Virtual textiles

Verpoest I, Lomov SV. Virtual textile composites software Wisetex integration with micro-mechanical, permeability and structural analysis. Compos Sci Technol 2005 65(15-16) 2563-74. 

The micro-scale study focuses on the flow around the textile fibres. For this, one needs a computational representation of the fabric microstructure (sometimes referred to as a virtual textile). An example is schematically presented in Fig. 11.3 (left). Here, the shape, diameter and distribution of the textile fibres is based on the average values observed in a microscopic image of an actual CBRN protective textile. The inflow boundary conditions (velocity magnitude and direction) can be obtained from experimental data or from meso-scale RANS and DNS simulations. 

For the micro-scale simulations of flow around textile fibers, Sobera et al. [8] simulated a 3-dimensional flow domain, with a virtual textile plane halfway and parallel to the inflow and outflow boundary of the domain. The inflow boundary conditions (laminarized flow in the vicinity of the textile) are obtained from the meso-scale DNS simulations. Periodic boundary conditions are applied to the edges of the virtual textile. Considering the textile as a 2-dimensional array of cylinders, at a mutual half distance, porosity is given by ... 

Chemicals are ubiquitous as air, carbohydrates, enzymes, lipids, minerals, proteins, vitamins, water, and wood. Naturally occurring chemicals are supplemented by man-made substances. There are about 70000 chemicals in use with another 500-1000 added each year. Their properties have been harnessed to enhance the quality of life, e.g. cosmetics, detergents, energy fuels, explosives, fertilizers, foods and drinks, glass, metals, paints, paper, pesticides, pharmaceuticals, plastics, rubber, solvents, textiles thus chemicals are found in virtually all workplaces. Besides the benefits, chemicals also pose dangers to man and the environment. For example ... 

Virtually all of the nitrobenzene made is converted to aniline. The most important use of aniline is for the preparation of 4,4 -diaminodiphenyl methane (commonly called methylenedianiline or MDA), an intermediate to one of the main ingredients used to make polyurethane foams and rubber. Aniline is also used to make other rubber chemicals, textile fiber intermediates, dyes, and pharmaceuticals. 

Virtually all commercial textile dyeing and printing processes take place by the application of a solution or a dispersion of the dyes to the textile material followed by some type of fixation process. The dye solution or dispersion is almost always in an aqueous medium. A major objective of the fixation step is normally to ensure that the coloured textile exhibits satisfactory fastness to subsequent treatment in aqueous wash liquors. In view of the overriding importance of water as a transfer medium in dyeing and printing it seems reasonable to begin with a discussion of the properties of dyes in solution and in dispersion. 

Polyethylene terephthalate melts at round 265°C and is resistant to heat and moisture. It remains virtually unattached by most of the chemicals. It is extensively used to make textile fibres. It has good mechanical strength up to 175°C. Garments prepared from its fibres resist the formation of wrinkless. PETP can also be... 

Coal tar dyes first came on the market in the late 1850 s, and within a few years had virtually replaced natural dyestuffs in the textile trade. Almost from the first, these same dyes... 

The standard conditions are (a) 23°C and 50% relative humidity, and (b) 27°C and 65% humidity, with the latter condition intended for use in tropical countries. Where control of temperature only is required, this is either 23°C or 27°C, and a further atmosphere where neither temperature nor humidity need be controlled is defined as prevailing ambient temperature and humidity. A note drawing attention to the atmosphere 20°C and 65% relative humidity which was used for textiles is no longer included. The normal tolerances are 2°C on temperature and 10% on relative humidity however, provision is made for closer tolerances, if required, of 1 °C and 5% relative humidity. This is a welcome change from previous conditions when the standard humidity tolerances of 5% and 2% were unreasonable in that 2% is virtually impossible to achieve and 5% debatable. It should be noted that 20°C is the usual temperature for calibration laboratories although in most cases the three degree difference will not have a significant effect. 

The adhesion of cord, textile or metal, to rubber is a specialised measurement in that virtually all interest centres on tyres and to some extent belting. Most static tests consist essentially of measuring the force to pull a cord out of a block of rubber into which it has been vulcanised and it is apparent that the result is critically dependent on the efficiency with which the test piece was moulded. The measured force is also dependent on the amount that the rubber deforms during the test. 

Dyes differ from pigments in that dyes, but not pigments, are soluble or can be solubilized in the medium in which they are used. Prior to 1856, pigments were exclusively animal, vegetable, and mineral matter. With Perkin s introduction of the first synthetic dye, mauve, to the English textile industry, and the subsequent expansion of the synthetic dye market, the use of natural dyes on textiles was virtually eliminated. In 1993 almost 155 million kilograms of synthetic dyes were manufactured in the U.S. (Table 18.1). 

In addition to the dyebath, several auxiliary baths are used in batch textile processing to clean dyed goods and/or to fix the dye to the fiber. Considerable energy, water and chemicals are also wasted when these auxiliary baths are drained to the sewer. Plant pollution problems are also worsened by the additional effluent. Virtually all of the chemicals used in the auxiliary baths (sodium hydrosulfite and hydroxide, surfactants, etc.) are colorless, and thus do not lend themselves to simple... 

Ever since the discovery of the steam engine, the precipitation of insoluble calcium salts in boilers and pipes has been causing severe problems. Thus, the discovery that low concentrations of phosphoric, pyrophosphoric or bisphosphonic acids can prevent scale had enormous industrial importance. This information, combined with the characteristic ability of BPs to chelate virtually every heavy metal, laid the basis for their wide industrial importance [4], As a result, bisphosphonates are in current use in a wide variety of industrial areas, as scale inhibitors, for the treatment of metal and other surfaces, in water treatment, in the textile industry, in the detergent and cosmetic industry, in the polymer industry, and several others [4],... 

Related Calculations. The difference between the two internal rates of returns is so small that, on a purely economic basis, the projects are virtually indistinguishable. By contrast, the difference in the projects net present worths (see Example 18.5) is large enough to make the textile fibers expansion the clear choice for funding. As with the net present worth method, the internal rate of return procedure cannot be used unless the lifetimes of the competing projects are equal. 

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