Terahertz imaging: a new non-destructive technique for the quality control of plastic weld joints

S. Wietzke; C. Jördens; N. Krumbholz; B. Baudrit; M. Bastian; M. Koch

doi:10.2971/jeos.2007.07013

Journal of the European Optical Society - Rapid publications, Vol 2 (2007)

Terahertz imaging: a new non-destructive technique for the quality control of plastic weld joints

S. Wietzke, C. Jördens, N. Krumbholz, B. Baudrit, M. Bastian, M. Koch

Abstract

We present the first investigation of plastic weld joints using terahertz waves. Terahertz time-domain spectroscopy clearly reveals contaminations like metal or sand within the weld joint of two high-density polyethylene sheets. Furthermore, areas can be identified where the welding process has failed and the parts to be joined are separated by a small air gap. We show that a three layer structure of polyethylene-air-polyethylene has a characteristic, frequency-dependent transmission behaviour. This allows for a distinction between welded and non-welded material as well as for the calculation of the air layer thickness from the relative transmission spectrum. Consequently, terahertz time-domain spectroscopy provides a promising new non-destructive and even contactless technique, which is desired by the plastics industry for detecting a variety of deviations from the ideal welding process.

Full Text: PDF

Citation Details

Cite this article

References

A. Benatar, "Introduction" in Plastics and Composites Welding Handbook, D. A. Grewell, A. Benatar, and J. B. Park, eds., 1-9 (Hanser, Munich, 2003).

C. Bonten and C. Tuechert, "Testing of weld joints" in Plastics and Composites Welding Handbook, D. A. Grewell, A. Benatar, and J. B. Park, eds., 361-392 (Hanser, Munich, 2003).

N. N., DVS 2203: Prüfen von Schweißverbindungen aus thermoplastischen Kunststoffen" (DVS, Düsseldorf, 1985-1999).

E. Pecha and A. Savitski, "Heated tool (hot plate) welding" in Plastics and Composites Welding Handbook, D. A. Grewell, A. Benatar, and J. B. Park, eds., 29-71 (Hanser, Munich, 2003).

B. B. Hu and M. C. Nuss, "Imaging with terahertz waves" Opt. Lett. 20, 1716-1718 (1995).

S. Hunsche, D. M. Mittleman, M. Koch, and M. C. Nuss, "New dimensions in t-ray imaging" IEICE T. Electron. E81-C, 269-276 (1998).

K. Kawase, Y. Ogawa, and Y. Watanabe, "Non-destructive terahertz imaging of illicit drugs using spectral fingerprints" Opt. Express 11, 2549-2554 (2003).

N. Karpowicz, H. Zhong, C. Zhang, K.-I. Lin, J.-S. Hwang, J. Xu, and X.-C. Zhang, "Compact continuous-wave subterahertz system for inspection applications" Appl. Phys. Lett. 86, 054105 (2005).

T. Kiwa, M. Tonouchi, M. Yamashita, and K. Kawase, "Laser terahertz-emission microscope for inspecting electrical faults in integrated circuits" Opt. Lett. 28, 2058-2060 (2003).

T. Yasui, T. Yasuda, K. Sawanaka, and T. Araki, "Terahertz paintmeter for noncontact monitoring of thickness and drying progress in paint film" Appl. Opt. 44, 6849-6856 (2005).

F. Rutz, M. Koch, S. Khare, M. Moneke, H. Richter, and U. Ewert, "Terahertz quality control of polymeric products" Int. J. Infrared Milli. 27, 547-556 (2006).

F. Rutz, T. Hasek, M. Koch, H. Richter, and U. Ewert, "Terahertz birefringence of liquid crystal polymers" Appl. Phys. Lett. 89, 221911 (2006).

Y. S. Jin, G. J. Kim, and S. G. Jeon, "Terahertz dielectric properties of polymers" J. Korean Phys. Soc. 49, 513-517 (2006).

D. M. Mittleman, ed., Sensing with Terahertz Radiation (Springer, Berlin/Heidelberg, 2003).

M. Herrmann, M. Tani, and K. Sakai, "Display modes in timeresolved terahertz imaging" Jpn. J. Appl. Phys. 1 39, 6254-6258 (2000).

S. Hunsche, M. Koch, I. Brener, and M.C. Nuss, "THz near-field imaging" Opt. Commun. 150, 22 (1998).

R. Wilk, M. Mikulics, K. Biermann, H. Künzel, I. Z. Kozma, R. Holzwarth, B. Sartorius, M. Mei, and M. Koch, "THz time-domain spectrometer based on LT-InGaAs photoconductive antennas exited by a 1.55 _m fibre laser" Conference on Lasers and Electro- Optics 2007, Baltimore, Maryland, May 2007.