At present, all kinds of advanced weapons are developing towards stealth. Stealth technology is not only the shape design but also the stealth coating. Today we are going to talk about stealth coatings.
Stealth coatings, also known as radar absorbing materials, are an important way for weapons such as aircraft to gain stealth performance. Structural radar absorbing materials and electrostrictive stealth coatings are the two most concerned among many radar absorbing materials, and it can be said that there are only two kinds of radar absorbing materials with engineering value.
Structural radar absorbing material is a kind of multifunctional composite material, which has the advantages of light weight and high strength mechanism, and it also has the characteristics of strong absorption or transmission of electromagnetic waves. It is the main type of stealth material.
The structure of the fuselage and airfoil of the American B-2 Bomber is a kind of structural radar absorbing material, which has a non-circular section of carbon fiber and honeycomb sandwich composite structure. The density of the absorbent material increases from the outside to the inside, while the multilayer permeable mask is used as the interlayer, and a resistive plate is embedded between the cover and the honeycomb core, all of which allows radar waves to be absorbed into the cell core when they are irradiated to B-2 by a multilayer transparent skin.
With the development of composite material technology, new structural radar absorbing materials emerge. New thermoplastic materials such as PEEK, PPS, PES, and thermosetting epoxy, polyimide, double maleic imide, isocyanate, and polyetherimide have become the ideal material of stealth coatings.
The electrostrictive stealth coating is usually composed of carbon, SiC powder, metal or gold-plated fiber as absorbent and dielectric polymer as adhesive, which has the advantages of lightweight, high-frequency absorption and so on. However, this material needs to be coated with a larger thickness, so it is difficult to achieve the thin layer of broadband absorption, which limits the application of it. At present, there are no reports of pure electric loss stealth coatings for aircraft.
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