Warp-Knitted Spacer Fabrics

The production of warp-knitted spacer fabrics is similar to that of knitted spacer fabrics. We also have two basic fabrics that are connected by pile yarns as shown in Fig. 5.22. 

This kind of fabric is produced on double-Raschel machines consisting of two machine sides that work independently. Each machine side produces one basic fabric that is then connected to the other basic fabric via pile threads supplied by one or more additional guide bars. The fabric is taken up inside the machine. 

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Warp knitting technology is the most commonly used technology for the production of spacer fabrics. Warp-knitted spacer fabrics have attracted great attention due to their low cost, high productivity and wide structure variations compared to other kinds of spacer fabrics. The critical characteristic distinguishing warp-knitted spacer fabrics... 

Warp-knitted spacer fabrics are produced on double-needle bar Raschel machines the principle is schematically shown in Figure 6.22(a). While the guide bars 1 and 2 lap the front-needle bar, and the guide bars 5 and 6 lap the back-needle bar, to knit the top outer layer and the bottom outer layer, respectively, the guide bars 3 and 4 lap the spacer yams around both the needle bars in succession. A spacer fabric being produced on a double-needle bar Raschel machine RD 6 by Karl Mayer is shown in... 

Figure 6.23 Photographs of a warp-knitted spacer fabric.

Weft-knitted and warp-knitted spacer fabrics can be used as sound absorbers to reduce the noise level in building, automotive and other places (Liu and Hu, 2010). Figure 6.28 shows a weft-knitted spacer fabric (a) of multifilament spacer yams and a warp-knitted spacer fabric (b) of monofilament spacer yams for sound absorption. Whereas the weft-knitted spacer fabric exhibits the typical sound absorption behaviour of porous absorbers, the warp-knitted spacer fabric exhibits the typical sound absorption behaviour of microperforated panel (MPP) absorbers. Figure 6.29 shows the noise absorption coefficients of the two spacer fabrics without and with air-back cavity. The combinations of weft-knitted and warp-knitted spacer fabrics can significantly improve their sound absorbability, as shown in Figure 6.30. 

Figure 6.28 Weft-knitted spacer fabric (a) and warp-knitted spacer fabric (b) for sound absorption.

Figure 6.31 Effect of different structural parameters on cushioning properties of warp-knitted spacer fabrics (a) spacer yam inclination (b) spacer yam diameter (c) fabric thickness and (d) outer layer structure (L, locknit Cl, chain plus inlay RM, smaU-size rhombic mesb HM, large-size hexagonal mesh).

Spacer fabrics are composed of numerous spacer yams. Each spacer yam functions as an Euler s rod, which can be engineered to mitigate vibration to suit different applications (Virgin and Davis, 2003). Eigure 6.32 shows the transmissibility of three warp-knitted spacer fabrics A, B and C with a thickness of 13.31,15.14 and 19.46 mm, respectively (Liu and Hu, 2011b). The results indicate that such fabrics are very suitable for vibration isolation. The fabrics can be used to produce antivibration gloves, wheel chair cushions and so on. 

Warp-knitted spacer fabrics have been used in energy and resource fields. Researchers from the ITV Denkendorf in Germany applied a layer of white warp-knitted spacer... 

Figure 6.32 Vibration transmissibility of warp-knitted spacer fabrics.

D knitted textiles have already been widely used as technical textiles in different fields. The future work should be on the development of new 3D knitted structures with more extra functions to meet the requirements of new application fields. For example, warp-knitted spacer fabrics have great structural variations. By using different structures and fibre materials, they have been developed to have various physical functions to be used in different fields, such as cushioning, sound absorption, smart textiles and thermal collection. New potential application fields should be identified first in the future, and then fabric stmctures can be designed to better match the specific applicatimis. 

Liu, Y.P., 2013. A study of warp-knitted spacer fabrics as cushioning materials for human body protection. Ph.D. dissertation. The Hong Kong Polytechnic University. 

Liu, Y.P., et al., 2012a. Compression behavior of warp-knitted spacer fabrics for cushioning applications. Text. Res. J. 82, 11-20. 

Vassiliadis, S., et al., 2009. Numerical modelling of the compressional behaviour of warp-knitted spacer fabrics. Fibres Text. East. Eur. 17, 56-61. 

For an illustrative representation of all the aforementioned aspects, examples of individual products are shown. Products like shoes, underwear, diving clothes and other applications are partly composed of 3D textiles, which are in most cases warp-knitted spacer fabrics. In addition to warp-knitted spacer fabrics, knitted spacer fabrics are also processed. The individual design allows the manufacmrer to combine more demands on the products and thus cover a wide range of applications. Generally there is great diversity in the field of sports and leisure clothing. 

An article (Anon., 2002b) has reported on the possibility to produce cloth shoes with warp-knitted spacer fabrics on the Raschel machine. Prefabricated products and the application of various functional zones can be realized if the machines are equipped with a Jacquard pattern. The Jacquard pattern is a binding technique in which each warp thread is individually controlled allowing for a maximum range of production possibilities. The subsequent processing, for example, laminating, is easily possible. Examples are shown in Section 14.2.2. 

The patent (Muller, 2009) includes the invention of a warp-knitted spacer fabric as well as a method for its production. Further information can be found in the patent (MiUler, 2009). 

Figure 14.8 provides an example of a warp-knitted spacer fabric with good breath-abihty and damping properties. 

Protective clothing for extreme sports such as downhill mountain biking, extreme skiing and snowboarding are made of breathable warp-knitted spacer fabrics with particularly dimensional stability (Anon., 2007a). 

The invention in the patent (Heide et al., 2006) refers to a 3D warp-knitted spacer fabric with native, for example, cotton and/or synthetic fibres. 

Figure 14.10 3D warp knitted spacer fabric production. 

In addition to the test methods for thermophysiological parameters, there are test methods to measure the mechanical properties of the warp-krutted spacer fabrics. Among other things, the buckling behaviour and the rigidity of the warp-knitted spacer fabrics are of significant interest because they characterize the freedom of... 

As mentioned earlier, warp-knitted spacer fabrics are used in most shoes. From the classic running shoe to more specialized barefoot-shoes, stability is the most important attribute. The connection between fashion and functionality can be implemented particularly well by the warp-knitted spacer fabrics. The sporting goods manufacturer Nike Inc., in Beaverton, Oregon, was the first to successfully establish a shoe with portions of warp-knitted spacer fabric and marketed it in the year 2002. 

The Nao brand from Brazil mainly manufactures leisure shoes made from warp-knitted spacer fabrics. These shoes are very light and offer a high wearing comfort due to breathable warp-knitted spacer fabrics on the surface. Figure 14.12 shows a model of the Brand Nao. Figure 14.13 shows an enlarged view of the warp-knitted spacer fabric used in the shoe. 

There is a great potential for the use of warp-knitted spacer fabrics in diving suits. Various manufacturers have dealt with this development. An article (Anon., 1998) describes an undersuit for a diving suit made of warp-knitted spacer fabrics in 1998. In contrast to the classical material neoprene, warp-knitted spacer fabrics... 

Figure 14.12 Shoe with warp knitted spacer fabric hy Nao.

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