An Effective Method to Inspect Adhesive Quality of Wind Turbine Blades Using Transmission Thermography

The wind turbine blade is one of the most important parts in a wind turbine system. The blade consists of a massive outer shell that is supported by an internal shear web with a thick layer of adhesive between them. Therefore the adhesive quality is a critical factor to guarantee it works properly for a designed service life of up to two decades. At present, it has been very challenging to evaluate the quality of this adhesive layer. In this study, a step-heating transmission thermography method was developed to measure the thickness variation of a blade shell, which was used for a quantitative evaluation of the adhesive quality. This method was verified first in a laboratory using three simulated blade specimens with wall thicknesses ranging from 13 to 31 mm. It was then used to inspect a 45.3 m wind blade. Based on the measured thickness distributions, an automated searching algorithm was developed to locate the adhesive edges which in turn determined the adhesive width and the adhesive-deficient area. The results obtained in this research demonstrated that the transmission thermography thickness measurement method is an effective way to evaluate the adhesive quality for wind turbine blades.