Terahertz radiation study on FRP composite solid laminates

Abstract

Investigation of terahertz time domain spectroscopy (THz TDS) was made and reflection and transmission configurations were studied as a nondestructive evaluation technique. Here carbon fiber-reinforced plastics (CFRP) derived their excellent mechanical strength, stiffness and electrical conductivity from carbon fibers. Especially, the electrical conductivity of CFRP composites depends on the direction of unidirectional fibers since carbon fibers are electrically conducting while the epoxy matrix is not. The THz TDS can be considered as a useful tool using general non-conducting materials; however it is quite limited to conducting materials. In order to solve various material properties, the index of refraction (n) is derived by using the terahertz time domain spectroscopy. Also, for a 48-ply thermoplastic PPS(poly-phenylene sulfide)-based CFRP solid laminate, the terahertz scanning images were made at the angles ranged from 0° to 180° with respect to the nominal fiber axis. So, the images were mapped out based on the electrical field (E-field) direction in the CFRP solid laminates. ABSTRACT. Investigation of terahertz time domain spectroscopy (THz TDS) was made and reflection and transmission configurations were studied as a nondestructive evaluation technique. Here carbon fiberreinforced plastics (CFRP) derived their excellent mechanical strength, stiffness and electrical conductivity from carbon fibers. Especially, the electrical conductivity of CFRP composites depends on the direction of unidirectional fibers since carbon fibers are electrically conducting while the epoxy matrix is not. The THz TDS can be considered as a useful tool using general non-conducting materials; however it is quite limited to conducting materials. In order to solve various material properties, the index of refraction (n) is derived by using the terahertz time domain spectroscopy. Also, for a 48-ply thermoplastic PPS(poly-phenylene sulfide)-based CFRP solid laminate, the terahertz scanning images were made at the angles ranged from 0 o to 180 o with respect to the nominal fiber axis. So, the images were mapped out based on the electrical field (E-field) direction in the CFRP solid laminates.

Spectroscopic study of terahertz reflection and transmission properties of carbon-fiber-reinforced plastic composites

“…These results are in good agreement with previous studies. [15][16][17][18][19] Concomitantly, the THz transmission power increases when the angle between the fiber and electric field directions increases from 0 deg to 90 deg, which has not been convincingly demonstrated to date. Furthermore, the optical parameters (e.g., refractive index and absorption coefficient) of CFRP composites are obtained in this paper.…”

“…The first one was used to calculate the time delay based on the optical path length difference and can be solved by Eq. (1): [17][18][19] …”

“…Redo-Sanchez and Karpowicz 15 and Karpowicz and Dawes 16 applied THz continuous and pulsed wave technology in reflection mode to detect burn damage of CFRP. Im et al 17,18 and Park and Im 19 investigated the electrical field characterization in conducting carbon fiber. Additionally, a reflective THz time-domain spectroscopy (TDS) system was utilized to evaluate polyphenylene sulfide CFRP solid laminate with different angles of orientation of the carbon fibers.…”

Influence of terahertz waves on the fiber direction of CFRP composite laminates

“…The application of terahertz waves to the inspection of carbon composites is mentioned in the literature [8,11] but there has not been in depth studies. Carbon fiber reinforced polymer composites (CFRP) are poor conductors for electricity and the conductivity is anisotropic, so it is worthwhile to quantify the penetration of terahertz waves in carbon composites.…”

“…This method was to determine the index of refraction used to calculate the optical path length different between the front and back reflections in the time domain [11].…”