On the Bulk Compression Characteristics of Wool Fibers

Abstract

A method has been found to prepare bulk samples of wool fibers in such a way that reproducible compression tests may be performed upon them. An evaluation of the bulk compression characteristics of 29 widely different wool samples shows that compressive load, rather than resilience, serves to bring out differences among them. This finding suggests that quality differences among wools, as determined by handling, are related to differences in the wools' resistance to compression rather than to differences in compressional resilience. For these 29 wool samples there is an inverse relationship between compressive load and mean fiber diameter. Although this finding is in agreement with similar results re ported for cotton fibers, it conflicts with the predictions from a theoretical model that has been proposed to explain the compressional behavior of wool. The theoretical model, which was based on a consideration of bending forces only during compression, has been claimed to fit results found for 310 samples of Merino wool. There is, therefore, an implication either that there is a different dependency of resistance to compression on fiber diameter within a wool breed as compared to that among different breeds or that the proposed theory is inadequate. When the compressing piston size is varied at a constant sample size for a Targhee 60's wool card sliver, it is found that the effective volume of fibers being compressed is greater than the volume of fibers beneath the piston, probably because of fiber-to-fiber entanglements. The experimental results indicate that a constant area should be added to the compressing piston areas in order to achieve a constant compressive stress. This area increment is independent of sample diameter, providing the sample diameter is suf ficiently greater than that of the compressing piston, and this area increment decreases with increasing degree of compression.