mail: merimoto.tetsuyaejaxajp lt is known that the singte-modal Weibu" medel describes well the size effect of brittle fiber tensile strength. However, some oeramie fibers have been reported that slngle-modal Weibull modet provided biased estimat;en en the gauge lengrh dependence. A hypothesis on the bias is that the density ef criticaE dofects is vety smail, thus, frecture prebebitity ef small gauge [ength samples distributes in dlscrete manner. vvhich makes the VVeibull parameters tiependent

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... n the gauge length, fyranno ZMI SFZFC-O fiber has been selected as an eecampie fiber. The tensile tests have been done on several gauge iengths. The derived Weibull parameters have shaArn a dependence on the gauge length for the case ef small gauge iength samples. Fracture svrfaces were observed with SEM. Then vve categorized the fracture surfhces by the charaeteristic fracture patterns, Percentage of each fracture pattern was found dependent en the gauge lengrh, tee.