Effects of Crimp and Cross-Sectional Area on the Mechanical Properties of Wool Fibers

Abstract

Force-extension data for a large number of wool fibers of various types have been analyzed in detail by statistical methods in order to determine the effects of fiber crimp and cross-sectional area on mechanical behavior. During the initial stages of crimp removal, the extensional behavior is controlled by fiber bending; during later stages of crimp removal, this behavior is controlled by both fiber bending and extension. Finally, as the crimp removal approaches completion, the behavior is controlled by the exten sional modulus of the fiber. This modulus is perturbed by differential bending strains associated with crimp removal which act to decrease the modulus below that for an un crimped fiber. Generally good correlation has been found between visual estimates of crimp and mechanical estimates based on analysis of the low-extension region of the fotce-extension curve. The methods of crimp evaluation used indicate that within a group of fibers taken from the same Rambouillet sheep the crimp level increases with increasing fiber diameter, and among fibers taken from sheep of different breeds the crimp level decreases with increasing fiber diameter. It is also observed that the rupture properties, breaking stress and breaking extension. generally increase with increasing fiber diameter.