Process Monitoring of CNT Composites by Optical Fibers

Abstract

CNT composites are promising materials due to the high-functions of electricity and damage resistance. In order to develop quality of CNT composites, it is necessary to improve dispersion of CNT because large CNT clusters grow easily. However, it is difficult to monitor growth of CNT clusters during molding. In the present paper, we proposed a new sensing method for the purpose by employing a refractive index measurement using an embedded optical fiber. This method utilized interference signals between Fresnel reflection from the distal end and Rayleigh scattering at the clusters. Only scattering lights, which include information of CNT clusters, can be obtained from the measured signals. From the experimental results, it appeared that the measured signals fluctuated largely when 0.077wt% of CNT exists in the resin. The amplitude of fluctuation of CNT composites was much larger than the carbon-black composites. It might be considered that the amplitude of fluctuation depend on the cluster size of fillers in composites.