Effect of a gold coating on the mechanical properties of a Microwire, applied for knitting of the large transformable antennas

Knitted materials made of a microwire are widely used in space systems as reflecting surfaces of transformable parabolic reflector antennas. To increase the reflecting properties and improve the radio-technical characteristics of the antenna, the microwire is usually covered with a gold layer of about 0.2 microns thick. However, according to the theoretical calculations and experimental investigations, when a large antenna hits streams of stationary plasma engines of the satellites, the dispersion (erosion) of the gold covering occurs. The erosion magnitude can reach several microns. Since the covering thickness which defines the reflection factor of the radar-reflecting surface is about one-tenth of a micron, the erosivity of the specified streams can significantly reduce the efficiency of the antenna. In this regard, an increase in the coating thickness to at least 1 micron or even more is required. Since large antennas are knitted from a tungsten microwire with 15 microns in diameter, it is necessary to estimate the effect of the gold covering of 1 micron thick or more on the bending moment of such microwires, shape recoverability after a bend, and permanent deformation after a plastic bending. In this paper, the effect of the gold coating thickness on the bending diagram of a tungsten microwire of 15 microns in diameter is theoretically considered. It has been revealed that the coating of about 2 microns thick has essentially no effect on the bending diagram of the tungsten microwire and, therefore, does not significantly affect the physical-mechanical properties of the reflecting surface of antennas knitted from such a microwire.

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