Abstract: There is disclosed a method of producing a pre-oxidation fiber in the production of the pre-oxidation fiber by subjecting a polyacrylic precursor fiber to pre-oxidation processing in an oxidizing atmosphere, including shrinking the precursor fiber as a pretreatment of pre-oxidation at a load of 0.58 g/tex or less in the temperature range of 220 to 260° C. under conditions in which the degree of cyclization (I1620/I2240) of the precursor fiber measured by a Fourier transform infrared spectrophotometer (FT-IR) does not exceed 7%, initially-drawing the precursor fiber at a load of 2.7 to 3.5 g/tex in an oxidizing atmosphere at 230 to 260° C. in the ranges of the degree of cyclization of not exceeding 27% and of the density of not exceeding 1.2 g/cm3, and then subjecting the pre-oxidation fiber to pre-oxidation treatment.

Abstract: The present invention relates to a carbon fiber having enhanced surface properties, tensile strength and tensile modulus to be able to obtain a composite material having high composite properties such as excellent impact resistance, preferably a carbon fiber of which tensile modulus is greater than or equal to 340 GPa and tensile strength is greater than or equal to 5970 MPa. The carbon fiber has the properties that the compression strength in the transverse direction of monofilament of the carbon fiber is greater than or equal to 130 kgf/mm2, the surface oxygen concentration (O/C) of the carbon fiber is in the range of 20 to 30%, and the value of the specific surface area of the carbon fiber based on a BET method by krypton absorption is in the range of 0.65 to 2.5 m2/g. The present invention also relates to a composite material including the carbon fiber and a matrix resin wherein the compression strength after impact is preferably greater than or equal to 220 MPa.

Abstract: There is disclosed a method of producing a pre-oxidation fiber in the production of the pre-oxidation fiber by subjecting a polyacrylic precursor fiber to pre-oxidation processing in an oxidizing atmosphere, including shrinking the precursor fiber as a pretreatment of pre-oxidation at a load of 0.58 g/tex or less in the temperature range of 220 to 260° C. under conditions in which the degree of cyclization (I1620/I2240) of the precursor fiber measured by a Fourier transform infrared spectrophotometer (FT-IR) does not exceed 7%, initially-drawing the precursor fiber at a load of 2.7 to 3.5 g/tex in an oxidizing atmosphere at 230 to 260° C. in the ranges of the degree of cyclization of not exceeding 27% and of the density of not exceeding 1.2 g/cm3, and then subjecting the pre-oxidation fiber to pre-oxidation treatment.