High Speed Yarn Production with Air-Jet Spinning: Effects of Some Fiber Parameters

This work is aimed at improving the quality of air-jet polyester/cotton blended yarns spun at a high delivery speed (285 m/min) and the fabrics produced from them. Short (28 mm) and fine (1.0 d) polyester fibers and combed cotton are used in an attempt to improve yarn strength and evenness. The possibility of increasing delivery speed when fine denier polyester is used is also investigated. Whereas fine polyester and combed cotton improve yarn strength, evenness, and imperfection level, short polyester fibers do not improve yarn evenness. Long polyester fibers improve a yarn's strength but lower its elongation, making it stiffer. Long, coarser polyester fibers and combed cotton lead to a higher number of long hairs. Fine polyester fibers increase the delivery speed without significant loss in yarn strength and evenness, but with a considerable deterioration in the yarn imperfection level and hairiness. Fabric abrasion resistance is higher for longer polyester and combed cotton fibers. While none of the variables influences fabric pilling resistance and compressional resilience, shorter polyester and carded cotton fibers promote higher compressional energy and reduce fabric thickness.

Compressional Energy of the Random Fiber Assembly

In this paper, we describe the method used to evaluate the theory of the compressional energy of the random fiber assembly, which was developed mathematically in Part I. We also introduce a mathematical derivation of the method for updating the orientation density function of fibers in a general fiber assembly. In order to evaluate the energy, the distribution of the fiber segment lengths is characterized using the gamma distribution. In addition, the curvature of the fiber segments is characterized by an equation that relates the crimp and the effective diameter of the crimped fiber configuration. We use minimization technique to compute the compressional energy. Effects of the mechanical properties of fibers and the structural parameters of the assembly on the minimum compressional energy are computed for New Zealand wools. Except for fiber crimp, there is good agreement between the computed results and experimental results for the various fiber and structural parameters. The model shows that if only fiber crimp is increased for a given initial geometry, the tangent compression modulus actually decreases. However, this point cannot be tested because crimpier fibers cannot be brought to the same initial geometry without generating nonzero compressional strain energy. We plan further investigation of this point.

Compressional Energy of the Random Fiber Assembly

The compressional mechanism of a random fiber assembly is analyzed by an energy method. An infinitesimal fiber segment, which is bounded by two neighboring contact points, is chosen as the unit bending element. The geometry of this element is characterized by its arc length, curvature, and orientation. The change in bending energy of each fiber segment due to the compression of the assembly is derived in terms of the compressional strain and the Poisson's ratio of the assembly. The summation of each energy contribution is done using a continuous joint probability density function of the length and orientation of the segments.