TENSILE MECHANICAL PROPERTY EVALUATION OF NATURAL AND EPOXIDE-TREATEDSILK FIBERS

Silkworm cocoon silk and spider major ampullate (drag line) silk exhib it macroscopic tensile properties that, while impressive in the contex t of polymer fibers, are highly variable. The variability is linked to the cross-sectional geometry being nonuniform: silk fiber cross secti on changes significantly over distances that are small compared to the scale on which diameters are averaged by typical characterization tec hniques. This characteristic must be taken into account when evaluatin g chemical treatments (in the present case infiltrating with crosslink able epoxide) that are aimed at improving strength or stiffness. The m agnitude of any change in mechanical property must be considered in re lation to the spread in values recorded prior to treatment. An apparen t improvement in the mean value of a tensile property may turn out to be statistically insignificant when compared to the standard deviation s associated with those data. Previous authors do not address this sim ple assessment of significance. (C) 1995 John Wiley & Sons, Inc.