Paper number 899

THE WEIBULL MODULI OF SI-ZR-C-O FIBER WITH DIAMETER VARIATION ALONG THE GAUGE LENGTH.

T. Morimoto¹, R. M. Aoki²

1Aeroengines Division, National Aerospace Laboratory (NAL)
Jindaiji Higashi-machi 7-44-1, Chofu, Tokyo, 182-8522 Japan
2Institute for Structures and Design, German Aerospace Center (DLR)
Pfaffenwaldring 38-40, Stuttgart, 70569 Germany

Summary

Si-Zr-C-O ceramic fibers were evaluated for deriving the Weibull parameters of high accuracy. The approach in this study couples detailed measurements of the diameter along the gauge length with tensile tests. The distribution of critical defects is assumed in the two-parameter single-modal Weibull model to be homogeneous throughout the volume. In the case of ceramic fibers, the term of volume is usually replaced with gauge length assuming the uniformity of the diameter. However the diameter measurements revealed very large variation along the gauge length of each fiber. This affects the reliability of the Weibull parameters, if the parameters are correlated with the gauge length and not with the volume. Therefore, tensile samples of equal volume were made from the sections with negligible variation in the diameter. Then the Weibull moduli were calculated for the two-parameter single-modal case with the tensile results. The obtained results show that the two-parameter single-modal Weibull distribution can successfully characterize the strength of Si-Zr-C-O fibers.

Keywords

Weibull modulus, diameter variation, volume effect, Si-Zr-C-O fiber, tensile strength.