Abstract: Chopped fiber strands are produced by (1) wetting a continuous unsized fiber tow with a volatile sizing agent, (2) chopping the wet fiber tow into predetermined lengths, and (3) exposing the chopped fibers to conditions of temperature and pressure that remove the sizing agent by volatilizing but do not cause any structural changes in the fiber. Bundles of the unsized fibers have a high bulk density and are easily dispersible in air or other media to individual filaments or groups of small numbers of individual filaments. The process is especially useful for producing high bulk density packages of polyacrylonitrile-based carbon fibers.

Abstract: Novel carbon fiber in the form of a plurality of tows or bundles comprising a multitude of continuous filaments is disclosed. The novelty of the carbon fiber resides in its unique combination of mechanical properties that make it admirably suited for use in composites comprising an organic matrix. Such composites are particularly useful in aerospace applications that have designs in which weight and performance are critical.

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.

Abstract: Process of carbon fiber manufacture wherein the polyacrylonitrile precursor is stretched prior to oxidation step of the carbonization operation but after the stretching step of the spinning operation in limited temperature range. Process permits greater throughput in precursor manufacture and reduces flaws in the precursor because significant stretching is at lower line speeds typically used for oxidation and carbonization in making carbon fiber.

Abstract: The adhesion between carbon fibers and unsaturated matrix resins used in the preparation of composite structures is improved by the use of an unsaturated epoxide bifunctional coupling agent. The coupling agent can be applied to the carbon fibers or incorporated into the matrix resin system.