THz and Thermal Wave Imaging for Material Inspection

In this paper, we discuss firstly the applicability of terahertz (THz) imaging systems to this purpose, focusing on graphite fiber composite materials, carbon silicon composite materials and so on. We apply THz imaging technology to evaluate fire damage to a variety of carbon fiber composite samples. Majority carbon fiber materials have polarization-dependent reflectivities in THz frequency range, and we show how the polarization dependence changes versus the burn damage level. Additionally, time domain information acquired through a THz time-domain spectroscopy (TDS) system provides further information with which to characterize the damage. We detect fuel tank insulation foam panel defects with pulse and CW terahertz system also. In this study, thermal wave was employed to map the through-thickness thermal diffusivity of specimens. Thermal wave provides the required fully integrated thermographic inspection system. This system has been approved as a nondestructive inspection method for use on the carbon composite. We study defects in metal, carbon fiber, glass fiber, carbon silicon composite and so on. The two image technologies are discussed in terms of nondestructive testing applications to the defense and aerospace industries.