R. Postle

Weibull analysis of the tensile behavior of fibers with geometrical irregularities

This paper further develops the conventional Weibull/weakest-link model by incorporating the within-fiber diameter variation. This is necessary for fibers with considerable geometrical irregularities, such as the wool and other animal fibers. The strength of wool fibers has been verified to follow this modified Weibull/weakest-link distribution. In addition, the modified Weibull model can predict the gauge length effect more accurately than the conventional model.

Textile and apparel supply chain management in Hong Kong

Purpose – This paper aims to review the concept of supply chain management. The typical problems facing with textile and apparel supply chain are short product cycle for fashion articles, long production lead‐time and forecasting errors for fashion items. The Hong Kong textile and apparel supply chain faces additional problems of distance from customers in the US and European markets, long production lead‐times and minimum batch sizes for production, and, recently, elimination of quota restriction in the US market, all of which force them to improve efficiency and enhance competitiveness through supply chain management. Seeks also to provide a selective bibliography for industrial practitioners with sources which can help them develop their supply chain strategies for the fashion market in Hong Kong.Design/methodology/approach – A range of recent published (1993‐2005) works, which aim to provide practical advice are critiqued to aid the individual practitioner to manage its supply chain strategies in Hong...

39—AN ENERGY ANALYSIS OF WOVEN-FABRIC MECHANICS BY MEANS OF OPTIMAL-CONTROL THEORY PART I: TENSILE PROPERTIES

The general energy analysis of fabric mechanics by means of optimal control presented in a previous publication is applied to the woven-fabric structure for deformations whereby the yarns remain in the same plane. The three-dimensional equations of the general theory are reduced to two-dimensional form, the boundary conditions are evaluated for the plain-weave fabric in biaxial tension, and an important mechanism of woven-fabric extension, which was not included in the general analysis, namely, the possibility of yarn extension, is introduced into the theory. The fabric load–extension curves and yarn-decrimping curves for the plain-weave construction are computed for a realistic range of input parameters: the yarn extension rigidity, weave crimp, degree of set, lateral yarn compression, and ratio of the curvilinear length of yarn in the warp direction to that in the weft direction of the fabric. The computed results are discussed in terms of the following dimensionless parameters: the applied tension per ...

A Theoretical Analysis of the Plain-Knitted Structure

A theoretical analysis was made of the relaxed plain-knitted structure. The analysis differs from previous ones in that no arbitrary geometrical loop shape is assumed and no empirical methods are used. The loop configuration is de rived from consideration of the reaction forces and couples acting within the structure, their magnitude being determined by the yarn displacement necessary for loop interlocking. A minimum-energy structure is shown to exist; this structure is fairly independent of fabric tightness and yarn properties. The actual energy minimum is fairly shallow, so that in practice some difficulty could be expected in obtaining a perfectly relaxed fabric; this would lead to a corresponding spread in experimental values of plain-knitted fabric shape and dimensions. The numerical values of fabric dimensions obtained from the analysis show good agreement with the experimental data reported by other workers.

Measuring and Interpreting Low-Stress Fabric Mechanical and Surface Properties Part I: Precision of Measurement

The results of an extensive study are reported involving the variability of measuring low-stress fabric mechanical and surface properties for a range of 30 wool and wool blend suiting fabrics. Seven sets of KESF instruments were used for the interlaboratory tests in Australia, Japan, Germany, the United Kingdom, New Zealand, and the Peo ples Republic of China. Values are given for the repeatability and reproducibility of 37 parameters and ratios characterizing the elastic and inelastic components of fabric deformation in tension, shear, bending, and lateral compression, as well as fabric surface behavior, that is, surface topography and friction. Measurement precision is also specified in terms of the maximum error for these parameters. The variance of the measurements is quoted in terms of its within-laboratory, between-laboratory, and specimen-laboratory interaction components. Recommendations are made for both the in-house product and process development situations (within laboratory) and for specifications for commercial transactions (between laboratory) as to the number of tests that should be performed in order to achieve a given level of precision. Though varying numbers of tests are recommended for some parameters, a general rule of three tests per sample may be taken as a guide.

An Analysis of the Bending and Shear Properties of Woven, Double-Knitted, and Warp-Knitted Outerwear Fabrics:

Mechanical properties of a wide range of commercially-produced outerwear fabrics have been analyzed in terms of the elastic and frictional resistance to bending and shear deformations. The fabrics tested include wool and wool-synthetic blend woven fabrics, wool and textured polyester double-knits, and synthetic warp-knits; some plain single jersey knitted fabrics are also included for comparison purposes Features of the bending and shear deformation and recovery curves such as their shape, asymmetry, linearity, and degree of hysteresis are discussed for each. Finishing has an enormous effect on the bending properties of all the woven fabrics an on the knitted synthetic fabrics, although the effect is less (although still significant) for knitted wool fabrics; the frictional resistance to deformation (in both bending and shear) is always much more critically affected by finishing than is the elastic rigidity of the fabric. Statistical correlations between the elastic and frictional parameters of deformation are explained in physical terms related to the basic fabric construction. Fabric bending properties are shown to depend largely on fabric thickness and other constructional variables, but shear properties show much less systematic variation with such parameters and are largely determined by the type of fabric construction itself. The effect of finishing is also much less for shear than for bending, particularly in the case of knitted structures. The frictional resistance to bending and shear deformations may be used to construct a two-dimensional fabric chart in which each group of fabrics falls into a separate area according to fabric structure and fiber type. This chart may be related to such fabric characteristics as tailorability, drape, and handle.

Bending and Recovery Properties of Wool Plain-Knitted Fabrics

In this paper an experimental study is reported of the pure bending and recovering properties of wool plain-knitted fabrics for bending in the two principal directions of the fabric. The mechanisms of fabric bending were found to be relatively complex and were studied from both a geometrical and rheological point of view. Several parameters were required to specify completely the fabric hysteresis in bending. The variation of these parameters with fabric tightness factor was noted and the effects of fabric relaxation studied. A method for measuring the curling couple of an unrelaxed knitted fabric is presented.,

23—A THEORETICAL ANALYSIS OF THE TENSILE PROPERTIES OF PLAIN-KNITTED FABRICS. PART I: THE LOAD-EXTENSION CURVE FOR FABRIC EXTENSION PARALLEL TO THE COURSES

An investigation is described in which, by means of a two-dimensional model of the plain-knitted structure, load-extension curves for extension in the course direction were calculated theoretically. It was assumed initially that the only mechanism of fabric extension was elastic deformation of the loop shape. Account was taken of setting of the yarns into the relaxed-loop shape, but this was found not to have any significant effect on the theoretical load–extension curves. It was found that the intial portions of these curves were almost linear but that the slope could be greatly affected by the occurrence of lateral yarn compression. When yarn compression was taken into account, good agreement was obtained with experimental results for a nylon-monofilament fabric and a series of wool plain-knitted fabrics.

34—AN ENERGY ANALYSIS OF THE MECHANICS OF WEFT-KNITTED FABRICS BY MEANS OF OPTIMAL-CONTROL THEORY PART I: THE NATURE OF LOOP-INTERLOCKING IN THE PLAIN-KNITTED STRUCTURE

A general energy analysis formulated for the study of fabric mechanics is applied to the biaxial-deformation properties of the plain weft-knitted structure by assuming quarter-loop symmetry. The basic equations of equilibrium and the boundary conditions for plain-knitted fabrics are derived without assuming any detailed pre-conditions relating to the nature of loop-interlocking. Typical equilibrium solutions for the plain-knitted structure under zero (or very low) tension are presented in this paper in the form of loop shapes and curvatures, continuously distributed forces acting between interlacing yarns, loop-jamming forces, and profiles for the inter-yarn distance within the structure. It is shown that the nature of yarn contact between interlocking loops varies greatly according to such factors as the degree of lateral yarn compressibility and the level and direction of tension applied to the fabric. The dynamic nature of loop-interlocking is discussed in relation to previously published models of the...

Evaluating Wool Shirt Comfort with Wear Trials and the Forearm Test

The comfort of light-weight woven fabrics in the form of next-to-skin clothing is investigated by wear trials and the forearm test. The wear trial in neutral environmental conditions shows that light-weight wool and wool blend fabrics are generally less comfortable than the summer polyester, cotton poplin, and polyester/cotton, fabrics tested in this study. In terms of comfort, the main shortcoming of these light-weight wool fabrics is prickle. When the environmental temperature is high, especially when the body is sweating, the comfort of wool and wool blend fabrics is greatly reduced due to signifi cantly increased prickle. The forearm test in neutral environmental conditions shows that fabric-evoked prickle decreases with an increasing wool quality number, i.e., as the wool becomes finer. For light-weight wool and wool blend woven fabrics proddced from 70s quality and coarser wools, there is the potential problem of prickle when used as next-to-skin clothing materials.