| 摘要 |
PROBLEM TO BE SOLVED: To provide a carbon fiber giving a composite material having excellent basic properties such as strength, especially compression strength, bending strength and the like, and excellent in a reinforcing effect, and to provide a method for manufacturing the same and a carbon fiber reinforced composite material. SOLUTION: The carbon fiber has a broad bean-type cross section in which the ratio a/b of the diameter (a) of the circumscribed circle to the diameter (b) of the inscribed circle is 1.5-2.5, a surface area ratio is <=1.05, and a strand strength after resin impregnation is >=4.5 Gpa. Manufacturing of the carbon fiber is carried out by a dry-wet spinning method using an acrylonitrile copolymer spinning dope in the following manner: drawing in a multi step temperature- elevation bath of a water/organic solvent-based solidifying medium, i.e., a 40-75 wt.% organic solvent containing aqueous solution at bath temperatures of -5 to 25 deg.C; and subsequently, imparting silicone oil, drying and compacting to obtain the carbon fiber.
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