| 摘要 |
The invention aims to provide a carbon fiber bundle containing single-fibers having a quasi-oval cross-sectional shape so that the cause of an abnormality in strength, when it occurs, can be determined effectively. In the carbon fiber bundle, 40% or more of the single-fibers contained have a quasi-oval cross section perpendicular to the fiber direction and meet both Equations (1) and (2) given below: 1.03 ‰¤ La/Lb ‰¤ 1.20 (1) and 1.05 ‰¤ Ld/Lc ‰¤ 1.25 (2), wherein La is the length of the long axis which is defined as the line segment connecting the two points farthest away from each other on the circumference of the quasi-oval cross section of a single-fiber; Lb is the length of the short axis which is defined as the line segment extending perpendicular to the long axis, passing through the midpoint of the long axis, and connecting two points on the circumference; and when the long axis is divided into four equal parts to produce two line segments perpendicular to the long axis each of which passes through a point other than the midpoint of the long axis and connects two points on the circumference, Lc and Ld are defined as the length of the shorter one and that of the longer one, respectively. |
