1993 年 42 巻 479 号 p. 955-961
Tensile tests for monofilament of carbon fiber were performed and the statistical distribution of tensile strength and its dependence on gauge length were investigated. Four types of carbon fibers produced from mesophase-pitch and polyacrylonitrile were tested. For each type of carbon fibers, 40 tensile tests were repeated for one gauge length, and three levels of gauge length were adopted in tests. Based on the statistical analysis of experimental results, it was found that the dependence of the fracture strength on gauge length was almost similar irrespective of the type of carbon fiber, and the size effect on the fracture strength showed anisotropy between the axial and radial directions. Variation of filament diameter had a considerable influence on the tensile strength. Anisotropy in the statistical distribution of tensile strength was numerically analyzed by using the distribution model of defect density and the Reynolds-Sharp criterion.