Tuesday, 16 July 2013

Characterization of T-ray Penetration to Composite Materials

Kwang-Hee Im, David K. Hsu, Chien-Ping Chiou, Daniel J. Barnard and In-Young Yang

Department of Auto. Eng., Woosuk University 490, Samrae-up, Wanju-kun, Chonbuk, 565-701, Korea

Center for Nondestructive Evaluation, Iowa State University, Ames, Iowa 50011, USA

School of Mechanical Eng., Chosun University, 375 Seosuk-dong, Dong-gu, Kwangju 501-759, Korea

Using T-ray (Terahertz waves) characterization of the non-destructive evaluation was made on the penetration on composite materials. The modalities of the T-ray radiation used were time domain spectroscopy (TDS) and continuous wave (CW) for composites. The composite materials investigated include both non-conducting polymeric composites and carbon fiber composites. T-ray signals in the TDS mode resembles that of ultrasound; however, unlike ultrasound, T-ray pulse can detect a crack hidden behind a larger crack (shadow effect). Thick GFRP laminates containing double saw cuts was tested. Also, in carbon composites the penetration of T-ray waves was investigated in order to detect flawsis strongly affected by the angle between the electric field vector of the terahertz waves and the intervening fiber directions. The T-ray effect was intensively studied between the carbon fiber direction and the electric field of T-ray. Other composites tested in this study include both solid laminates and honeycomb sandwiches. The defects and anomalies investigated by T-ray were foreign material inclusions, simulated disbond and delamination, mechanical impact damage, and water or hydraulic fluid ingression. The intensive characterization of T-ray for the NDE of composites is being discussed.

... 2. T-ray system 2.1 T-ray scanner The terahertz instrumentation systems used in this research
were provided by TeraView Limited. The instrumentation includes a time domain spectroscopy
(TDS) pulsed system and a frequency domain continuous wave (CW) system. ...

Keywords: T-ray, Time domain spectroscopy, Composite materials, Penetration.