| 摘要 |
PROBLEM TO BE SOLVED: To obtain carbon fiber that has high mechanical properties, even when it has a high fiber thickness, and can increase flexural strength of the composite material by attaining a specific tensile modulus. SOLUTION: This filament satisfies the formula: YM>480-46.2r, when the cross section of the filament is assumed to be a perfect circle, and diameter of the filament cross section and the tensile modulus are represented by r (inμm) and YM (in GPa), or satisfies the formula: TS>9.18-1.02r, when the tensile strength is represented by TS (in GPa) and satisfies the formula: BS>=2270-1.87YM, when the tensile modulus and the flexural strength at 0 deg. of uni-direction carbon fiber-reinforced composite material are represented by YM (in GPa) and BS (in MPa). In a preferred embodiment, this carbon fiber has the flexual strength at 0 deg. in the uni-direction carbon fiber composite material correspondng to >=75% of the 0 deg. tensile strength, and the radius of the cross section of the filament is 4-10μm and the cross section has a tri- to penta-lobal form and contains boron in an amount of 50-5,000 ppm. |
