Yarn mechanics

Fabric softness is the result of the skin-fabric interaction and of the fabric mechanical properties. Fabrics are made of yarns, yarns being assemblies of twisted fibers. Fabric mechanical properties depend on the fabric geometry, on the yarn-yarn friction, and on the yarn mechanical properties. The mechanical properties of the yarn are determined by the fiber rigidity, by the fiber-fiber friction, and by the yarn geometry [26],... 

Reinforcing fibers can be modified by physical and chemical methods. Physical methods, such as stretching [22], calandering [23,24], thermotreatment [25], and the production of hybrid yarns [26,27] do not change the chemical composition of the fibers. Physical treatments change structural and surface properties of the fiber and thereby influence the mechanical bondings in the matrix. 

W.D. Claus et al, Evaluation of the Mechanical Properties of Yarns for Ballistic Applications , Rept No USA-NLabs, C/PLSEL-TR-73-60-CE, 113, Contract DAA G17-70-C-0086, Fabric Research Labs Inc, Dedham (1973)... 

The observed luminescence properties of the copolymer yarns can be easily explained if an energy transfer mechanism is assumed to be operating (Figure 7). Triplet-triplet energy transfer from the terephthalate units to the 4,4 -biphenyl -dicarboxyl ate units explains both the dual fluorescent/phospho-rescent emissions from the 4,4 -biphenyldicarboxyl ate units as well as the quenched phosphorescence from the terephthalate units. 

A study of the relative fluorescence intensities at 460 nm of PET and PET-4,4 -SD yarns after receiving identical irradiation intensities reveals an increase in the formation of the hydroxyterephthaloyl moiety with increasing amounts of 4,4 -SD. This indicates that a photooxidative mechanism involving the second monomer may be an explanation of the increasing degradation rates. 

Figure 11. Possible photooxidative mechanism occurring in polyfethylene tereph-thalale-co-4,4 -sulfonyldibenzoate) yarns (34)...

Ghemes A, Minami Y, Muramatsu J, Okada M, Mimura H, Inoue Y. Fabrication and mechanical properties of carbon nanotube yarns spun from ultra-long multi-walled carbon nanotube arrays. Carbon. 2012 Oct 50(12) 4579-87. 

Miao M, Hawkins SC, Cai Y, Gengenbach TR, Knott R, Huynh CP. Effect of gamma-irradiation on the mechanical properties of carbon nanotube yarns. Carbon. 2011 Nov 49(14) 4940-7. 

Before weaving, the warp is covered with a layer of polymer to withstand the mechanical stress (abrasion, tension) during weaving. These polymer coatings are so-called sizes. Normally native starch, modified starch like carboxymethyl-starch (CMS), carboxymethyl-cellulose (CMC), polyvinylalcohols (PVA), polyacrylates, and proteins can be used. The amount of added polymer for staple yarns like Co is between 8 and 20% of the weight of the warp. As a result, in many cases the final amount of polymer to be removed in the desizing step is approximately 5-10% of the weight of the fabric. 

P. Marmey, M.C. Porte-Durrieu, C. Baquey, PVDF multifilament yarns grafted with polystyrene induced by gamma-irradiation Influence of the grafting parameters on the mechanical properties, Nucl. Instrum. Methods Phys. Res. B 208 (2003) 429-435. 

Tensile stages are used to observe the deformation mechanisms of materials in tension [1,45]. A common use of tensile stages in the study of polymers is to study the tensile failure of fibers and yarns [45]. Other modes of deformation such as binding and shearing can be studied with suitably modified stages [1]. 

The mechanisms by which materials change are of prime importance in determining the kinetics. Materials science and engineering emphasizes the role of a material s microstructure. Structure and mechanisms are the yarn from which materials science is woven [1]. Understanding kinetic processes in, for example, crystalline materials relies as much on a thorough familiarity with vacancies, interstitials, grain... 

The manufacture of acetate staple and tow follow the same scheme as employed for continuous filament yams, except that the yarns are combined as they leave the spinning tube to form a tow which is mechanically crimped and cut into staple lengths. Acetate and triacetate arc packaged in hales of about 4(X) pounds (181 kiltigrains). 

Different yarns of different physical and mechanical properties can be woven into the same fabric by adding creel behind the weaving machine or by adjusting filling yarn feeders. 

Basic yarn components along with conventional filaments/yarns constitute the feedstock of the weaving process. Selectively fed into a loom and manipulated through an advanced textile manufacturing process, this feedstock can be woven into a complex variety of designs that result in a structurally sound, environmentally compatible fabric that provides electrical and mechanical functionality. Electronic circuits can be formed from the selective interconnection of fibre components during the weaving process. 

Effect of Grafting Acrylonitrile to Cotton Yarn Under Various Conditions on the Mechanical Properties. (Taken from Blouin etal.) Ref. 29. 

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