Abstract: An object of the present invention is to provide a carbon fiber which exhibits excellent strength development rate when used in a composite material. The present invention that solves the problems is a carbon fiber which simultaneously satisfies the following formulae (1) and (2): Lc/d?3??(1) TS×d×Lc>6.0×105??(2) wherein: Lc is an X-ray crystallite size (?), d is a filament diameter (?m), and TS is a strand tensile strength (MPa).

Abstract: A carbon fiber bundle having a high abrasion resistance property and simultaneously being excellent in widening property is provided by a carbon fiber bundle with an adhered sizing agent including a carbon fiber bundle, and a sizing agent adhered to a surface of the carbon fiber bundle, wherein the sizing agent contains an epoxy compound, and shows an intersection of a storage modulus and a loss modulus at an angular frequency in the range of 1×105 to 1×109 rad/sec in a measurement at 25° C.

Abstract: An object of the present invention is to provide a carbon fiber which exhibits excellent strength development rate when used in a composite material. The present invention that solves the problems is a carbon fiber which simultaneously satisfies the following formulae (1) and (2): Lc/d?3??(1) TS×d×Lc>6.0×105??(2) wherein: Lc is an X-ray crystallite size (?), d is a filament diameter (?m), and TS is a strand tensile strength (MPa).

Abstract: An object of the present invention is to provide a carbon fiber which exhibits excellent strength development rate when used in a composite material. The present invention that solves the problems is a carbon fiber which simultaneously satisfies the following formulae (1) and (2): Lc/d?3??(1) TS×d×Lc>6.0×105??(2) wherein: Lc is an X-ray crystallite size (?), d is a filament diameter (?m), and TS is a strand tensile strength (MPa).

Abstract: A method for manufacturing a precursor fiber bundle provides precursor fiber bundles used in manufacturing carbon fiber bundles allowing high productivity and having high tensile strength with less yarn bundle divides in the fiber bundles. The method for manufacturing a precursor fiber bundle includes spinning by extruding a spinning solution through a spinneret to produce a coagulated fiber bundle, and interlacing the coagulated fiber bundle by applying a fluid onto the coagulated fiber bundle. The interlacing includes applying the fluid (18) under a pressure in a range of 0.01 to 0.05 MPa onto the coagulated fiber bundle (14) with a moisture content in a range of 25 to 50% under a tension of 0.02 g/dtex or less.

Abstract: Method for producing a textile unidirectional fabric, wherein at least one planar layer of multi-filament reinforcement threads arranged parallel to each other are woven with each other over transverse threads, wherein transverse threads having core-sheath structure and titer of 10 to 40 tex are used as transverse threads, wherein transverse threads have a first component, which structures sheath, and second component, which structures core, wherein first component has lower melting temperature than second component, first component is meltable thermoplastic polymer material and, via first component of transverse threads, adjacently arranged multi-filament reinforcement threads are connected to each other by hot melting, wherein alleys are formed in unidirectional fabric by interweaving multi-filament reinforcement threads together with transverse threads, by means of which a permeability of 10 to 600 l/dm2/min can be established.

Abstract: Method for producing a textile unidirectional fabric, wherein at least one planar layer of multi-filament reinforcement threads arranged parallel to each other are woven with each other over transverse threads, wherein transverse threads having core-sheath structure and titer of 10 to 40 tex are used as transverse threads, wherein transverse threads have a first component, which structures sheath, and second component, which structures core, wherein first component has lower melting temperature than second component, first component is meltable thermoplastic polymer material and, via first component of transverse threads, adjacently arranged multi-filament reinforcement threads are connected to each other by hot melting, wherein alleys are formed in unidirectional fabric by interweaving multi-filament reinforcement threads together with transverse threads, by means of which a permeability of 10 to 600 l/dm2/min can be established.

Abstract: An object of the present invention is to provide a carbon fiber which exhibits excellent strength development rate when used in a composite material. The present invention that solves the problems is a carbon fiber which simultaneously satisfies the following formulae (1) and (2): Lc/d?3??(1) TS×d×Lc>6.0×105??(2) wherein: Lc is an X-ray crystallite size (?), d is a filament diameter (?m), and TS is a strand tensile strength (MPa).

Abstract: A carbon fiber strand obtained by bundling 20,000-30,000 carbon fibers each having, in the surface thereof, creases which are parallel to the fiber-axis direction. In an examination with a scanning probe microscope, the creases in the carbon fiber surface are apart from each other at a distance of 120-160 nm and have a depth of 12-23 nm, excluding 23 nm. The carbon fibers have an average fiber diameter of 4.5-6.5 nm, specific surface area of 0.9-2.3 m2/g, and density of 1.76 g/cm3 or higher. The carbon strand has a tensile strength of 5,900 MPa or higher and a tensile modulus of 300 GPa or higher. When would on a bobbin at a tension of 9.8 N, the strand on the bobbin has a width of 5.5 mm or larger. When the carbon fiber strand is examined by a strand splitting evaluation method in which the strand is caused to run through three stainless-steel rods while applying a tension of 9.8 N thereto, no strand splitting is observed.

Abstract: A carbon fiber strand which is produced by obtaining a solidified-yarn strand by spinning with a spinneret having 20,000-30,000 spinning holes, passing the strand through an interlacing nozzle having an air blowing pressure of 20-60 kPa to obtain precursor fibers, oxidizing them in heated air having a temperature of 200-280° C. to obtain oxidized fibers, subjecting these oxidized fibers to a first carbonization treatment in an inert-gas atmosphere at a temperature of 300-900° C. in which the fibers are firstly stretched in a stretch ratio of 1.03-1.06 and then secondarily stretched in a stretch ratio of 0.9-1.01, subsequently conducting a second carbonization treatment in an inert-gas atmosphere at 1,360-2,100° C., and then conducting a surface oxidization treatment in an aqueous solution of an inorganic acid salt in a quantity of electricity of 20-100 C per g of the carbon fibers.

Abstract: A carbon fiber strand obtained by bundling 20,000-30,000 carbon fibers each having, in the surface thereof, creases which are parallel to the fiber-axis direction. In an examination with a scanning probe microscope, the creases in the carbon fiber surface are apart from each other at a distance of 120-160 nm and have a depth of 12-23 nm, excluding 23 nm. The carbon fibers have an average fiber diameter of 4.5-6.5 nm, specific surface area of 0.9-2.3 m2/g, and density of 1.76 g/cm3 or higher. The carbon strand has a tensile strength of 5,900 MPa or higher and a tensile modulus of 300 GPa or higher. When would on a bobbin at a tension of 9.8 N, the strand on the bobbin has a width of 5.5 mm or larger. When the carbon fiber strand is examined by a strand splitting evaluation method in which the strand is caused to run through three stainless-steel rods while applying a tension of 9.8 N thereto, no strand splitting is observed.

Abstract: A carbon fiber strand which is produced by obtaining a solidified-yarn strand by spinning with a spinneret having 20,000-30,000 spinning holes, passing the strand through an interlacing nozzle having an air blowing pressure of 20-60 kPa to obtain precursor fibers, oxidizing them in heated air having a temperature of 200-280° C. to obtain oxidized fibers, subjecting these oxidized fibers to a first carbonization treatment in an inert-gas atmosphere at a temperature of 300-900° C. in which the fibers are firstly stretched in a stretch ratio of 1.03-1.06 and then secondarily stretched in a stretch ratio of 0.9-1.01, subsequently conducting a second carbonization treatment in an inert-gas atmosphere at 1,360-2,100° C., and then conducting a surface oxidization treatment in an aqueous solution of an inorganic acid salt in a quantity of electricity of 20-100 C per g of the carbon fibers.

Abstract: According to the present invention, there is disclosed a carbon fiber having a strand tensile strength of 6,100 MPa or more, a strand tensile modulus of 340 GPa or more and a density of 1.76 g/cm3 or more and possessing, on the surface, striations oriented in a direction parallel to the fiber axis, wherein the distance between striations in a 2×2 ?m area of the carbon fiber surface when observed by a scanning probe microscope is 0.1 to 0.3 ?m, the root mean square surface roughness Rms (5 ?m) in a 5×5 ?m area of the carbon fiber surface when observed by a scanning probe microscope is 20 to 40 nm, and the root mean square surface roughness Rms (0.5 ?m) when measured in a 0.5×0.5 ?m area is 2 to 12 nm.

Abstract: According to the present invention, there is disclosed a carbon fiber having a strand tensile strength of 6,100 MPa or more, a strand tensile modulus of 340 GPa or more and a density of 1.76 g/cm3 or more and possessing, on the surface, striations oriented in a direction parallel to the fiber axis, wherein the distance between striations in a 2×2 ?m area of the carbon fiber surface when observed by a scanning probe microscope is 0.1 to 0.3 ?m, the root mean square surface roughness Rms (5 ?m) in a 5×5 ?m area of the carbon fiber surface when observed by a scanning probe microscope is 20 to 40 nm, and the root mean square surface roughness Rms (0.5 ?m) when measured in a 0.5×0.5 ?m area is 2 to 12 nm.