A dry aligning method of discontinuous carbon fibers and improvement of mechanical properties of discontinuous fiber composites

Abstract

A novel method for dry alignment of discontinuous carbon fibers, such as recycled carbon fibers was developed by the modification of the yarn manufacturing process. In order to achieve high production rate and application for long fibers, fluffy synthetic fibers were used as the suspending and carrying media for discontinuous carbon fibers instead of a fluid medium generally used. Using the mechanical interaction in the dry alignment method, a mixture of 200 mm long discontinuous carbon fibers and fluffy polypropylene fibers was fabricated into an aligned and homogeneously comingled sliver by drafting. Then, the sliver was spun into yarn and an aligned yarn preform was obtained. Composites, with approximately 70% of the fibers aligned within an angle of ±14° with respect to the drafting direction, were successfully produced from the preform of the aligned spun yarn. The tensile modulus of the composite specimen along the aligned direction was about 10 times larger than that along the transverse direction, and about 3.5 times larger than that for the specimens obtained from the same yarn with random orientation.