JPS6012803B2 - Membrane material for radome - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a metal space frame radome.

The performance of a radome, which protects a radar antenna from wind, rain, snow, etc., is evaluated based on radio wave transparency, radio wave deviation, durability, etc., and its characteristics are determined by the constituent materials and structure of the dome.

In recent years, a metal space frame radome has been newly developed with the aim of improving radome performance.

That is, a metal frame is used as the strength member of the entire radome, and a membrane with good radio wave characteristics stretched between the frames serves as a radome by protecting it from wind and rain. Compared to traditional radomes, metal space frame radomes are
Radio wave loss and lightning wave deviation are reduced, and radome performance is significantly improved.

The present invention relates to a membrane material used in this metal frame radome.

When considering the membrane material for metal space frame radomes, the following points must be taken into consideration: 1) good radio wave transparency, 2) relatively high strength, and 3) impact resistance even in the form of a membrane. Excellent.

4) Due to the connection with the metal frame, it is necessary to have a certain degree of flexibility.

Reinforced membranes made by soaking glass cloth with epoxy resin, polyester resin, etc., used in conventional radomes, have relatively high rigidity and cannot be used as membrane materials for metal frame radomes due to poor impact resistance.

The present invention relates to a membrane material used in metal space frame radomes, which is made of EP rubber (ethylene-propylene rubber and ethylene propylene terpolymer) reinforced with inorganic fibers or organic fibers.

EP rubber is very stable, and is widely used in electric wire parts, etc. as a rubber with particularly excellent film resistance, and also has relatively excellent electrical properties. The membrane material for the radome is made of EP rubber as a matrix and reinforced with inorganic fibers (e.g. glass fiber, ceramic, alumina, etc.), organic fibers (polyamide, polyester, etc.), long fibers, woven cloth, chopped, etc. be. By applying this film material to a metal space frame radome, it is possible to reduce radio wave loss and radio wave deviation and improve the performance of the radome. Especially E
Due to the superiority of P rubber, it has excellent weather resistance and can fully satisfy long-term requirements as a structure. EP at the same time
Due to the elutriation properties of rubber, it has particularly excellent impact resistance, and can be easily attached to a frame. EP rubber can be molded using conventional rubber-coated cloth, and the membrane material can also be molded using methods such as dipping and rolling spread.

A wide range of fibrous materials such as organic fibers and inorganic fibers can be used, but considering the usage conditions, it is desirable to use materials that have relatively little elongation and are resistant to bending.

In particular, with regard to elongation, as shown in the examples, particularly excellent effects are exhibited when the elongation at break is 5% or less.

In other words, the organic-inorganic fiber material has a high modulus with an elongation at break of 5% or less. Its properties are extremely good, and permanent elongation (creep) due to loads and initial loads caused by wind during use can be virtually ignored, making it less susceptible to flapping due to wind, which is extremely advantageous in terms of strength design. However, such fibrous materials generally have poor bending fatigue properties, and connection with metal frames becomes a problem. For this reason, we have discovered that a metal-based frame radome can only be made possible by covering it with EP rubber, which has excellent flexibility. Furthermore, in order to maximize the characteristics of a metal space frame radome, if there is any sagging in the membrane material, which is applied with uniform tension, the durability will be extremely poor. Therefore, the initial tension is applied to the membrane material (usually a load of 1/20 to 1/40 of the breaking strength).
It is necessary to prevent sagging by applying With a high modulus of elongation of 5% or less, the elongation (strain) when the initial load is applied is extremely small and uniform, preventing flapping due to wind and improving durability.If the elongation exceeds 5%, the elongation (strain) when the initial load is applied It has been found that several percent of strain occurs, which is extremely disadvantageous in terms of durability. From this point of view, recently developed aromatic polyamide-based high elastic yarns (for example, Dupon't
Kevlar fibers, etc.) are the materials of choice.

Example EP rubber was made into Kevlar 49 (Dupo
n't Co.) #281 cloth was impregnated to prepare a sheet.

When the physical properties of this sheet were confirmed, the tensile strength was 70k9/
A performance of over 5% elongation and 95% or higher radio wave transmission was achieved.

Claims (1)

[Claims] 1. A metal space frame radome characterized by using an EP rubber matrix, inorganic fibers and organic fibers as reinforcing materials, and a membrane with an elongation of 5% or less.