A carbon fiber composite material includes the material is made of carbon fibers and a thermoplastic resin; the proportion Y, relative to the total weight of carbon fibers, of carbon fiber bundles for which Mn/(Ln×D) is 8.5×10.sup.−1 (mg/mm.sup.2) or more, is 30≦Y<90 (wt %); the average value X of Mn/Ln for the carbon fiber bundles is 1.1×10.sup.−2≦X≦8.1×10.sup.−2 (mg/mm); and Y satisfies Y≧100X+30, wherein Mn: weight of carbon fiber bundles, Ln: fiber length of carbon fibers, D: fiber diameter of carbon fibers. The carbon fiber composite material combines high flowability and mechanical properties, has few variations in mechanical properties and shows an excellent adaptability of carbon fibers for small parts such as ribs.

Methods of making fiber reinforced composite articles are described. The methods may include treating fibers with a sizing composition that includes a polymerization compound, and introducing the treated fibers to a pre-polymerized composition. The combination of the treated fibers and pre-polymerized composition may then undergo a temperature adjustment to a polymerization temperature at which the pre-polymerized composition polymerizes into a plastic around the fibers to form the fiber-reinforced composite article. Techniques for introducing the treated fibers to the pre-polymerized composition may include pultrusion, filament winding, reactive injection molding (RIM), structural reactive injection molding (SRIM), resin transfer molding (RTM), vacuum-assisted resin transfer molding (VARTM), long fiber injection (LFI), sheet molding compound (SMC) molding, bulk molding compound (BMC) molding, a spray-up application, and/or a hand lay-up application, among other techniques.

Methods of making fiber reinforced composite articles are described. The methods may include treating fibers with a sizing composition that includes a polymerization compound, and introducing the treated fibers to a pre-polymerized composition. The combination of the treated fibers and pre-polymerized composition may then undergo a temperature adjustment to a polymerization temperature at which the pre-polymerized composition polymerizes into a plastic around the fibers to form the fiber-reinforced composite article. Techniques for introducing the treated fibers to the pre-polymerized composition may include pultrusion, filament winding, reactive injection molding (RIM), structural reactive injection molding (SRIM), resin transfer molding (RTM), vacuum-assisted resin transfer molding (VARTM), long fiber injection (LFI), sheet molding compound (SMC) molding, bulk molding compound (BMC) molding, a spray-up application, and/or a hand lay-up application, among other techniques.

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.

Provided are a cellulose fiber containing cellulose II, the cellulose fiber having improved heat resistance, as well as a fiber reinforced resin composition, a method for producing the cellulose fiber, and a method for producing the fiber reinforced resin composition. The cellulose fiber contains the cellulose II having a content of an imidazolium salt of 1% by mass or less.

Provided are a cellulose fiber containing cellulose II, the cellulose fiber having improved heat resistance, as well as a fiber reinforced resin composition, a method for producing the cellulose fiber, and a method for producing the fiber reinforced resin composition. The cellulose fiber contains the cellulose II having a content of an imidazolium salt of 1% by mass or less.

Systems and methods for lightning strike materials are disclosed. The material may include a carbon fiber tow. Carbon nanotubes may be grown on carbon fibers within the carbon fiber tow. The carbon nanotubes may cause the carbon fibers to separate, decreasing a carbon tow fiber volume fraction of the tow. The growth of the carbon nanotubes may be controlled to select a tow fiber volume fraction of the tow. The lightning strike material may transmit electricity to decrease damage to the composite structure in case of a lightning strike.

Systems and methods for lightning strike materials are disclosed. The material may include a carbon fiber tow. Carbon nanotubes may be grown on carbon fibers within the carbon fiber tow. The carbon nanotubes may cause the carbon fibers to separate, decreasing a carbon tow fiber volume fraction of the tow. The growth of the carbon nanotubes may be controlled to select a tow fiber volume fraction of the tow. The lightning strike material may transmit electricity to decrease damage to the composite structure in case of a lightning strike.

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 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.