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.     

26—THE WRINKLING OF WOOL WORSTED FABRICS. PART II: BENDING SET IN SINGLE FIBRES AND FABRIC AND THE EFFECT OF AGEING

An account is given of an investigation in which the recovery from bending of isolated wool fibres subjected to strains similar to those found in a wool fabric during bending in the multiple-pleat tester was measured. Fabric recovery and fibre recovery differ by a small amount that is probably produced by friction hindering relative movement. The improvement of fabric recovery with ageing is shown to be a single-fibre property, the friction being apparently unchanged.     

36—THE AGEING OF WOOL. PART II: THE AGEING OF DISORGANIZED FIBRES

Experiments are described in which the stress-relaxation and recovery behaviour in bending is determined during ageing for wool fibres previously disorganized by a treatment in boiling water and is shown to be generalized linearly viscoelastic. This behaviour is also shown to parallel that of the stress-relaxation and ageing behaviour of native fibres in torsion, which is known to reflect the behaviour of the matrix component of structure. The results are shown to be consistent with a hypothesis proposed by Rigby et al. It is also demonstrated that the microfibrillar regions of the fibre contribute a constant spring-like component to the modulus, which does not stress-relax or age but is destroyed when fibres are disorganized by a treatment in boiling water. It seems certain that the major mechanical effects observed during ageing result directly from processes occurring in the matrix.     

25—THE WRINKLING OF WOOL WORSTED FABRICS. PART I: FIBRE AND YARN DEFORMATION IN BENDING

Experiments are described in which the extensional, bending, and twisting strains of seven fibres were measured in a wool worsted fabric deformed in a multiple-pleat tester. The only significant strain appeared to be the bending strain.     

74—A STUDY OF OPEN-END SPINNING BY CIRCUMFERENTIAL ASSEMBLY,WITH ESPECIAL REFERENCE TO THE SPINNING OF MODIFIED RAYON. PART II: FIBRE ASSEMBLY

The process of yarn formation in the BD 200 open-end-spinning machine is investigated, and the optimum conditions when Vincel modified viscose rayon fibre is used are determined. The processes of fibre assembly and yarn formation within the spinning chamber are particularly considered.     

28—THE BENDING BEHAVIOUR OF A HELICAL FILAMENT PART I: THE RIGIDITY OF THE HELIX

The large-scale bending of a helical filament is considered. It is shown that, in many cases likely to be of interest in textile applications, the bending rigidity of the helix calculated from small-deflexion theory provides a good approximation to the large-deflexion case. The cross-section of the deformed helix and the position of the neutral axis are also discussed.     

70—THE MECHANICS OF SELF-PLYING STRUCTURES. PART II: MULTIFILAMENT STRANDS

Analyses of the mechanics of self-plying structures are presented for multi-filament component strands, and an account is given of the experimental verification of theoretical predictions, made by means of the use of nylon multifilament model yarns.     

33—HIGH-INTENSITY DRYING OF TEXTILE FIBRES. PART III: THE EFFECT ON THE RATE OF DRYING OF NON-UNIFORMITIES IN FIBRE AND MOISTURE DISTRIBUTION WITHIN A BED OF FIBRES OR YARNS

Experiments are reported that show that, during the drying of loose fibrous assemblies, there is a preferential diversion of the air stream through wetter areas of the bed. It is shown theoretically that this could be due to differences in the cooling effect on the hot drying air of fibres containing varying amounts of moisture.

It is also shown that the rate of drying can be increased considerably by accentuating this phenomenon when the bed is supported on the downstream side by a perforated plate with a restricted free area of holes.

In addition, the use of such a plate reduces the unproductive channelling of the drying air through the less dense areas and in the extreme cases through ‘holes’ in the bed (e.g., in the drying of hanks of yarn) and results in a dramatic increase in the rate of drying.     

3—A FIBRE MORPHOMETER. PART I: THE THEORY AND OPTICS

Fibres are generally neither circular nor uniform, but their exact morphology is of great technical importance. Although many existing systems are available for the estimation of diameter for various purposes, none conveniently allows for routine analysis of all the parameters of fibre shape. This paper describes a simple optical system and a set of mathematical formulae to allow such analysis that have been developed for ellipses. It is indicated how extension to other shapes is possible. A brief treatment of theoretical aspects of microprojection measurement of elliptical fibres is also presented.     

53—HIGH-INTENSITY DRYING OF TEXTILE FIBRES. PART IV: PREDICTION OF THE DRYING TIME FOR TEXTILE ASSEMBLIES

The physics of drying a bed of loose textile fibres is discussed in relation to methods of predicting the drying times. An empirical method developed by other workers for predicting the drying times for flax stalks is reviewed and its applicability to loose fibres examined theoretically. It is concluded that, although the method is strictly applicable to the drying of non-absorbent fibres, it is also relevant to the drying of wool under industrial conditions. The experiments reported confirmed this expected deduction. A few observations covering the intended range of application should make it possible to predict the drying times for any combination of variables within the range.     

61—AN INVESTIGATION OF THE TAPER OF COTTON FIBRES. PART II: THE LENGTHWISE VARIATION OF MOLECULAR ORIENTATION IN COTTON FIBRES

An investigation is described in which the variation in the orientation of the chain molecules and the crystallites along the length of the cotton fibre was studied by employing optical and X-ray techniques. Three distinct regions, namely, the root, middle, and tip, of the fibres belonging to the modal-length group of the cottons were scanned. Birefringence was determined by the Beckeline method and root-tip-aligned bundles mounted on special clamps were used for the X-ray studies. Cottons of widely varying fibre properties and belonging to different botanical species were investigated.

The data revealed that the birefringence of the fibres increased significantly from root to tip through the middle. The X-ray crystallite orientation at the root was also found to be significantly lower than that in the other regions. These observations lead to the inference that the molecular chains become progressively better aligned as one proceeds from the root to the tip of a fibre. Intra-fibre variation and the discrepancies between the optical and X-ray measurements are discussed in terms of the fibre profile.     

14—AN INVESTIGATION OF THE TAPER OF COTTON FIBRES. PART IV: THE DIFFERENTIAL BEHAVIOUR OF FIBRE ENDS DURING THE PROCESSING OF COTTON

This paper reports the results obtained in a study made on five cottons to assess the differential response of the root and tip parts of the fibre in the formation of hooks in card sliver and to determine its effect on the hairiness and migratory behaviour in the yarn.

Experiments employing tracer techniques show that the tip ends are more prone to the formation of hooks than the root ends in card sliver and that they have a greater hook extent. The root ends constitute a higher proportion of protruding hairs, with longer protruding fibre extents. The root part tends to migrate to the periphery, with a higher migration intensity, and the tip part to the core of the yarn.     

13—AN INVESTIGATION OF THE TAPER OF COTTON FIBRES. PART III: VARIATION IN THE MECHANICAL PROPERTIES OF A COTTON FIBRE ALONG ITS LENGTH

The pattern of distribution of the mechanical properties and structural reversals along the fibre and their dependence on the fibre profile are reported in this paper. Experiments on twelve cottons showed that both the fibre tenacity and the percentage elongation increased steadily from the root part to the middle region and then decreased to a minimum value at the tip part of the fibre. The decrease in tenacity from the middle to the tip part of the fibre was found to be influenced by the fibre profile. The structural reversals increased from the root to the tip through the middle, and the maximum variation was observed in fibres having the highest uniformity in the cross-sectional shape of the fibre along its length. The variation in the structural reversals is shown to be a factor responsible for the observed distribution of tenacity along the fibre.     

29—THE BENDING BEHAVIOUR OF A HELICAL FILAMENT PART II: CURVATURE,TWIST, AND STRAIN ENERGY

The variation of curvature and twist along a bent helical filament is discussed. Also considered is the strain energy in the deformed helix.     

71—HIGH-INTENSITY DRYING OF TEXTILE FIBRES. PART II: THE PRESSURE DROP DUE TO THE FLOW OF HOT AIR THROUGH BEDS OF DRYING FIBRES

An equation is developed for predicting the pressure drop required to maintain a given air-flow in assemblies of wet loose fibres during the intial stages of drying. The experimental testing of the equation is described. It reflects the influence of the fibre diameter, the compression of the bed, the weight of fibres per unit area of the bed, and the velocity and density of the air used for drying.

It was observed that the resistance of a given bed to flow increases as the regain in the bed decreases. The proposed equation therefore applies only to the initial stages of drying.     

31—THE EFFECT OF VARIABILITY OF FIBRE DIAMETER ON WORSTED PROCESSING. PART II. THE USE OF COMPARISON SAMPLES OF COMMERCIAL TOPS AND THEIR BLENDS

Changes in the coefficient of variation of fibre diameter (V _d ) were made by blending top qualities (a) 70s and 56s, and (b) 60s and 56s, and comparing these with a 58s. In this way, a range of values of V _d from 21.4 to 24.9% was obtained over three top samples whose mean fibre diameters and fibre lengths were closely similar. These tops were worsted-spun to determine their performance at the spinning limit and other yarn counts and to measure the yarn properties. The three samples did not give any important differences in chemical composition or in spinning limit, but did show a trend to significant differences in yarn breaking strength and elongation, the lower-V _d sample being favoured. Over this range of values of V _d at mean diameters of 25–26 μm, although there are hints of slight differences in spinning and in the product, the trend is not important. The range of V _d values for European tops of mean fibre diameter 25.3 μm appears to lie between 22 and 28%. The Australian tops investigated gave V _d values over the lower half of this range.     

57—HIGH-INTENSITY DRYING OF TEXTILE FIBRES. PART I: THE NATURE OF THE FLOW OF AIR THROUGH BEDS OF DRYING FIBRES

A theoretical analysis of the nature of non-isothermal flow in beds of drying loose-fibre assemblies indicates that the bed structure is sufficiently open for the air velocities normally encountered in industrial dryers to result in non-laminar flow. Experiments are reported that support this deduction and indicate that, under industrial conditions, the viscosity effects on the resistance of the beds to flow are negligible and the pressure drop due to flow is practically proportional to the square of the air velocity.     

42—THE RAPID MEASUREMENT OF THE TENSILE PROPERTIES OF FIBRE BUNDLES PART II: EXAMPLES OF EXPERIMENTAL RESULTS

An account is given of the use of the bundle tester described in Part I of this series to determine the breaking force, work of rupture, and elongation at break of various textile specimens. Typical results (which include tests on wool staples and semi-processed materials) are reported.     

49—SOME ASPECTS OF WORSTED-YARN STRUCTURE. PART II: THE MECHANICAL STATE OF SINGLE FIBRES LEAVING THE DRAFTING ZONE

An investigation is described in which a novel method of constraining drafted material between transparent adhesive tapes was used to show that, whereas the main single-fibre strain-inducing parameter is the insertion of twist into a yarn, a significant amount of this strain occurs as a result of the drafting process. The differences in behaviour during drafting of the leading and trailing ends of fibres are also demonstrated.     

25—A STUDY OF THE STRENGTH OF WRAPPED YARNS PART II: COMPUTATION AND EXPERIMENTAL

By substituting appropriate values into a theoretical model of wrap-spun yarns, it is possible to predict their tensile behavior. The predicted values are compared with experimental data, and reasonable agreement is shown to exist except at high twist levels. An explanation is given for the increasing deviation between predicted and experimental values as the twist is increased.