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September 5, 2017

Exotic Materials: How Amazing Metals Make Aviation Possible

Weight is money in aviation. Heavier airliners take more fuel to get from point A to point B. When you consider the fact that an average Boeing 777 in a 30-year lifetime will fly:

  1. 3,500 hours a year
  2. At an average speed of 500 miles per hour
  3. For a total of 30 x 3500 x 500 = 52,500,000 miles, or roughly the distance to Mars

That’s a lot of fuel! By volume, 50% of the aerospace materials market consists of the same garden variety metal you use to wrap up your dinner leftovers: aluminum. That’s because aluminum is lightweight and strong. But that’s not the whole story. The other 50% is made up of exotic materials like carbon fiber reinforced polymers and beryllium that allow airplanes to travel faster, farther and longer without refueling.

Exotic Materials, Their Properties and Uses in Aviation

Density

In aerospace design, the density of the material used is critical to maintaining the balance and weight distributions of the aircraft. The specified weight of a material per cubic inch is the preferred method of measurement because it can determine the weight of a part before it is actually manufactured. Titanium has an excellent strength-to-density ratio, which explains why Titanium bolts are commonly used in aircraft landing gears. Carbon fiber reinforced polymers also have an amazing strength-to-density ratio, which explains why they are replacing aluminum for both structural and component applications in aerospace. Use of carbon fiber can reduce an airliner’s weight by 20%. The Airbus A350 XWB’s sweeping wingtips, which are made of carbon fiber, deliver roughly 5% in fuel savings. 50% of the airframe of the Boeing 787 Dreamliner, which you can see being constructed in the video above, is made of carbon fiber.

Strength

Strength measures a material’s ability to resist deformation or breaking from stress. Chrome-molybdenum steel, which is steel made of a small percentage of molybdenum and chromium, is stronger than carbon steel but it remains highly ductile and malleable. For that reason it has virtually replaced carbon steel in landing gears, engine mounts, and fuselage tubing. Inconel bolts, made of Inconel 718, retain a 220ksi (kilopound per square inch) tensile strength even at temperatures of 900 degrees Fahrenheit.

Hardness

Related to strength, harness is the measure of a metal’s ability to withstand cutting, abrasion, penetration, or permanent distortion. Certain aluminum alloys popular in aviation are hardened like steel with heat treatment. Chromium steel is high in hardness and strength, which makes it ideal for use as the balls and rollers of antifriction bearings, as well as in H11 tool steel bolts, which have excellent resistance to stress, impact, gross cracking and thermal fatigue cracking.

Elasticity

Elasticity is the property that allows a metal to return to its original shape and size when the force that causes the change is removed. Obviously this is an incredibly important quality in aerospace manufacturing, as you wouldn’t want parts to be permanently distorted after an applied load is removed. Each metal has an elastic limit, beyond which a force will cause permanent distortion. Nickel is a common element used to increase a steel’s elastic limit, tensile strength, and hardness. Nickel steels containing between 3 to 3.75 percent nickel are used extensively for aircraft parts, such as aerospace bolts, pins, clevises, keys and terminals.

Ductility

Ductile metals are essential to aviation. Ductility refers to a metal’s ability to be permanently twisted, bent or drawn into different shapes without breaking. Ductile metals are found in many areas of an airplane because of their resistance to failure even under extreme shock loads. Aluminum alloys are both lightweight and very ductile, making them idea for use in the fuselage, as wing skin, and for ribs, spars, bulkheads and other extruded parts.

Malleability

Similar to ductility, malleability refers to a metal’s ability to be pressed, rolled or hammered into particular shapes without breaking or cracking. Copper is an example of a malleable and ductile metal, which is why it is most commonly used in wiring. In aerospace, copper and copper alloys are essential to electrical systems and instrument tubing. Bronze, a copper alloy containing tin, is used for tube fittings in aircraft. Copper aluminum alloys, called aluminum bronzes, are among the most common in aircraft, and are used in air pumps, gears, diaphragms, and condenser bolts.

Conductivity

Conductivity is the property that enables a metal to carry electricity or heat. Heat conductivity is important in aviation because of its important role in determines how much heat is necessary to weld two metals together. When designing an aircraft, it’s important to know different metals’ electrical conductivity in order to eliminate radio interference.

Thermal Expansion

Referring to the contraction and expansion of metals as a result of heating or cooling. A metal’s thermal expansion is an especially important consideration when designing castings, welding jigs, and when working with hot rolled material. Waspaloy, a truly exotic material, is a nickel-based superalloy that contains everything from cobalt and chromium to titanium. It is uniquely reliable at high temperatures, making Waspaloy bolts ideal for the hottest areas of an aircraft: as turbine blades, shafts, rings, seals and turbine disks.

Toughness and Brittleness

One of the most desirable qualities of aircraft metal, toughness determines how much a metal can be stretched or deformed without breaking. Brittleness, on the other hand, is a metal’s ability to withstand deformation and bending without shattering. Hardened steels, cast aluminum and cast iron are all examples of very brittle metals that are not suitable for structural applications on an aircraft.

See What We Create at Aerospace Manufacturing

Aerospace Manufacturing uses exotic materials to create high strength, close tolerance aerospace fasteners that meet the expectations of clients ranging from the U.S. Navy and Lockheed Martin to Sikorsky and NASA. Check out our homepage to learn more!