Textile mechanics

Key words hbre, yarn, woven fabric, knitted fabric, non-wovens, design of experiment, hypothesis testing, analysis of variance (ANOVA), regression analysis, geometrical models, structural models, fibre migration, unit cell, knot invariants, textile mechanics, physical properties of textiles, homogenization, optimization. 

It can be seen from a number of publications on textile mechanics that the modelling methods progressed from force and torque equilibrium analysis to energy methods and to the finite-element and RVE analysis. This trend can be traced through the entire range of textile products, from yams to woven, knitted, braided and non-woven fabrics, and to composites. 

Modelling physical properties has many common points with that of the textile mechanics. First of all, the structural arrangements at micro- (fibre), meso- (yarn), and macro-levels (fabric) need to be modelled. Similar to Section 1.6, the structure can be considered at different levels of detail and a choice should be made between discrete and continuous models. In contrast to modelling the textile mechanics where the structure modelling is concentrated on fibres and yams, the distribution of dimensions and orientation of voids (pores) between the fibres and yams is important for models of fluid flow. Closely related to this are models of filtration where in addition to the distribution of dimensions and shapes of particles, their interactions with the fibrous structure should be considered (Chemyakov et al, 2011). 

During the last 25 years, the applied mechanics of composites has developed in a major way. The starting point was mixture laws, which were then applied to short fiber systems by considering aspect ratios and orientation distributions, and to long fiber systems by laminate theory. The total component behaviour is then handled by finite element methods. However this approach is not right for an interlaced assembly, and it is appropriate to look at the development of textile mechanics, which has occurred in the last 40 years. 

The integration of electronics to wearable technology on a textile platform requires a multidisciplinary approach that includes expertise in the fields of materials, textiles, mechanical, electrical and electronics, and information technology. Electrical conductivity can be integrated into textiles platforms (Courtesy of Bally Ribbon... 

The antimicrobial activity of chitosan against microorganisms of a wide variety of bacteria and fungi has long been recognized [42]. This unique property has led to many potential applications to food science, agriculture, paper, medicine, pharmaceuticals, and textiles. Mechanisms behind the... 

Many polymeric materials may be spun into fibers, which are used primarily in textiles. Mechanical, thermal, and chemical characteristics of these materials are especially critical. 

Uses Defoamer in metalworking, cosmetics, paper, textiles, mechanical dishwashing detergents and rinse aids lubricant base in fomtulating syn. metalworking... 

In the RQD work at ATIRA the computer is often used to design and develop textile mechanisms as well as to simulate textile weaves. To... 

A schematic stress-strain curve of an uncrimped, ideal textile fiber is shown in Figure 4. It is from curves such as these that the basic factors that define fiber mechanical properties are obtained. 

An important aspect of the mechanical properties of fibers concerns their response to time dependent deformations. Fibers are frequently subjected to conditions of loading and unloading at various frequencies and strains, and it is important to know their response to these dynamic conditions. In this connection the fatigue properties of textile fibers are of particular importance, and have been studied extensively in cycHc tension (23). The results have been interpreted in terms of molecular processes. The mechanical and other properties of fibers have been reviewed extensively (20,24—27). 

R. Meredith, Mechanical Properties of Textile Fibers, Interscience Pubhshers, New York, 1956. 

The mechanical properties of acryUc and modacryUc fibers are retained very well under wet conditions. This makes these fibers well suited to the stresses of textile processing. Shape retention and maintenance of original bulk in home laundering cycles are also good. Typical stress—strain curves for acryhc and modacryUc fibers are compared with wool, cotton, and the other synthetic fibers in Figure 2. 

The ratio of stress to strain in the initial linear portion of the stress—strain curve indicates the abiUty of a material to resist deformation and return to its original form. This modulus of elasticity, or Young s modulus, is related to many of the mechanical performance characteristics of textile products. The modulus of elasticity can be affected by drawing, ie, elongating the fiber environment, ie, wet or dry, temperature or other procedures. Values for commercial acetate and triacetate fibers are generally in the 2.2—4.0 N/tex (25—45 gf/den) range. 

Fibrillated Fibers. Instead of extmding cellulose acetate into a continuous fiber, discrete, pulp-like agglomerates of fine, individual fibrils, called fibrets or fibrids, can be produced by rapid precipitation with an attenuating coagulation fluid. The individual fibers have diameters of 0.5 to 5.0 ]lni and lengths of 20 to 200 )Jm (Fig. 10). The surface area of the fibrillated fibers are about 20 m /g, about 60—80 times that of standard textile fibers. These materials are very hydrophilic an 85% moisture content has the appearance of a dry soHd (72). One appHcation is in a paper stmcture where their fine fiber size and branched stmcture allows mechanical entrapment of small particles. The fibers can also be loaded with particles to enhance some desired performance such as enhanced opacity for papers. When filled with metal particles it was suggested they be used as a radar screen in aerial warfare (73). 

The film is fibrillated mechanically by mbbing or bmshing. Immiscible polymers, such as polyethylene or polystyrene (PS), may be added to polypropylene to promote fibrillation. Many common fiber-texturing techniques such as stuffer-box, false-twist, or knife-edge treatments improve the textile characteristics of slit-film fibers. 

In the Philippines, the principal suppHer of abaca fiber, the fibrous layer ia the sheath is separated with a knife between the layers, and the strips of fiber-containing layers, called tuxies, are pulled off and cleaned by hand to remove the pulp. In Indonesia and Central America these operations are performed mechanically. Hand- and spiadle-stripped fiber is graded for braids, fine textiles, and cordage decorticated fiber is another class. A cross-sectional view is shown ia Figure 4a. The abaca fiber has a large lumen and the presence of siUcified plates is not unusual. 

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