NDE characterization and inspection techniques of trailing edges in wind turbine blades using terahertz waves
Im, Kwang-Hee, Sun-Kyu Kim, Jong-An Jung, Young-Tae Cho, Yong-Deuck Wood, and Chien-Ping Chiou. “NDE characterization and inspection techniques of trailing edges in wind turbine blades using terahertz waves.” Journal of Mechanical Science and Technology 33, no. 10 (2019): 4745-4753.
Terahertz waves (T-ray) were extensively studied for the nondestructive evaluation of the characterization of trailing edges composed with composite materials. The NDE system consisted of both continuous wave (CW) and time domain spectroscopy (TDS). The FRP composites were utilized for both trailing edges of wind energy (non-conducting polymeric composites) and carbon fiber composites with conducting properties. The signals of T-ray in the TDS mode almost resembles that of ultrasound waves; however, a terahertz pulse could not penetrate a material with conductivity, unlike ultrasound. The refractive index (n) was utilized as one of the material properties, so a method was suggested to obtain the “n” in the materials. The data of refractive index (n) were utilized due to obtained data for the trailing edges. The trailing edges were scanned for charactering and inspecting. C-scan and B-scan images were obtained and the optimal NDE techniques were suggested for complicated geometry samples by terahertz radiation. In particular, the penetrating time-of-flight (TOF) of T-ray corresponded with the calculated TOF for the trailing edges with greater thickness (about 70 mm)…
… is an NDE equipment. This equipment is intended to obtain the material properties and property values of the sandwich test specimen. This experiment used a terahertz system manu- factured by TeraView (UK).