Magic Material of Aviation, Space and Defence Vehicles; Boron

Boron is one of the most widely used elements on our planet, it can also be included in the group of metals. Did you know that boron has uses in very specific fields besides its general industrial applications? For example; aerospace and defence sectors have been using boron for decades due to its ability to be doped with other elements and its high contribution to the creation of hybrid or composite materials. 

What is boron and what does it do?

Boron has a primary use in chemical compounds. About half of global production is used as a glass fibre additive for insulation and structural materials. The next group of uses are high-strength, lightweight and heat-resistant polymer and ceramic composites, where boron is included as a reinforcing material to increase their mechanical properties and heat resistance.

What makes boron different from other materials?

The boron atom can form a range of materials and alloys that are important for projects in the aerospace industries. The element tends to form borides with other metals, particularly aluminium, titanium and copper, due to their similar boiling points. This valuable property contributes to the formation of solid materials resistant to corrosion or oxidation resulting from exposure to various types of media.

The structural properties of boron make it difficult for different elements (especially oxygen) to pass through its chemical bonds, which means that boron-reinforced metal will not rust over time and will retain its strength even when exposed to extreme conditions such as extreme temperatures (from -200C to 1000C). For example, boron is added to many jet engine components so that these engine parts are both resistant to extreme temperatures and do not become brittle.

Boron can be doped with many elements to achieve various properties. For example, by mixing Boron with Aluminium, you can create a material that has the conductivity of Copper but does not corrode in salt water like Iron or Steel.

Another way in which Boron makes aerospace and defence applications so advantageous is that it can withstand extreme temperatures without melting or becoming brittle, and is an excellent conductor of electricity at low cost. Because of these unique qualities, it typically comes into play when designing aircraft parts, as it outperforms most metals over time and also creates less interference in electrical systems.

Its stability even allows it to be used extensively in ships, as it will withstand steel structures exposed to salt water for years without showing any signs of corrosion.

The growing importance of Boron Carbide, a Boron derivative, in the aerospace industry

Today, carbide is used in three main sectors: aerospace and defence, electrical energy storage devices (e.g. batteries) and high temperature ceramics. The growing importance of boron carbide in the aerospace industry is based on its ability to withstand extreme temperatures, with a melting point of over 5600 degrees centigrade, and its excellent resistance to corrosion from molten salts present at various levels inside jet engines during the take-off phase.

The properties that make boron carbides attractive for use as an alloying agent are chemical inertness at high temperatures or exposure to gases such as hydrogen fluoride, low coefficient of thermal expansion, etc.

Global demand for Boron Carbide is expected to grow due to its many critical uses in the defence sector, including research and development of more effective bulletproof vests. Ongoing developments in the defence sector will increase its consumption in all geographies, as it has been determined that Boron Carbide can be used in the development of military tanks and to increase the bulletproof properties of body armour.

A significant number of developments in human and vehicle protection technology, systems that require better protective systems such as ballistic warheads and armoured vehicles made of different materials, and the extreme need to find new ways to protect soldiers from bullets are constantly increasing the demand for boron carbide.

The Birth of Boron Fibre, another Boron derivative, has been called the most important breakthrough in materials in the last 3000 years

In January 1969, the US Navy and Air Force contracted Grumman (F-14) and McDonnell Douglas (F-15) to design the F-14 and F-15 aircraft, respectively. Both aircraft designs required the use of a robust, high modulus fibre composite material in the structural construction of the aircraft to reduce vibration and minimise the weight of each aircraft.

The revolutionary material on the horizon was carbon fibre; however, its mass production was very difficult and limited. There were not enough suppliers to meet the needs of aircraft designers, so the search for and development of another material was turned to the discovery and development of Boron Fibre, whose fibres have an excellent balance between strength and weight. 

Grumman decided that this lightweight yet strong type of fibre would be perfect for the horizontal stabiliser surfaces of the F-14 Tomcat. The use of Boron composites in the construction of the F-14 Tomcat reduced the aircraft's structural weight by 19%, and the service life of Boron composites was 2.5 times that of other metals.

Materials used in the structural construction of the F-14 Tomcat.

In contrast, McDonnell Douglas chose to use boron fibre as the active structural composite material for the F-15's fuselage skin and vertical wing rudders, as well as for the fuselage panels (covers) and vertical stabilator (vertical wing) surface. The use of boron fibre composites resulted in a 22% weight saving on the F-15 Eagle.

Materials used in the structural construction of the F-15 Eagle.

High-performance Boron Fibre made history when it was first used in the F-14 and F-15 aircraft. Due to its creativity and functions; US aerospace scientists have called boron fibre the most important invention in materials in the last 3,000 years.

A few other examples of the use of Boron Additive Composite Materials in Air Vehicles:

Predator Gray Eagle

The high compressive strength of the Boron-doped composite material used in the aircraft allowed the aircraft's load carrying capacity to be increased. 

Predator's Gray Eagle variant.

SH-60

SH-60 

Boron-epoxy composites are used in the rotor blades of the SH-60 Helicopter.

B-1B 

Boron-Epoxy composite material is used in horizontal and vertical stabilisers and wing slats. The high compressive strength and stiffness of Boron provided reduced weight in the stabilisers.

B-1B Lancer

Did you know that there is no alternative material to Boron fibre composite materials for the construction of the relevant structural parts of air and space vehicles that require high specific compressive strength or high stability under cyclic thermal loading?

Application in Space Structures

Many new application areas have emerged for boron fibre in the structural components of space shuttles, space stations and satellites. Boron fibre, the only fibre with a positive coefficient of thermal expansion, is hybridised with high modulus graphite fibres to produce composite structures with high stiffness.

Another Boron variant, Boron Nitride; The Future of Aerospace?

Boron Nitride (BN) is a material developed for use in high temperature applications. 

Boron Nitride has very good thermal conductivity, making it suitable for heat dissipation in electronic components. Boron Nitride also has a high dielectric constant, making it an excellent choice for circuit boards that require insulation between circuits and is excellent for use as an insulator.

In addition to these properties, Boron Nitride ceramics are strong enough to withstand extreme temperatures up to 2000°C, exhibit a low coefficient of thermal expansion, and thanks to its long-term durability, can be used repeatedly without breaking down or spilling material into the environment.

The versatility of its application areas points to the potential use of Boron Nitride in future aircraft and spacecraft. Due to their untapped potential, governments are conducting extensive research on new Boron Carbide variants in order to advance in technology and improve their existing technologies.