Non-Destructive and Contactless Defect Detection inside Leading Edge
Coatings for Wind Turbine Blades using Optical Coherence Tomography
Abstract
Leading edge erosion of wind turbine blades is one of the most critical
issues in wind energy production, resulting in lower efficiency, as well
as increased maintenance costs and downtime. Erosion is initiated by
impacts from rain droplets and other atmospheric particles, so to
protect the blades special protective coatings are applied to increase
their lifetime without adding significantly to the weight or friction of
the blade. These coatings should ideally absorb and distribute the force
away from the point of impact, however, microscopic defects, such as
bubbles, reduce the mechanical performance of the coating, leading to
cracks and eventually erosion. In this work, Optical Coherence
Tomography (OCT) is investigated for non-destructive, contactless
inspection of coated glass-fiber composite samples to identify
subsurface coating defects. The samples were tested using rubber
projectiles to simulate rain droplet and particle impacts. The samples
were subsequently imaged using both OCT, optical microscopy, and X-ray
tomography. OCT scanning revealed both bubbles and cracks below the
surface, which would not have been detected using ultrasonic or similar
non-destructive methods. In this way, OCT can complement the existing
quality control in turbine blade manufacturing, help improve the blade
lifetime, and reduce the environmental impact from erosion.