A case study on damage detection of wind turbine composite blade

In the entire wind turbine the most important part is the blade, which decides the power output by the virtue of size and shape. The design and material selection of a blade is very crucial since it constitutes the 20% of the total manufacturing cost of a whole wind turbine. To be specific, the blade material selection, manufacturing process, inspection and repair are very crucial in deciding the performance and life of the blade. Here we report the damage detection after manufacturing of turbine blade especially joints on the assembled blades by using latest techniques like infrared and ultrasonic inspection. The turbine blade is made up of glass reinforced plastic composite material manufactured by resin transfer moulding process with a length measuring up to 35.7 m. The infrared inspection method involves recording the variances in surface temperature due to heat generated by adhesive curing along bond lines. Using infrared images the type of defects like lack of adhesive webs, glue voids and uncured bonds are identified. Further inspection of adhesive joints between the blade shell and main webs and detection of its size is also carried out using ultrasonic B-scan method. The improper placing of web or hand lay-up laminate repair with improper bonding resulted signal loss. The defect thermographs and ultrasonic test scans of defects are also shown to show the accurate identification of the defects after manufacturing of a turbine blade. Finally the defects like dry laminate, delamination and wrinkles identified in the turbine blade are repaired following the appropriate methods and standards.