Investigation of flaw strength distributions from tensile force-strain curves of fiber tows

Abstract

The flaw strength data are determined using tensile tests on various fiber tow types including, SiC, carbon, glass, basalt and alumina. The plots of p-quintile vs. flaw strength data derived from experimental force-strain curves exhibit linearity. This indicates unambiguously that flaw strength is a Gaussian variate. The statistical distribution of data was also calculated using the Weibull distribution function. Normal and Weibull cumulative distributions of flaw strengths are found to compare fairly well. The significance of normal distribution function and of the p-quintile vs. flaw strength relation for the characterisation of fibre flaw strength is discussed. The p-quintile vs. flaw strength relation is shown to provide theoretically a material characteristic. The normal distribution function is used to construct reference empirical distributions of flaw strengths that allow the evaluation of Weibull plot and Maximum Likelihood Estimation methods as functions of sample size and composition.