Probability models are developed for the failure of parallel brittle fibres embedded in a relatively soft plastic matrix. A loss of load-bearing occurs in the region surrounding a fibre break, resulting in a concentration of stress in neighbouring fibres. These stress concentrations cannot be measured directly, but by assuming them to be a chosen function of unknown parameters, the failure of the composite may be modelled. It is then shown how the stress concentration parameters may be estimated using the method of maximum likelihood. The technique is illustrated using experimental data for different materials, and in particular, it is shown how the stress concentration parameters vary with fibre spacing. The appearance of breaks along a fibre is, in nature, a point process. Load-sharing between two fibre processes will lead to a degree of nearly coincidental breaks. The degree to which 'coincidences' or 'matchings' occur in two independent point processes is examined. An unusually high degree of matching can be defined, and used to infer that processes are not independent. The exact analysis for a fibre-break process is intractable, but several approximate alternatives are studied, and compared with real and simulated data. The probability models for composite failure rely on assumptions about the underlying strength of the fibres. Principally, the 'weakest-link' property is assumed, frequently characterised by use of the Weibull distribution. A non-parametric test of this property is devised, and specially designed experiments show that weakest-link is apparently open to considerable doubt. It is shown that the existence of different causes of failure, all of which may not be present all of the time, give rise to some new types of failure model. It is demonstrated that these do not have the weakest-link property, even when based on the Weibull distribution, and that they are consistent with some experimental results.

The low abrasion resistance of wool fabrics compared with many man-made fibre fabrics is known to be a frequent cause of consumer dissatisfaction particularly in pure wool suiting fabrics. Accordingly this project was undertaken to attempt to improve the abrasion resistance in order to maintain the quality image associated with wool fabrics and improve their market competitiveness vis-ä-vis other fabrics. Although several workers have discussed the effects of particular finishes on specific fabrics, very little systematic investigation of the effects of chemical treatments on the abrasion resistance of wool fabrics has been carried out. In the current study the difference in abrasion rates of woven wool fabrics composed of different structures have been studied in relation to the abrasion resistance and other relevant physical properties. The work carried out in this thesis is divided into two parts. A review of the literature is followed by a description of the experimental work carried out. The review of the literature summarises current views on the general mechanisms and factors involved in abrasion processes for textile fabrics and the effects of selective finishing treatments on the abrasion resistance of wool fabrics. In addition details of the abrasion testing conditions used in this work for determining fabric abrasion resistance have been described. The' experimental work is concerned with the changes in wool fabric abrasion resistance produced by the following treatments: (i) Application of polymer shrink-resist finishes by padding and by exhaustion treatments, (ii) Treatment with organic solvents, (iii) Treatment with ethylene glycol at-1500C, (iv) Deamination and esterification, (v) High temperature steaming (130°C), (vi) Dyeing, (vii), Wet abrasion. Because of the great commercial importance of polymer shrink resist finishes for wool fabrics, the main objects of the experimental work were to establish the effects of a range of polymer shrink-resist finishes applied by conventional padding and exhaustion techniques on the abrasion resistance of wool fabrics and the mechanisms by which the abrasion resistance is improved.

This thesis reports the results of a study of problems associated with fabric sewing, such as seam pucker and sewing damage, in commercial garment manufacture. Part 1 continues previous work by the author on seam pucker in structurally jammed fabrics; in particular it has been shown that initial Young's modulus of a fabric is a measure of the ability of the fabric to accommodate compressive forces during sewing. This result provides an additional means of predicting the tendency of a fabric to exhibit seam pucker. The static mechanism of seam pucker proposed previously, based upon the relative magnitudes of bending stiffness of thread and fabric, has been revised by establishing that sewing machine dynamics and pucker are closely related. It has been shown that presser foot bouncing in particular induces pucker and that the sewing thread needs to be positively controlled during stitch formation. These results were verified by simple experimental methods, suggesting that modifications to the sewing machine are needed. Such modifications are beyond the scope of this work. Following the earlier static mechanism of seam pucker, it has been shown that seam pucker in fabrics is reduced significantly when the bending stiffness and extensibility of the sewing thread is reduced. In addition seam pucker can be eliminated by improving fabric stiffness locally along the seam area, by incorporating a stiffening material in the seam; this is based upon the technique of pucker elimination found in the author's previous work. In this study this technique is implemented with considerable success in other types of seams and commercially available stiffening materials have been selected. Part 2 investigates sewing damage to fabrics due to sewing needle penetration. Preliminary studies suggested the need for a reliable testing facility. This was made by instrumenting an industrial overlock sewing machine. The instrumentation was based on measuring the force which is exerted by the sewing needle when penetrating the fabric. The testing facility consists of the sewing machine with a strain gauged sewing needle and plate, and a shaft encoder for stitch marking, which with proper signal amplification and conditioning could be fed to a transient recorder and osciloscope for signal capturing and plotting. Investigations with fabrics revealed that the magnitude of the peak force of each stitch cycle can be related to the degree of sewing damage in the fabric. Based on these results the most important variables in sewing damage were fabric softening and its effective application during finishing, and sewing needle size. Studies of sewing damage under dynamic conditions have shown that sewing damage is a frictional problem between yarns in the fabric and between yarns and the metal of the sewing needle, foot, plate and feed dog. The size of the needle plate of the sewing machine seems to affect the degree of damage and fabric "flagging" during sewing damage has been experienced. Finally in the latter section of this study a prototype routine sewing damage tester has been developed and each stage of its development is described. This tester is based on an instrumented overlock sewing machine, which is interfaced with an IBM PC for computerised data capture and analysis in real time.

A mechanical method for reducing the spirality of single jersey tubular weft knitted fabrics is described. Initial attempts, using a false twisting device, did not prove successful. A later, successful method was developed, based on changes in yarn torque produced by a steaming and untwisting method. The new method is shown to be very effective in reducing spirality. Microscopic examination of changes in yarn structure, including characteristics of fibre migration have also been carried out.

The previous work on measurement of weaving resistance, i. e. the force needed to beat the weft into a fabric, is reviewed and the refinement of one method is described. That method is then used in a comprehensive set of experiments in which the tension applied to the warp and the balance and timing of the shed are all varied. A consistent pattern of influence of the settings on weaving resistance is established and illustrated in graphs. The main experiments relate to plain weave, but the weaving of 2/2 twill is covered in a rather less comprehensive way. The optimum settings are found to be different for the two weaves, and these differences are explained in terms of previous theoretical work. It is shown that the adoption of optimum settings permits the weaving of denser fabrics.

No description available.

Friction spinning is a relative newcomer to textile technology. It has generated great interest because of its potential for wide application of certain problems regarding the quality of yarn produced at high output rates can be solved. General acceptance of the process is hindered by uncertainty as to its capability of producing yarns of sufficient strength at speeds greater than 300 m/min. (NB: as a guide, maximum output rates of competitive technologies are no more than 150 m/min.) Friction spinning appears to have no intrinsic self-limit to its maximum output rate, unlike ring and rotor spinning which are limited by centrifugal effects leading to excessive yarn breakages. The process will therefore provide something of a quantum leap in output if acceptable yarn quality is achieved.