Measuring orientation dynamics of carbon fibers by dielectric anisotropy in shear flows

Measuring orientation dynamics of carbon fibers is important for manufacturing high-performance composite materials, however, conventional methods fail to timely and non-destructively measure due to destructive sample preparation or complicated data processing from numerous fibers. Herein, we report a timely and non-destructive method that uses two pairs of interdigital electrodes to record dielectric anisotropy induced by carbon fibers orientation. As a proof-of-concept, orientation dynamics of carbon fibers is successfully characterized, the accuracy of which in measuring the final degree of orientation and dynamic orientation process is evidenced by theoretical calculations and optical observations. Experimental results reveal that increasing the fiber aspect ratios, viscosities of solvents and shear rates, could shorten orientation time or increase the final degree of orientation. Meanwhile, a modified model is proposed to explain orientation dynamics with a maximum error of 4.7%. This method has the potential for measuring the orientation dynamics of carbon fibers in the complex structure during processing.