Weft yarns

Figure 1, Strength retained of warp and weft yarns from fabric 605 (Lot 1) as a function of heating time at 150 °C. Key O, warp A, weft.

A plot of the logarithm of the degradation as a function of time for a first-order reaction produces a straight line. Such plots for the warp and weft yarns are shown in Figure 2. The plots are nearly linear and suggest that the degradation is indeed first order. As is well known in kinetics, the rate constant can be estimated from the slope of the line whose equation is given by... 

Table I. Breaking Load of Warp and Weft Yarns Extracted from Treated and Untreated Silk Fabric Lot 2...

When making very dehcate materials it may be necessary to use a yam which is so fine that it would break down under the stresses imposed on it during manufacture. The strength, however, is sufficient once the fabric is made because of the mutual support of adjacent threads. In such cases it is customary to impart temporary strength to the yam by a process known as sizing. This consists of impregnating the thread with some easily removed substance such as starch or dextrine and, in the case of the more modern man-made fibres, with a synthetic product such as polyvinyl alcohol or polyacrylic acid. The size is usually removed before the article is dyed or bleached. Yarns are frequently referred to as warp or weft yarns. In a... 

To constmct the same description for a weft yam, the intersection codes and parameters of crimp intervals of warp are used. Consider a weft yarn i at layer /. First, looking up the lists of crimp interval parameters, find the first warp that has in its lists /j = 1 or... 

I (i.e. supported by the weft yarn i at layer /) This would be the left end of the first crimp interval on the weft yam. The support warp number is thus found, and the position sign of the weft would be inverse to the position sign of the warp. Then find the next warp yam supported by the weft (/,/). This would be the right end of the first crimp interval on the weft yam, and the left end of the second crimp interval. Continue until all the crimp intervals would be defined. Note that in multilayered stmctures the number of crimp intervals on a weft yarn can be smaller than the total number of the warp zones. For example, the first weft yam in the first layer of the weave. Figure 2.2(a) (eight warp zones) has only five crimp intervals, as it does not intersect with three of the Z-yams. 

Fig. 5). The advantage of the Chain-weave is on the one hand that it does not easily get warped. On the other hand, this structure makes it hard to impregnate the textile with a high viscous polymer without having the entire structure covered with polymer. The Tricot-weave has large spaces between the warp- and weft yarns because the knitting thread is laid around the single warp fibers. Although this structure it gets warped very easily.

Woven fabrics are constructed by interlacing warp and weft yarns, fibres or filaments in a variety of patterns to form fabric styles such as plain, twill, satin, unidirectional and others. Woven fabrics are usually lighter than woven rovings, have less crimp and may achieve volume fractions of over 50% depending on the method of composite compaction. 

This is a modification of plain weave in which two or more ends and picks weave as one, moving one yarn for each end or pick (Figure 21.8). It is more dense than plain weave and more flexible, tends to abrade more readily and is not as strong as a plain weave. If two warp yarns pass over and under two weft yarns, this gives a 2 x 2 basket construction. The first... 

The warp and weft yams are positioned without being interlaced (Figure 21.13). A second set of finer warp and weft yarns binds them together, but does not contribute to the mechanical performance of the fabric. This eliminates the crimp and shear factor. 

Figure 16.9 represents the whole shaping process applied to a woven polyester fabric (warp yarn count 100 dtex/90 fil, weft yarn count 60 dtex/55 fil). A vacuum pump was used to remove the air from the volume defined between the plastic membrane and the device. As can be observed in Fig. 16.10, which represents the fabric after sheathing and the deformation undergone by a network of lines initially drawn on the tubular element. 

No changes in fabric dimensions and, therefore, in fabric count were observed. Accordingly, the rearrangement occurred only at the level of the warp yarn the overall fabric construction was not affected by the rearrangement mechanism. Since weft yarn did not undergo changes, either in crimping or in yarn cross-section, the fabric thickness measured was no different after... 

Plain woven structures (a) fabric showing warp and weft yarns with crimp due to interlacings at the cross-over points and (b) finished prostheses with warp along and weft across the graft axis. 

Effect of denting order (DO) on weft yarn crimp, (a) high denting order and crimp and (b) low denting order and crimp. 

Six 180 gsm fabrics were selected, comprising a variety of exotic animal hair fibres (mohair, alpaca and cashmere) and Sea Island cotton as weft yarns and silk or polyester warps ... 

Plain weave is the simplest interlacing pattern, as shown in Fig. 8.22 for jute and coir woven geotextiles in the length of the fabric a warp yam crosses over alternate wefts, and in the fabric width, a weft yarn crosses alternate warps. The frictional contact of the yarns at the interlacing points prevents each yarn slipping from its woven position, and it also increases the stiffness of the fabric. The interlacing causes the warp and weft yarns to have a... 

Let dp and = the width of the warp and weft yarns as projected, and Pp and Pf = the pitch of the warp and weft yarns as projected. 

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