have varying thicknesses (50 mm or more in some parts), layups and curvatures. As-received tensile, compressive, and shear strengths and stiffnesses were determined and compared to results from static testing of fatigued wind blades from the literature. Bolt testing was performed to obtain bearing and pull-through properties of the spar cap materials for second-life (i.e. EOL) applications where bolt performance will be a major design aspect.