Improved Methods of Determining Fibre Density

An account is given of an investigation of the effects of fibre type (rayon, acrylic fibre, wool, and cotton) and dimensions on the properties of needled fabrics, the test methods used being those described in a previous paper. Some fabrics show a stick-slip behaviour in extension; others deform smoothly. Rayon webs consolidate more easily on needling than Courtelle or wool webs. Longer fibres give higher fabric strengths. Finer fibres also give higher strength, unless fibre damage occurs. The influence of fibre friction is discussed.     

22—A THEORETICAL AND EXPERIMENTAL INVESTIGATION OF THE CREASE RECOVERY OF PLAIN-WEAVE FABRICS WOVEN FROM STAPLE YARNS

The retained angle at a crease is considered to be made up of two components: inelastic and frictional. A theoretical scheme has been developed that enables the inelastic component to be calculated from the appropriate fibre, yarn and fabric data and the calculations are illustrated for three fabrics.

An experimental investigation of the crease-recovery behaviour of these fabrics, in conjunction with the calculations described above, has established a method of deducing the frictional component from the low-curvature bending-recovery behaviour of a fabric, and it is thus possible to make an estimate of the fabric crease-recovery angle. The calculation has been carried out for a range of fabrics woven from eighteen fibre types, each in four different cover factors, and the results are shown to agree reasonably well with the measured crease-recovery angles for the same fabrics. The experimental results are discussed and some interesting relationships are pointed out; in particular it is shown that fabrics must be well relaxed if the full potential of a high-recovery fibre is to be realized.     

24—THE BENDING BEHAVIOUR OF PLAIN-WEAVE FABRICS WOVEN FROM SPUN YARNS

The bending behaviour of square plain-weave fabrics spun and woven from nineteen different fibres, each in a range of cover factors, has been studied. It is shown how this behaviour is determined by the mechanical properties of the fibre and the frictional and geometrical restraints within and between yams in the fabric. The effects on these restraints of cover factor and of relaxation in wet finishing and in heat-setting are examined. Factors affecting cloth stiffness are summarized, and it is shown that two quantities, an elastic component and a frictional component, are required to specify the bending behaviour with reasonable completeness.     

27—THE BENDING AND CREASING OF MULTICOMPONENT VISCOELASTIC FIBRE ASSEMBLIES. PART I: GENERAL CONSIDERATION OF THE PROBLEM

The problems involved in making a mechanical analysis of bending deformations in textile fabrics are discussed. It is suggested that progress can be made by making simplifying assumptions concerning the geometry of fabric structure and deformation and using energy considerations to calculate forces and moments. Certain simple examples are given of the usefulness of this approach. A foundation is laid for the construction of a computer model that will, it is hoped, simulate the viscoelastic bending and creasing behaviour of textile fabrics from a knowledge of the bending and torsional viscoelastic properties of the constituent fibre(s) and their relative geometrical arrangement.     

14—A STUDY OF NEEDLED FABRICS. PART IV: THE EFFECTS OF STRETCH,SHRINKAGE, AND REINFORCEMENT

Changes in fabric dimensions (length, width, and thickness) at the centre of a strip were measured both in continuous extension and in cycling tests. Values of Poisson's ratio, elastic recovery, and fabric density were calculated. The effect of pre-stretch on fabric properties was studied. The effects of shrinkage were investigated by examining the properties of fabrics produced from rayon blended with varying amounts of a polyester fibre that shrank in boiling water. Shrinkage caused considerable consolidation of fabrics. The effects of combining a woven base with a needled structure were studied on three laboratory-produced fabrics and several commercial samples.     

28—SOME FACTORS INFLUENCING PUCKERING AND COCKLING IN FULLY FASHIONED GARMENTS

A simple technique for the planning of rib cuffs and welts for fully fashioned garments that is based on the classical knitting geometry of plain and 1 × 1 rib fabrics is described. The effects of cover factor and some common loop ratios at the join of 1 × 1 rib and plain fabrics on puckering at the knitted join and the effects of cover factor and some yam characteristics on cockling in plain-knitted fabrics are given.     

19—A STUDY OF NEEDLED FABRICS. PART VI: THE MEASUREMENT OF PUNCHING FORCE DURING NEEDLING

An account is given of an investigation in which a small needle board was fitted to the compression cage of an Instron Tensile Tester and used to measure the forces developed during the penetration of a web by needles. The punching speeds were much lower than those in a needling machine. The effects of web weight, type of fibre, fibre length and fineness, density, a reinforcing base fabric, and punching speed were studied.     

21—THE MEASUREMENT OF FABRIC DRAPE

It is shown how the method of measuring fabric drape by supporting a circular specimen of fabric between smaller horizontal circular plates has been modified to allow a more sensitive test to be made on very stiff and very limp fabrics. The use of diverging light instead of parallel light is described, and the correction of the results for this change is calculated. A method of determining the drape coefficient by a paper-weighing method is also described.     

18—THE ABRASION-RESISTANCE OF SOME WOVEN FABRICS AS DETERMINED BY THE ACCELEROTOR ABRASION TESTER

The use of an Accelerotor abrasion tester is discussed, and the abrasion-resistance of several plain-weave fabrics is shown to depend on the type of fibre. The materials are ranked in order of decreasing resistance to abrasion with carborundum, rubber, metal, and plastics abradants. Polyamide fibres have outstanding resistance and cellulose-ester and regenerated protein fibres poor resistance to abrasion. The order of resistance of other synthetic-polymer fibres, regenerated cellulosic fibres, and natural fibres is shown to alter slightly according to the nature of the abradant, the linear density of the fibre, and the sett of the fabric. The results are in general agreement with published data, but the resistance of polypropylene-fibre fabrics is lower than it was expected to be.

Microscopical examination of detritus confirmed that this consisted of small segments of complete fibre, which indicated that abrasion occurs by fibre breakage. A useful correlation is established between the specific strength and initial modulus of a fibre, or the energy of rupture of mechanically conditioned fibres, and the abrasion-resistance of a fabric.     

30—THE EFFECT OF VARIABILITY OF FIBRE DIAMETER ON WORSTED PROCESSING: PART I. THE USE OF COMPARISON SAMPLES FROM A SINGLE MERINO FLOCK

Two greasy-wool bulks were made up from sound fleeces selected from a single medium-merino flock so that their mean diameters, mean staple lengths, and mean crimp frequencies would be the same or similar, but the coefficients of variation of diameter (V _d) would be different. The tops made from these bulks showed closely similar mean fibre diameters (20·6 and 20·8 (μm), lengths, and length variabilities, with the V _d values 18·3% (L) and 21·4% (H). In conventional Bradford spinning, L was slightly favoured over H at the spinning limit, but the differences in ends-down per 100 spindle-hours at commercial counts were negligible. Yarn properties, such as tensile strength and elongation at break, and yarn evenness did not disclose differences of any consequence. Fabrics made from 25-tex yarns gave closely similar properties. Ambler Superdraft spinning supported these conclusions.

The difference of 3% in V _d values did not indicate significant worsted-manufacturing differences between the tops. Since these tops were made from single-quality sources, the V _d values are low compared with the range of values for European tops of the same diameter, the majority of which would occur in the 20–26% V _d range.