Active Thermography for the Detection of Sub-Surface Defects on a Curved and Coated GFRP-Structure

Initial defects, for example, those occurring during the production of a rotor blade, encourage early damages such as rain erosion at the leading edge of wind turbine rotor blades. To investigate the potential that initial defects have for early damage, long-pulse thermography as a non-destructive a...

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Bibliographic Details
Published in:Applied sciences 2021-10, Vol.11 (20), p.9545
Main Authors: Jensen, Friederike, Terlau, Marina, Sorg, Michael, Fischer, Andreas
Format: Article
Language:English
Subjects:
active thermography
automatic defect detection
Coatings
Cooling
defect visualization
Defects
Glass fiber reinforced plastics
Inspection
leading edge
Leading edges
Measurement techniques
Nondestructive testing
Protective coatings
Rotor blades
Rotor blades (turbomachinery)
sub-surface defects
Thermography
Turbines
Viewing
Wind erosion
Wind power
wind turbine rotor blade
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Summary:Initial defects, for example, those occurring during the production of a rotor blade, encourage early damages such as rain erosion at the leading edge of wind turbine rotor blades. To investigate the potential that initial defects have for early damage, long-pulse thermography as a non-destructive and contactless measurement technique is applied to a strongly curved and coated test specimen for the first time. This specimen is similar in structural size and design to a rotor blade leading edge and introduced with sub-surface defects whose diameters range between 2mm and 3.5mm at depths between 1.5mm and 2.5mm below the surface. On the curved and coated test specimen, sub-surface defects with a depth-to-diameter ratio of up to 1.04 are successfully detected. In particular, defects are also detectable when being observed from a non-perpendicular viewing angle, where the intensity of the defects decreases with increasing viewing angle due to the strong surface curvature. In conclusion, long-pulse thermography is suitable for the detection of sub-surface defects on coated and curved components and is therefore a promising technique for the on-site application during inspection of rotor blade leading edges.
ISSN:2076-3417
2076-3417
DOI:10.3390/app11209545