Characterization of Staple Yarns By Acoustic Dynamic Modulus

The acoustic or sonic pulse-propagation technique for the measurement of dynamic elastic modulus has the advantage of not being dependent on the sample cross-sectional characteristics. This technique also gives a direct measure of modulus rather than the indirect measure in the form of load versus extension. The sonic tests are relatively simple to apply and are nondestructive. The values of sonic modulus of fibrous structures are dependent on the orientation of components and packing density as well. The main aim of this work is to quantify effect of yarn twist on the sonic modulus of staple yarns from polypropylene fibers. The results are compared with selected models of yarn twist influence on the mechanical properties of staple yarns. The correlation between yarn orientation factor defined by Pan and sonic modulus are shown. The sonic modulus is compared with tensile modulus of yarns.