Nondestructive evaluation of hidden damages in glass fiber reinforced plastic by using the terahertz spectroscopy


In this work, the terahertz (THz) spectroscopy system was used for the detecting and evaluation of hidden damages in a glass fiber reinforced plastic (GFRP). The interaction between THz and the GFRP was analyzed including the effects of reflecting, scattering and absorption of THz radiations with respect to the type of hidden damage. Both the transmission and reflective configurations were used to investigate the hidden damages including the delamination, fiber fracture and moisture absorption. Finally, the hidden damages inside of the composite laminates were successfully imaged simultaneously based on the time-domain spectroscopy of THz radiation. Additionally, the moisture absorption damage in the GFRP could be detected by analyzing of the frequency domain spectrum. It is expected that the developed THz nondestructive evaluation (NDE) technique can be widely used to evaluate the health of the composite structures.

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R s :

Reflectance for s-polarized THz wave

R p :

Reflectance for p-polarized THz wave

R :

Reflectance for THz wave

T :

Transmittance for THz wave

n 1 :

Refractive index of incidence materials

n 2 :

Refractive index of refraction materials

n :

Refractive index

θ 1 :

Incidence angle of THz wave

θ 2 :

Refractive angle of the THz wave

A :

Absorbance of refraction material

I 0 :

Initial power of THz wave

x :

Thickness of specimen

α :

Absorption coefficient of refractive materials

ɛ r :

Relative permittivity of the material

µ r :

Relative permeability of the material


  1. 1.

    Beardmore, P., “Composite Structures for Automobiles,” Compos Struct, Vol. 5, No. 3, pp. 163–176, 1986.

    Article  Google Scholar 

  2. 2.

    Asnafi, N., Langstedt, G., Andersson, C.-H., Östergren, N., and Håkansson, T., “A New Lightweight Metal-Composite-Metal Panel for Applications in the Automotive and Other Industries,” Thin-Walled Structures, Vol. 36, No. 4, pp. 289–310, 2000.

    Article  Google Scholar 

  3. 3.

    Beardmore, P. and Johnson, C., “The Potential for Composites in Structural Automotive Applications,” Composites Science and Technology, Vol. 26, No. 4, pp. 251–281, 1986.

    Article  Google Scholar 

  4. 4.

    Kapadia, A., “Non Destructive Testing of Composite Materials,” National Composites Network, pp. 1–4, 2007.

    Google Scholar 

  5. 5.

    Mangalgiri, P., “Composite Materials for Aerospace Applications,” Bulletin of Materials Science, Vol. 22, No. 3, pp. 657–664, 1999.

    Article  Google Scholar 

  6. 6.

    Stoik, C., Bohn, M., and Blackshire, J., “Nondestructive Evaluation of Aircraft Composites Using Reflective Terahertz Time Domain Spectroscopy,” NDT&E International, Vol. 43, No. 2, pp. 106–115, 2010.

    Article  Google Scholar 

  7. 7.

    Shull, P. J., “Nondestructive Evaluation: Theory, Techniques, and Applications,” CRC Press, 2016.

  8. 8.

    Summerscales, J., “Non-Destructive Testing of Fibre-Reinforced Plastics Composites,” Springer Science & Business Media, 1990.

  9. 9.

    Lee, Y.-S., “Principles of Terahertz Science and Technology,” Springer Science & Business Media, 2009.

  10. 10.

    Chan, W. L., Deibel, J., and Mittleman, D. M., “Imaging with Terahertz Radiation,” Reports on Progress in Physics, Vol. 70, No. 8, pp. 1325, 2007.

    Article  Google Scholar 

  11. 11.

    Wang, S. and Zhang, X. C., “Pulsed Terahertz Tomography,” Journal of Physics D: Applied Physics, Vol. 37, No. 4, pp. R1–R36, 2004.

    Article  Google Scholar 

  12. 12.

    Wietzke, S., Jordens, C., Krumbholz, N., Baudrit, B., Bastian, M., et al., “Terahertz Imaging: A New Non-Destructive Technique for the Quality Control of Plastic Weld Joints,” Journal of the European Optical Society-Rapid Publications, 2007.

    Google Scholar 

  13. 13.

    Anbarasu, A., “Characterization of Defects in Fiber Composites Using Terahertz Imaging,” M.Sc. Thesis, Georgia Institute of Technology, pp. 1–42, 2008.

    Google Scholar 

  14. 14.

    Png, G. M., “Terahertz Spectroscopy and Modelling of Biotissue,” Ph.D. Thesis, University of Adelaide, 2010.

    Google Scholar 

  15. 15.

    Im, K.-H., Hsu, D. K., Chiou, C.-P., Barnard, D. J., Jung, J.-A., et al., “Terahertz Wave Approach and Application on FRP Composites,” Advances in Materials Science and Engineering, Article ID: 563962, 2013.

    Google Scholar 

  16. 16.

    Stoik, C. D., Bohn, M. J., and Blackshire, J. L., “Nondestructive Evaluation of Aircraft Composites Using Transmissive Terahertz Time Domain Spectroscopy,” Optics Express, Vol. 16, No. 21, pp. 17039–17051, 2008.

    Article  Google Scholar 

  17. 17.

    Ryu, C.-H., Park, S.-H., Kim, D.-H., Jhang, K.-Y., and Kim, H.-S., “Nondestructive Evaluation of Hidden Multi-Delamination in a Glass-Fiber-Reinforced Plastic Composite Using Terahertz Spectroscopy,” Composite Structures, Vol. 156, pp. 338–347, 2016.

    Article  Google Scholar 

  18. 18.

    Stoik, C. D., “Nondestructive Evaluation of Aircraft Composites Using Terahertz Time Domain Spectroscopy,” Optics Express, Vol. 16, No. 21, pp. 17039–17051, 2008.

    Article  Google Scholar 

  19. 19.

    Ferguson, B. and Zhang, X. C., “Materials for Terahertz Science and Technology,” Nature Materials, Vol. 1, No. 1, pp. 26–33, 2002.

    Article  Google Scholar 

  20. 20.

    Mittleman, D. M., Gupta, M., Neelamani, R., Baraniuk, R. G., Rudd, J. V., et al., “Recent Advances in Terahertz Imaging,” Applied Physics B, Vol. 68, No. 6, pp. 1085–1094, 1999.

    Article  Google Scholar 

  21. 21.

    Saeedkia, D., “Handbook of Terahertz Technology for Imaging,” Sensing and Communications, Elsevier, 2013.

    Google Scholar 

  22. 22.

    Xin, X., Altan, H., Saint, A., Matten, D., and Alfano, R. R., “Terahertz Absorption Spectrum of Para and Ortho Water Vapors at Different Humidities at Room Temperature,” Jouranl of Applied Physics, Vol. 100, No. 9, Paper No. 094905, 2006.

    Article  Google Scholar 

  23. 23.

    Swift, G. P., Dai, D., and Fletcher, J. R., “Terahertz Scattering: Comparison of a Novel Theoretical Approach with Experiment,” Proc. of International Society for Optics and Photonics in Integrated Optoelectronic Devices, 2006.

    Google Scholar 

  24. 24.

    Im, K.-H., Lee, K.-S., Yang, I.-Y., Yang, Y.-J., Seo, Y.-H., et al., “Advanced T-Ray Nondestructive Evaluation of Defects in FRP Solid Composites,” Int. J. Precis. Eng. Manuf., Vol. 14, No. 6, pp. 1093–1098, 2013.

    Article  Google Scholar 

  25. 25.

    Rutz, F., Koch, M., Khare, S., Moneke, M., Richter, H., et al., “Terahertz Quality Control of Polymeric Products,” International Journal of Infrared and Millimeter Waves, Vol. 27, No. 4, pp. 547–556, 2006.

    Article  Google Scholar 

  26. 26.

    Park, J.-W., Im, K.-H., Yang, I.-Y., Kim, S.-K., Kang, S.-J., et al. “Terahertz Radiation NDE of Composite Materials for Wind Turbine Applications,” Int. J. Precis. Eng. Manuf., Vol. 15, No. 6, pp. 1247–1254, 2014.

  27. 27.

    Yang, T., Brown, R., Kempel, L., and Kofinas, P., “Controlled Synthesis of Core-Shell Iron-Silica Nanoparticles and their Magneto-Dielectric Properties in Polymer Composites,” Nanotechnology, Vol. 22, No. 10, Paper No. 105601, 2011.

    Article  Google Scholar 

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Correspondence to Hak-Sung Kim.

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Kim, D., Ryu, C., Park, S. et al. Nondestructive evaluation of hidden damages in glass fiber reinforced plastic by using the terahertz spectroscopy. Int. J. of Precis. Eng. and Manuf.-Green Tech. 4, 211–219 (2017).

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  • Non-destructive evaluation
  • Glass fiber reinforced plastic
  • Delamination
  • Failure modes