RU2275719C1 - Radio-absorbing material - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: proposed radio-absorbing material that can be used for covering metal platforms of antenna systems to attain desired characteristics of these systems operating with radome, for instance, to reduce angular error in bearing brought in by radome is made in the form of glass-fabric reinforced ring and incorporates in its composition process carbon and foamed polyurethane as polymeric base, their proportion complying with formula given in description of invention. Specific mass of material is 0.4 g/cm³.

EFFECT: enhanced operating serviceability at vibration loads, high humidity, reduced atmospheric pressure, and cyclic temperature fluctuations.

2 cl, 1 dwg, 1 tbl

Description

The present invention relates to the field of radio engineering and can be used to cover metal platforms of antenna systems.

Currently, there are no commercially available lightweight radar absorbing materials designed to achieve the required characteristics of antenna systems when working with a cowl (for example, reducing the angular error of a bearing introduced by a protective cowl).

The most common absorbent components are: industrial carbon (soot), graphite, carbonyl iron, and dielectric materials as a bonding base.

Existing radar absorbing materials based on carbonyl iron and dielectric materials, for example, type XB-3,2; PM-3.2, etc., are performed with certain dielectric and magnetic permeabilities. These materials are heavy and they can not always be used in aircraft and rocket technology. Known, for example, wedge-shaped, conical and pyramidal volumetric absorbers of electromagnetic waves, the application of Germany No. 159114, MKI H 01 Q 17/0, 1972. In this application, the absorber is made of foam with fillers. Shaped elements are cut from the foam (absorbing plates, which consist of a base plate with a square surface and wedge-shaped, conical or pyramidal absorbing elements towering above the base). Absorbing plates are immersed in a mixture of varnishes with graphite or carbon black filler; in addition, adhesives used to bind the filler and an anti-foaming agent are included in the absorber.

A disadvantage of the known absorbers is that they have a large specific gravity due to the additionally introduced mixture of varnish and adhesives, as well as instability of characteristics depending on the quality of the impregnation.

Of the known materials, the closest in technical essence and the achieved effect is the material described in the express information Radio Electronics Abroad, issue 2 (1104), 1988, pp. 15-16; new single layer absorbent material. The material developed by the specialists of Spare Aerospace (Canada) is a rubber filled with acetylene black, which can be made in the form of thin panels and, due to its flexibility, can be easily applied on curved surfaces.

This absorber satisfies the radio technical characteristics, it is lighter than the radio-absorbing material with carbonyl iron, but it is still difficult to use in antennas for aircraft and rocket technology.

The article "Modern Radiolucent and Radar Absorbing Materials," Journal of Radio Electronics Abroad, Moscow, 1990, issue 7 (47), pp. 46-49, describes radar absorbing materials containing foams as binders, including polyurethane foams, encased in fibrous material.

The objective of the invention is to reduce the specific gravity of the radar absorbing material without compromising the radio characteristics of the antenna systems when working with a cowl, for example, the magnitude of the angular error of the bearing.

The problem is achieved in that in the radar absorbing material containing the filler - technical carbon particles, a polymer base is used - polyurethane foam in the following ratio of components, wt.%:

polyurethane foam 82.23-88.47 carbon technical rest

When studying other technical solutions in this technical field, it is seen that technical carbon is used in a radar absorbing material. However, its use in combination with polyurethane foam in certain proportions is not known. At the same time, a new positive effect is formed - a decrease in the weight of the radar absorbing material while maintaining the radar absorbing characteristics.

For experimental verification, 6 absorbent compositions were prepared with different contents of polyurethane foam, technical carbon and carbonyl iron, which are shown in table 1.

Table 1 Name of components Options for the composition of the components in the absorber, wt.% No. 1 Number 2 Number 3 Number 4 Number 5 Number 6 Polyurethane foam 88.47 79.33 64.94 88.47 82.23 93.85 Technical carbon rest rest - - rest rest Carbonyl iron - - rest rest

As a result of the check, it was found that the lowest specific gravity and identical materials PM-3.2 and XB-3.2 absorbing properties in the product in a given frequency range have a radio-absorbing material with carbon technical (options for the composition of components No. 1, 5 in Table 1) .

To select a rational design of the absorber, several absorbers of various configurations were made by machining from the panel and tested in the composition of the product.

The requirements of the product are best satisfied by the design of the absorber in the form of a ring 5 mm thick, 38 mm wide (0.8 λ _cf ) (d _ext = 132 mm, d _nar = 170 mm).

The angular error of the bearing, measured in the composition of the product in the presence of a ring of a selected design made of absorbing materials PM-3.2 (XB-3.2) or a fiberglass reinforced ring of polyurethane foam with technical carbon, decreases by 1.5-2 times and practically does not depend on the type of absorbing material used. The use of polyurethane foam and technical carbon in the radar absorbing material allowed to reduce the weight of the material, since the specific gravity of the absorber is 0.4 g / cm ³ . The specific gravity of analogues:

XB-3.2 - 3.09 g / cm ³ ;

PM-3.2 - 2.84 g / cm ³ .

Prepared a mold for pouring polyurethane foam with carbon technical. An SPT-3 fiberglass gasket was placed in the mold matrix and on the lid. The fill surface of the gaskets was varnished with UR-231. Polyurethane foam and technical carbon were thoroughly mixed for 1-2 minutes, the resulting mass was poured into a mold, and cured according to OST 4GO 054 234 in the following mode:

at a temperature of 200 ° C - 2 hours,

at a temperature of 220 ° C - 5 hours.

The mold was cooled to a temperature of 40 ± 10 ° C, the ring was removed from the mold and the flask removed. In a fiberglass reinforced polyurethane foam ring with carbon technical holes were drilled according to the drawing.

Assembled a device for gluing bushings into the holes of the ring and ring to the metal panel. Gluing was performed with K-400 glue according to OST 4 G0.054.210.

Next, tests were carried out on a product with a fiberglass reinforced ring made of a radio-absorbing material based on polyurethane foam with technical carbon.

In normal climatic conditions, a check was made of the appearance, overall and docking dimensions, mass measurement, and electrical parameters at nominal supply voltages. Checking the product parameters was carried out during the tests:

- on the effect of low ambient temperature:

a) at a temperature of -55 ° C - 4 hours,

b) at a temperature of -60 ° C - 1 hour.

After the specified time, the temperature in the chamber was raised to normal, at which it was held for 2 hours, after which the parameters were measured.

- moisture resistance at high humidity for 9 cycles of 24 hours, each of which consists of 2 stages:

a) at a temperature of + 55 ° C and relative humidity (100%) - 12 hours,

b) at a temperature of + 35 ° C and relative humidity (100%) - 12 hours.

In the process of testing, every 3 cycles the product was checked for operability.

- tests for the effects of changes in ambient temperature:

a) in a cold chamber at a temperature of -60 ° C - 4 hours,

b) in a heat chamber at a temperature of + 80 ° C - 4 hours.

Three cold-heat cycles followed one after another continuously.

- tests for exposure to elevated ambient temperature:

a) at a temperature of + 60 ° C - 3 hours,

b) at a temperature of + 80 ° C - 2 hours.

- tests for exposure to low atmospheric pressure:

a) at a temperature of -60 ° C - 3 hours,

b) lowered the pressure to 14 mm Hg and kept for 1 hour.

- tests for mechanical factors:

mechanical shock repeated action, resistance to mechanical shock, resistance to random broadband vibration, resistance to linear acceleration.

As a result of the tests, it was found that all the parameters of the product with a fiberglass reinforced ring of a radar absorbing material made of polyurethane foam filled with technical carbon meet the requirements of TK and TU for the product.

The dependence of the angular error of the bearing in the presence and absence of fiberglass reinforced rings of radar absorbing material made of polyurethane foam and carbon black is shown in the drawing.

Thus, the use of the claimed radar absorbing material made it possible to reduce the maximum angular error of the bearing by 0.16 °, the maximum slope of the angular error of the bearing by 0.02 deg / deg, to reduce the specific gravity of the radar absorbing material, to increase manufacturability by eliminating the mechanical processing of PM-3.2, ХВ absorbers -3.2, supplied as plates.

Claims (2)

1. Radar absorbing material containing filler - technical carbon particles and a polymer base - polyurethane foam, characterized in that it is made with the following ratio of components, wt.%: Polyurethane foam 82.23-88.47 Technical carbon Rest 2. The radar absorbing material according to claim 1, characterized in that it is made in the form of a 5 mm thick reinforced fiberglass ring.