C.C. Cheng

A Continuum Mechanics Approach to Twisted Yarns

A new formulation of the mechanics of deformation of continuous filament textile yarns has been carried out which utilizes the concepts of classical continuum mechanics, particularly the stress tensor. The stresses acting on a fiber are divided into a tensile stress T acting along its axial direction, and compressive stresses Pn and Pb acting in the direction of the normal and binormal vectors of the equivalent space curve. The resulting expressions for the stress distribution in the yarn and the applied tensile force and torque are more general than those derived by earlier researchers.

Energy Losses within Sheared Fiber Assemblies

A theoretical treatment of fiber-to-fiber frictional character and internal energy losses within an oscillating fibrous mass is presented. Experimental evaluation of the theoretical result is given and discussed in terms of the correlations ob tained by extending over a wide range of the variables involved. A single measurable parameter obtained from the energy loss mechanism is derived which characterizes the processibiliy of the fibrous material.

The Detection of Cotton Fiber Convolutions by the Reflection of Light

A device which allows the azimuthal monitoring of reflected light is described. The results of measuring the azimuthal angles between maximum reflected light and one-half of maximum reflected light are given for nineteen varieties of cotton of the G. barbadense and G. hirsutum species. This angle is shown to be a function of the induced convolutions in cotton fibers. These measurements by a new technique are compared separately with x-ray and microscopic orientation results. Also, comparisons are made between zero-gage tenacity versus 40% x-ray angle and zero-gage tenacity versus 50% optical angle.

The Coefficient of Energy Dissipation from Sheared Fiber Assemblies

An experimental evaluation of a theoretical derivation pertaining to fiber-to-fiber character is presented. A portion of the relationship is separated and is then defined as the coefficient of energy dissipation. This coefficient is then evaluated for a number of cotton varieties as well as for a number of synthetic staple fibrous materials. Comparisons are made between the samples tested. The polyester specimens evaluated by this technique have also been studied by others using a different approach to what appears to be a similar problem. Comparisons have been made.

Scanning Electron Microscopy Study of the Deformation of Staple Yarns: Cotton, Polyester, and Cotton-Polyester Blends

The deformation of staple cotton, polyester, and cotton/polyester blend yarns has been studied in a small tensile device placed in a scanning electron microscope. The mechanics of failure of the different yarns are considered.

An Approach to Friction Effects in Twisted Yarns

A continuum-mechanical theory of continuous-filament yarn mechanics with interfilament friction has been developed. Specific consideration is given to models with shearing stresses as well as tension and compression of the filaments. The application to the static and dynamic deformation of yarns is considered.

Azimuthal Intensity Profiles of Scattered Light from the Surfaces of Convoluted Cotton Fibers

Azimuthal intensity profiles of scattered light from the surfaces of cotton fibers can be used to characterize the degree of fiber convolution. A theoretical treatment of the intensity distribution of scattered light from fiber surfaces is pre, sented and discussed in terms of surface geometry. The effect of instrumental design on the recorded profiles is discussed. Comparisons are made between the theoretical predictions and the experimental observations.

The Effect of Fiber Treatment on the Coefficient of Energy Dissipation

The coefficient of energy dissipation, which has previously been shown to characterize the surface properties of staple fibers, is examined for cottons extracted with alcohol, mercerized, washed in a water softener, baked, and partially coated with microscopic particulates. The effect of humidity on the coefficient of energy dissipation is observed and hysteresis effects are shown to occur as the humidity is cycled. Humidity effects are discussed in terms of previously published theory on interfiber frictional behavior.

Humidity and Heat Effects on the Coefficient of Energy Dissipation

Six varieties of cotton are heat treated at temperatures of 100°C, 140°C, and 180°C. Frictional parameters, via coeffi cicnts of energy dissipation, are measured on each of these and control samples (20°C) at a number of consecutive relative humidities (30%, 45%, 55%, 65%, 80%, 65%, 55%, 45%, and 30%). The results for all combinations are discussed. Comparisons between these findings and those of other investigators are made.

On the Torsion Constant of Cotton Fibers

The measurement of the torsion constant of cotton fibers is usually determined by the single-fiber method. The bundle method proves to be faster, and the determination of this physical property by the bundle method is analyzed and the experimental results are discussed.