END BREAKAGE IN ROTOR SPINNING: EFFECT OF DIFFERENT VARIABLES ON COTTON YARN END BREAKAGE
The end breakage in rotor spinning not only reduces the running efficiency of the process, but also deteriorates the quality of the yarn in terms of presence of piecing slubs. A new system has been proposed to classify the end breaks in rotor spinning broadly into seven groups, depending on the configuration of broken ends. By examining the broken end, the probable causes of breakage can be predicted and necessary preventive action can be taken. The rate of end breakage and the proportion of different types of breakages vary with different process variables like yarn count, rotor speed, opening roller speed and residual trash content in draw frame sliver.
MECHANICS AND ANALYSIS OF FABRIC COMPOSITES AND STRUCTURES
This paper is devoted to the mechanics, modelling and analysis of fabric-reinforced composites and structural components. A theoretical and experimental characterisation of elastic properties of the textile composites is considered. Typical stress-strain diagrams for fibreglass fabric composites and composites reinforced with knitted fabrics loaded in tension at different angles are presented. The special case of the three-dimensional reinforcement structure of composite material, composed of spatially-oriented fabric layers is discussed and corresponding models considered. Manufacturing technology for such structures includes a three-dimensional lay-up process in which the specially designed fabric patterns are placed onto the mould or mandrel. The implementation of the material model is illustrated with results of the stress-strain analysis of thin-walled spatially reinforced structural components.
MODELLING AND SIMULATION OF THE MECHANICAL BEHAVIOUR OF WEFT-KNITTED FABRICS FOR TECHNICAL APPLICATIONS Part IV: 3D FEA model with a mesh of tetrahedric elements
This paper is in four parts. The first is related to general considerations and experimental analyses, and each of the others is related to different approaches to the theoretical analyses of the mechanical behaviour of weft-knitted fabrics and weft-knitted reinforced composites made of glass fibre. The objective is to find ways of improving the mechanical properties and simulating the mechanical behaviour of knitted fabrics and knitted reinforced composites so that the engineering design of such materials and structures may be improved.
In Part IV the technologies for weft-knitted 3D complex shape preform development are surveyed and a third model is presented. This a 3D model based on FEA (finite element analyses). A solid representation of a 2D yarn is built up, and an MES (mechanical event simulation) is applied to obtain a 3D-shaped loop. The final knitted fabric geometry is obtained by interacting this loop with the adjacent loops, according to the dimensional properties of the knitted fabrics and using an MES. Finally, the geometry of the reinforcement inside the composite is built up, and the composite material is divided into small tetrahedric elements to obtain a mesh of finite tetrahedric elements (FEA). The average values of the mechanical properties are obtained with FEA and compared with the experimental ones.
INFLUENCE OF LOOP POSITION IN WARP-KNITTED PLAIN STITCHES ON STRUCTURAL PROPERTIES OF KNITTED FABRICS
This paper presents the structure of a new group of warp-knitted interlock stitches. The difference between them and generally-known warp-knitted stitches is emphasised. We describe an alternative method of manufacturing knitted fabrics with the above-mentioned stitchesusing a warp-knitting machine equipped with a tuck pressure. This paper describes an estimation of the structural properties of the warp-knitted fabrics manufactured by means of interlock and traditional stitches.
DESIGN OF NONWOVEN SCAFFOLD STRUCTURES FOR TISSUE ENGINEERING OF THE ANTERIOR CRUCIATE LIGAMENT
This work is concerned with improving the design of textile scaffolds used to tissue-engineer anterior cruciate ligaments. Two important design criteria of a scaffold are internal structure and cell-fibre compatibility. This paper considers both of these criteria, providing a review of scaffold design and structural parameters, followed by experiments on the biocompatibility of various generic fibres.
In this paper, the influence of surface area to volume ratio and polymer morphology on cell-surface interactions is discussed, together with a consideration of the effect of pore-size and scaffold porosity on cell proliferation, migration and nutrient supply. Another structural factor discussed is the role of fibre orientation as a means of guiding and organising new tissue growth. It is possible to manipulate these scaffold parameters to produce a scaffold of optimal structural design for the tissue engineering of the anterior cruciate ligament.
A review of current scaffold types classified according to manufacturing method is presented. These manufacturing methods include solvent casting/particulate leaching, three-dimensional printing and fibre bonding. Scaffolds in fibrous form include woven, knitted, braided, embroidered and more recently nonwoven.
Biocompatibility tests performed by the authors study the reaction of fibroblast cells to the surface of different generic fibre types; including para-aramid, polyester, polypropylene, polyglycolic acid and viscose rayon. The results of these tests are discussed in relation to cell attachment and fibre morphology.
IONIC CROSSLINKING OF COTTON
Cellulose crosslinking is a very important textile chemical process, and is the basis for a vast array of durable press- and crease-resistant finished textile products. N-methylol crosslinkers containing formaldehyde give fabrics desirable properties of mechanical stability (e.g. crease resistance, anti-curl, shrinkage resistance, durable press), but also impart strength loss and the potential to release formaldehyde, a known human carcinogen. Other systems, e.g. polycarboxylic acids, have been tested with varying degrees of success. We have developed methods of forming ionic crosslinks that provide outstanding crease-angle recovery performance, as well as complete strength retention in treated goods, without the potential for releasing any low-molecular weight reactive materials, such as formaldehyde. Our work is based on reactions of cellulose with materials that impart an ionic character to the cellulose, e.g. chloroacetic acid for negative charges or 3-chloro-2-hydroxypropyl trimethyl ammonium chloride for positive charges. These reactions produce ionic celluloses that can then sorb a polyionic material of opposite charge to form crosslinks. Cellulose treated with cationized chitosan after carboxymethylation showed significant increases in crease recovery angles without strength loss.
THE EFFECTS OF WASHING CONDITIONS ON SOIL REMOVAL IN DOMESTIC LAUNDERING PROCESSES
In the domestic laundering process, relatively high wash temperatures and long wash times have traditionally been used for optimum soil removal. The use of lower wash temperatures could result in a substantial reduction in the amount of energy used in laundering. The purpose of this study was to determine soil removal from cotton, polyester, polyester/cotton, wool and wool/polyester fabrics at a range of wash temperatures, wash times, pre-wash times and liquor ratios. The samples were soiled with sebum, coke, instant coffee, sour cherry juice and meat sauce. Soil removal was determined by the differences between remission values of fabrics before and after washing. Optimum temperature and times for soil removal was estimated for all soils and fabrics.