Strength Improvement on an Imaginary SiC Fiber of Ideal Diameter and Reduced Internal Defects Estimated from the Weibull Scaling of Tyranno ZMI Fiber

The size effect of the diameter has been assessed for the tensile strength of Tyranno ZMI fiber. Uniform diameter section in sample fibers has been selected as tensile test sample. The single fibers of measured diameters have been tensile tested to provide two groups of data, i.e., “small diameter” group and “large diameter” group. The parameters of single-modal Weibull model showed inconsistency on the two groups, thus the Weibull parameters have shown the dependence on the sample diameter. Scanning electron microscope (SEM) analyses had revealed characteristic fracture patterns of “extremely weak” samples only in “large diameter” group. The key information for improving the reliability was then discussed through coupling the Weibull scaling and the fracture surface analyses. The potential in the strength improvement has been assessed for an imaginary fiber, which does not contain the sources of the characteristic fracture patterns.