In contrast to knitting, weaving or stitching, warp knitting is only familiar to a few. However, innumerable textiles are manufactured using warp knitting: curtains and lace lingerie, luggage racks and seat heating as well as satellite antennas and camouflage netting. The possibilities for using warp knitting are almost unlimited and range from open net structures to closed surfaces, from highly elastic and high-strength textiles to spacer textiles with functions inspired from bionics. This variety is not least of all attributable to the broad range of deployable materials which, combined into innumerable patterns, incorporate specific properties into the respective textile. One particularly outstanding property of warp knitting that is of interest for composites is the ability to integrate completely stretched, non-deflected threads and position them in a manner that is secure against displacement so that textiles are created without stretching related to the design.
Tec-Knit developed warp knitted camouflage netting that have been in use for the German armed forces since the year 2001. They were previously manufactured from punched PVC tarpaulins. The knitted fabric with its three millimeter openwork structure weighs less than 200g/m2 and is thus significantly lighter in weight than the PVC tarpaulins. In addition it has the advantage that it does not warm up and so it does not become visible as a hot-spot. The camouflage netting covers radar as both as near and far-infrared frequency ranges. A special coating also imitates the so-called chlorophyll curve, i.e. when the netting is evaluated it exhibits the same frequency ranges that are characteristic of chlorophyll in leaves. Metallized yarns are used because of their reflection properties as well as yarns with a share of carbon black for absorption. Since metallized yarns generally exhibit increased combustibility, special development requirements were necessary in order to achieve the requisite fire performance. Civilian applications now also benefit from these developments. Currently the netting is being further developed for portable personal protection. The light weight and breathing ability of the knitted fabrics are particularly remarkable in this case.
Adaptive camouflage is also currently under development because today’s camouflage nets appear to be too two-dimensional due to their unnatural regularity. In addition, large camouflage nets reflect the cold from outer space, so that they might be detectable as cold spots. Thus artificial vegetation that is actively cooled and heated is to imitate the heating up and cooling off of tufts of grass, for example, and be selectively positioned on the camouflage nets. It is also conceivable, but not yet under development, that the tufts of grass independently adapt to the respective temperatures.
Thermal Targets are also pursued based on the same technology. Thermal Targets are textiles with integrated heating which, for example, imitate the heat signature of tanks.
Mareike Gast is an industrial designer with her own business in Frankfurt, specializing in new materials and technologies. In close cooperation with industry and research, she develops innovative products and product strategies. In addition to her work in product development, she also regularly teaches at various international universities.