The aerospace industry has grown in leaps since the first aircraft by the Wright brothers. The main characteristic of aerospace materials is that they should be highly resistant to heat, lightweight and anti corrosive. The conditions in space, or at high altitudes produce excessive heat since the airplane, drone or rocket will need to travel at excessively high speeds. High speeds create intense friction leading to excessive heat.
The material therefore has to be extremely resistant to heat, as well as have a high capacity to dissipate this heat. This is especially crucial for aerospace materials that go at very high altitudes, meaning they experience extremes in temperature from extreme cold due to speed, and extreme cold as it passes through cold levels of the atmosphere.
This article examines the different aerospace material specifications as well as the future of aerospace materials. With changes in technology different alloys have been developed to improve the natural characteristics of the various metals and compositions so far used in aerospace materials.
Titanium as an Aerospace Material
Titanium is one of the most popular materials in aerospace materials and technologies. Titanium has either been used as pure titanium or as titanium alloys for the various parts in airplanes and rockets. It is lightweight with a density of about 60% of steel, and this makes it ideal for low fuel aircraft, and space shuttles. Titanium is also highly resistant to corrosion, is extremely strong and has great heat resistance.
Another advantage of titanium is that it is highly compatible with carbon fiber reinforced plastic (CFRP). It is worth to note that CFRP is fast growing as a aerospace material due to its lightweight and cheap cost. Carbon fiber is also readily available making it ideal for the development of the aerospace industry in low income economies.
Therefore, the compatibility of titanium and CFRP has led to low fuel consumption aircraft and drones and with most commercial aircraft increasing use of CFRP, it is likely that titanium will overthrow stainless steel as the most preferred aerospace material.
Titanium Use in Airframes and Engines
Turbo fan engines are commonly used in aircraft, and certain parts are made using titanium alloys. Pure titanium is heavier and doesn’t have the corrosion resistance, nor crack propagation resistance that titanium alloys and other materials such as CRFP have. The fan and the compressor are the main parts of the engines that typically use titanium based alloys, since these parts require the titanium with high CRFP compatibility to ensure there is sufficient fracture toughness and crack propagation resistance required.
Due to titanium’s lightweight composition, it is the best material for use in airframes. Previously, in areas where extra high strength is required stainless steel and other steel-based alloys and materials were used for the frames and joints. However, lately, pure titanium and titanium based alloys have been used to reduce weight while retaining the same strength and durability associated with stainless steel.
There is a high potential for galvanic corrosion, due to the presence of heterogenous materials, and therefore, most aircraft manufacturers are using titanium in virtually all areas of the airframe. This not only reduces the risk of galvanic corrosion, but also the risk of strain resulting from coefficient difference in how the different materials expand due to heat.
The development of titanium alloys with CRFP characteristics has largely reduced these risks.
Use of Stainless Steel as An Aerospace Material
Stainless steel has been a main component of aerospace material for its strength to weight ratio. For this reason, it is the best material for use in some structural components such as the brackets and the fittings. These components undergo immense strain and due to their small size as compared to the rest of the structure, they require higher tensile strength. Stainless steel is ideal since it is highly anticorrosive and resistant to heat.
Aircraft exhaust systems need to be composed of materials that are extremely resistant to high temperatures as well as have the capacity to retain their structural and material integrity at high pressures. Stainless steel offers the best combination of materials that can offer the best composite material for exhaust systems as well as fuel tanks. Stainless steel’s highly anti-corrosive properties can withstand intense pressures necessary in transportation and storage of combustible fuels.
Lastly, stainless steel offers the best heat shields for spacecrafts. Stainless steel has a high temperature resistance that can withstand the high friction at high speeds in rockets. The high temperature generated as the rocket is is taking off and also during re-entry can melt most metals and material composites. For this reason, stainless steel is used for the entire surface of the rocket since combining different materials would lead to warping.
Other Materials Used in Aerospace
Composites, carbon fiber reinforced plastics and nickel have lately emerged as material composites in aerospace engineering. Each of these materials have certain benefits that the others lack. CFRP is considered one of the best composite materials when combined with other metals. It is most compatible with titanium and this composition offers a better alternative to pure aluminum and even stainless steel. Since aircraft require different materials, the compatibility of these materials is crucial.
On the other hand, nickel is preferred for its heat resistance and capacity to conduct electricity well. Space environment requires material that can withstand high radiation and other electromagnetic waves, whilst retaining structural integrity. Nickel alloys offer a great alternative to stainless steel and titanium for smaller components.
In conclusion, the choice of aerospace material relies on the material’s unique characteristics in handling the special environments in aerospace travel. Whether the use is in commercial aircraft or in space travel, utmost consideration has to be made when selecting the right metal or composite to use.
More expensive composites are available but these are for use in specialized missions. Manufacturers also need to consider future availability of raw materials, scalability and cost and manufacturing constraints. Furthermore, the environmental impact of developing these materials is a crucial factor.
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