Carbon nanotube threads are coated with a coating solution such as dimethylformamide (DMF), ethylene glycol (EG), polyethylene glycol (PEG), PEG200 (PEG with a average molecular weight of approximately 200 grams per mole (g/mol)), PEG400 (PEG with a average molecular weight of approximately 400 g/mol), dimethyl sulfide (DMS 100 cP), HP1632, poly(methylhydrosiloxane), polyalkylene glycol, (3-aminopropyl)trimethoxysilane, hydride functional siloxane 0 resin, platinum (0) -1,3-divinyl-1,1,3,3-tetramethyl-disiloxane, moisture in air, acetic acid, water, poly(dimethylsiloxane) hydroxy terminated, (3-glycidyloxypropyl)-trimethoxysilane or a combination thereof. The coated carbon nanotubes may be used to stitch in a Z-direction into a composite such as a polymer prepreg to strengthen the composite. The stitching may occur using a sewing machine.

Provided are carbon fibers rich in surface functional groups, which has been recovered by thermolysis and anodization of a carbon-fiber-reinforced composite material. Also provided is a carbon-fiber-reinforced resin composition characterized by having excellent mechanical characteristics and an excellent surface appearance at a low cost as a result of using said carbon fibers.

Provided are a sizing agent coated carbon fiber bundle that has excellent mechanical characteristics when used as a carbon fiber reinforced composite material, as well as excellent ease of handling; a method for manufacturing the same; and a prepreg and carbon fiber reinforced composite material of excellent mechanical characteristics, employing the fiber bundle. The carbon fiber bundle is coated with a sizing agent that includes a polyether aliphatic epoxy compound having two or more epoxy groups per molecule and/or a polyol aliphatic epoxy compound or a non-water-soluble compound having a glass transition temperature of −100-50° C., wherein the sizing agent coated carbon fiber bundle is characterized in that the flatness ratio (width/thickness) of the carbon fiber bundle cross section is 10-150, and a two edge part/center part sizing agent deposition ratio, obtained by dividing the carbon fiber bundle in the width direction along the fiber direction into three equal parts by mass, and computing the ratio from the ratio of the mass of the sizing agent to the mass of the carbon fiber bundle in the center part and in both end parts, is 1.05-1.5.

A carbon fiber bundle for resin reinforcement, wherein there are adhered by 0.1-5.0 mass % to a carbon fiber bundle in which multiple lengths of filament are bundled, a mixture created by mixing an organic polymer (A) having a mass-average molecular weight of 10000 or more and an organic compound (B) the thermal reduction rate specified in claim 1 of which is 5 mass % or more or an organic compound (B) the thermal reduction rate specified in claim 2 of which is 0.8 mass % or more, the amount of the organic polymer (A) adhered being 0.1 mass % or more.

A bundle of carbon fibers has a value A obtained from a nonlinear approximation formula of a stress σ-strain ε curve in a tensile strength test of resin-impregnated strands and an orientation parameter H (%) of crystallites in a wide-angle x-ray diffraction measurement which satisfy a predetermined relational expression, and has tensile strength with a predetermined value or more, and tensile modulus within a predetermined range and a product E×d/W of a ratio d/W of a single-fiber diameter d to a loop width W just before loop fracture evaluated by a single-fiber loop test and a tensile modulus E of the strands has a predetermined value or more, or apparent single-fiber stress has a predetermined value or more when the number of fiber breaks by a single-fiber fragmentation method for a single-fiber composite is 0.30 breaks/mm and when the number of the fiber breaks by the single-fiber fragmentation method for the single-fiber composite is 0.30 breaks/mm, the number of fiber breaks by a double-fiber fragmentation method for the single-fiber composite is within a predetermined range.

A surface-treated carbon fiber having a mole ratio between a carboxyl group and an acid anhydride of 50:50 to 70:30 when measured by pyrolysis gas analysis, is manufactured by spraying a reactive gas that has been made into a plasma onto the surface of a carbon fiber and introducing a functional group into the surface of the carbon fiber.

A prepreg containing a carbon fiber [A] and a thermosetting resin [B], and in addition, satisfying at least one of the following (1) and (2). (1) a thermoplastic resin particle or fiber [C] and a conductive particle or fiber [D] are contained, and weight ratio expressed by [compounding amount of [C] (parts by weight)]/[compounding amount of [D] (parts by weight)] is 1 to 1000. (2) a conductive particle or fiber of which thermoplastic resin nucleus or core is coated with a conductive substance [E] is contained.

A process for fabricating a partially polymerized prepreg material. Fibers are impregnated with thermosetting resin. The resin is partially polymerized to a degree of polymerization between 10% and 60%. The thermosetting composite parts are produced by drape forming of the prepreg material. The material laid-up in the form of tapes and heated at a temperature above the glass transition temperature of the prepreg state. The laid-up material is pressed and cooled to return the laid-up material to a temperature below the glass transition temperature of the prepreg state in question.

Methods to increase structural performance, strength, and durability of textile-reinforced composite materials are provided. The textile reinforcement may be knitted, for example, in a flat bed weft knitting machine. The method may include pre-stressing a textile reinforcement preform by applying tension. A polymeric precursor may be introduced to the pre-stressed textile reinforcement preform. The polymeric precursor may then be cured or consolidated, followed by releasing of the applied tension to form the composite article comprising polymer and the pre-stressed textile reinforcement. In other aspects, a composite article is provided that has a pre-stressed textile reinforcement structure and a cured polymer. The textile reinforcement may be a knitted, lightweight, seamless, unitary structure. The knitted reinforcement structure may have distinct first and second knitted regions with different levels of pre-stress, thus providing enhanced control over strength, rigidity, and flexibility of the composite article.

Provided are a composite material and a reinforced fiber. The composite material includes a fiber and a plurality of carbon nanotubes disposed on a surface of the fiber. The carbon nanotubes adhere directly to the surface of the fiber.