Abstract: An apparatus and method for stretch breaking fibers wherein the formation of relatively small (lengths less than 30 microns) fractured fibers is substantially reduced. This reduction is achieved by applying a dampening fluid to the bundle of fibers during stretch breaking to dampen shockwaves generated during the fracturing process. The fractured fiber bundle may be subsequently treated with a sizing material to improve bundle cohesiveness and handling characteristics.

Abstract: Polyacrylonitrile (PAN)-based carbon fiber in the form of a filament bundle has a high Modulus and a high Tensile Strength in the Impregnated Strand Test respectively between about 42 million and 50 million psi and between about 600,000 and 900,000 psi, and Short Beam Shear Strength between about 15,000 and 19,000 psi in the Laminate Test; this PAN-based carbon fiber also has an electrolytically treated surface at 0.2 to 0.8 columbs per inch per approximate 12,000 filaments. The preparation of this PAN-based carbon fiber was accomplished by stretching during carbonization previously stretched and stabilized fine denier precursor while maintaining temperatures and heat up rates within certain ranges.