Protecting Signal Strength Using Polyurethane Foam

Radome structures protect radar equipment across many applications, ranging from boats and aircraft to defense and solar system research. These weatherproof shells transparent to radio frequency systems, notably radar, microwave, and other antennae, are used for signal transmission and capture that do not affect the signal passing through them.

Although “radome” is a combination of ”radar” and “dome”, these protective structures are not always dome-shaped but are available in different shapes, including flat panels covering sensitive components of antennas on small radar systems used in naval systems and on large dishes.

Polyurethane foams manufactured by General Plastics are mostly used as composite materials and exhibit dielectric properties that find applications in the construction of radomes and related housings. They act as an optimal, insulation-providing barrier between sensitive electronics used in radar systems, telemetry, and communication and threats posed by the environment such as wind, snow, rain, hail, insects, UV damage, sand, bird strikes, and rapid fluctuations in temperature.

Wide-Ranging Dome Applications

  • Commercial aircraft – Commercial airplanes depend on signals for navigation or communications. Radomes used in protective structures present on the noses of aircraft ensure optimum antenna functionality for weather detection.
  • Broadband communications – Radomes extending to more than 3 m in diameter on large cruise ships and oil tankers may cover antennas connecting them to Internet transmissions, voice, and data television.
  • Stationary antennas – Radomes prevent ice, debris, and freezing rain from accumulating directly onto the surface of the metal.
  • Private yachts – Small, private yachts may use radomes as small as 26 cm in diameter for voice and low-speed data purposes.
  • Security/military/defense – Radomes protect electronic surveillance equipment such as those used to intercept satellite communications and other radar air defense applications, by concealing the equipment. They also support military aircraft platforms for electronic warfare, reconnaissance, defense and pre-emptive strikes, electronic countermeasures , and data links.
  • Solar system research – Radar dishes are used by NASA in far-flung reaches and uninhabitable areas that offer minimal signal pollution.
  • Maritime satellite communications – Ships use radomes to shield dish antennas used for continuous tracking of fixed satellites and for navigation.

Why Polyurethane Forms are Optimal for Constructing Effective Barriers

Radomes are built using suitable materials and configured properly for the desired application and radio frequency range are electronically invisible, preventing a negative impact on the performance of the produced or captured signals. Robust, cost-effective and versatile, the polyurethane foams from General Plastics provide high performance and low dielectric interference with excellent dimensional stability. There are two reasons for the foam materials to not change over time: they are closed-cell and hydrophobic, i.e., they do not absorb water. Water is highly polar and can cause the materials to lose or change their properties over time.

Additionally, foam structures surrounding radar dishes prevent their movement caused by wind and snow in extremely cold and windy environments. Foam material is a natural insulator and prevents the transfer of cold and heat which substantially slows down potentially undesirable variations in temperature. For instance, during the transition from night to day, an unprotected antenna may heat up quickly under direct sunlight, affecting its longevity and performance.

Radomes are mostly fabricated by using layup or prepreg methods, wherein resin-reinforced laminate materials are readily bonded to low or medium-density, rigid polyurethane foams. General Plastics’ polyurethane foams are known for supporting composite structures, which leverage their high strength-to-weight ratio.

Selection Considerations

The foam materials supplied by General Plastics possess unique characteristics and advantages that are useful to determine their applications. Specific foam from the company features low loss tangent and low dielectric constant, making it perfect for radome applications. In addition, material selection may rely on several factors such as the contours or shapes of the sensitive electronic components being covered and how important it is to protect them. General Plastics offers polyurethane foams such as LAST-A-FOAM® FR-3700 Performance Core series and FR-7100 Multi-Use Core series that are best suited for these applications.

LAST-A-FOAM® FR-3700 has specifically-engineered properties that make it more durable and tougher than the FR-7100. The FR-3700 can handle rugged environments for a given density, such as those required for defense and military applications that command the highest levels of protection. This performance core series is resistant to most chemicals and solvents, an excellent alternative to wood, flame-resistant, and possesses a high strength-to-weight ratio.

The LAST-A-FOAM® FR-7100, although not as tough as the FR-3700, is adequate and more suitable for applications involving reduced risk. Other advantages of this multi-use core include dimensional stability, its closed-cell characteristic that does not absorb moisture or water, and fine cell structure that supports smooth finishes. FR-7100 is recommended for applications that have less performance requirements and enable more variation.

Generally, larger radomes have simpler exposure requirements. For instance, a very large radome in Alaska only has to control some wind and potentially hail, while a weaponized system or a naval ship will require a tougher, more significant composite to shield that radar system from loss. This is also a function of density driving and foam formulation material properties.

Proven Capabilities

General Plastics’ signature LAST-A-FOAM® materials were subjected to tests, which showed the effective performance of the foams under a range of applied microwave frequencies without any considerable heat loss. The company’s products have been shown to be impervious to moisture and almost transparent to radio signals. They are the most preferred choice for protecting marine, land-based microwave, and aerospace antennas

General Plastics provides urethane foams in three ways: 1) machined to shape, based on a given drawing with dimensions noted; 2) as a molded part; and 3) as sheet stock that can be further modified to satisfy customer demands.

Irrespective of whether users are choosing foam material in blocks or boards, or depend on General Plastics for finished or machining products, they are advised to contact the company’s Customer Solutions team during the early stages of the design process. Since each query might be specific, users can tap the company’s expertise beforehand to identify the design's impact on cost. To provide valuable guidance, the company has technical data sheets for each product.

This information has been sourced, reviewed and adapted from materials provided by General Plastics Manufacturing.

For more information on this source, please visit General Plastics Manufacturing.

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