Abstract
Carbon-fiber-reinforced plastic (CFRP) composites are widely used in aerospace and concrete structure reinforcement due to their high strength and light weight. Terahertz (THz) time-domain spectroscopy is an attractive tool for defect inspection in CFRP composites. In order to improve THz nondestructive testing of CFRP composites, we have carried out systematic investigations of THz reflection and transmission properties of CFRP. Unidirectional CFRP composites with different thicknesses are measured with polarization directions 0 deg to 90 deg with respect to the fiber direction, in both reflection and transmission modes. As shown in the experiments, CFRP composites are electrically conducting and therefore exhibit a high THz reflectivity. In addition, CFRP composites have polarization-dependent reflectivity and transmissivity for THz radiation. The reflected THz power in the case of parallel polarization is nearly 1.8 times higher than for perpendicular polarization. At the same time, in the transmission of THz wave, a CFRP acts as a Fabry–Perot cavity resulting from multiple internal reflections from the CFRP–air interfaces. Moreover, from the measured data, we extract the refractive index and absorption coefficient of CFRP composites in the THz frequency range.
Highlights
The terahertz (THz) region lies between the microwave and infrared zones of the electromagnetic spectrum, with the frequency ranging from 0.1 to 10 THz.[1,2] In the past two decades, THz science and technology have been developed tremendously due to impressive improvements of ultrafast optoelectronics and low-dimensional semiconductor technology
The refractive index and absorption coefficient of Carbon-fiberreinforced plastic (CFRP) composites are obtained in this paper
We have conducted a systematic investigation of THz reflection and transmission properties of unidirectional CFRP composites with thin-layer structures (i.e., 1to 4-ply)
Summary
The terahertz (THz) region lies between the microwave and infrared zones of the electromagnetic spectrum, with the frequency ranging from 0.1 to 10 THz.[1,2] In the past two decades, THz science and technology have been developed tremendously due to impressive improvements of ultrafast optoelectronics and low-dimensional semiconductor technology. Carbon-fiberreinforced plastic (CFRP) laminates are useful composite materials. THz reflection and transmission properties of unidirectional CFRP composites with different thicknesses (e.g., 140 to 550 μm) are investigated systematically. Radiation depend on the angle between the fiber direction and electric field direction. When the fiber direction is parallel to the electric field direction, the THz reflected power of CFRP is fairly close to that of an aluminum metal plate while the transmitted power is relatively low. When the fiber direction is perpendicular to the electric field direction, the THz reflected power of CFRP is about half of that from the aluminum metal plate while the transmitted power is the highest compared with other angles. Concluding remarks and a summary are presented in the last section
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
