Application Of Titanium Alloys And Ceramics Matrix Composites In Aerospace Engineering

Literature Review

Advanced Materials are those that are as a result of modification of existing materials. The resulting ‘new material’ is of superior quality. The purpose of the modification is to come up with a material of high quality whose characteristics are fundamental to the application in a given sector (Majaja, n.d.).  Categories of advanced materials include superconductors, high performance alloys, energy materials, composites and auxetic materials.

Advanced materials are applicable in many fields such as aerospace engineering, car manufacturing and medical engineering. For the purpose of this report, I shall consider the application of Titanium Alloys and Ceramic matrix composites in the field of aerospace engineering especially aircraft manufacture. Planes and rockets and all other technology that may be required to fly in aerospace are required to be light, strong and tough. Therefore, for a material to be fit for use in the aerospace sector, it has to have the following characteristics depend on what part it meant to manufacture;

1. Low Density.
2. High Temperature Strength.
3. Fatigue Resistance.
4. Hot Corrosion Resistance.

From previous studies, both Titanium alloys and Ceramic matrix composites exhibit some of the characteristics listed above hence may be considered to be used in the manufacture of parts to be used in aerospace technology such as air engines.  We shall analyze their properties, composition and suitability to be used in the manufacture of parts.

Aerospace engineering revolves around the concept, design and manufacture of aircrafts and spacecrafts. Different types of materials have been used over time for aerospace purposes. In the first stages of development and manufacture of airplanes, timber was widely used to fabricate the wings of aircrafts. With continued research and development in the aerospace field, more suitable materials were developed including use of metal. Today, materials used in the manufacture of parts to be used in aircrafts or spacecrafts are of high quality and are used to build certain parts depending on the requirements. Advanced materials that are able to achieve a certain targeted property such as low density, durability or strength have been developed for use in the manufacture of aircraft parts such as wings and engines.

1. Titanium And Titanium Alloys

Titanium is a chemical transitional element with a metallic lustre, silver in colour . It has a low density a high strength. It has  low thermal and electrical conductivity, non-toxic, excellent resistance to fracture, bio-acceptability and good ductility (Froes, 2015). Titanium is also corrosion resistant when exposed to saline conditions Metals that are obtained as a result of the combination of titanium and other chemical elements are known as Titanium alloys. Chemical elements such as molybdenum, aluminum, vanadium and iron to produce alloys of low density but high strength. The elements that are alloyed with titanium have varied effects on the properties of titanium. Tin, iron, aluminum and vanadium have shown to increase the ultimate tensile strength and the tensile yield strength but reduce ductility and toughness. Titanium alloys are particularly important because they are used in the manufacture of aerospace parts such as jet engines. Titanium alloys are also applicable in other fields such as military, medical prostheses, dental implants and many others.  

Titanium Alloys

Of all metallic elements known to man, none has a higher strength to density ratio than titanium up to 550^oC (Bhatnagar & Srivatsan, 2009). This property coupled with high resistance to corrosion makes titanium and its alloys the ideal material to be used in the aerospace field. The most common tanium alloys that are used in aerospace technology  Ti 6Al-4V (Grade 5) which is used in the manufacture of aircraft turbines, engines and other structural parts. This alloy is preferred due to its high resistance to corrosion, low density and high strength all which are an ideal requirement for any material to be used in the manufacture of aircrafts. Below is a brief description of specific areas of aerospace application

1. Helicopters- Titanium alloys are used in the highly stressed parts including the rotor head.
2. Aircraft fuselages- Due to the lightweight nature if the titanium alloys, they are preferred in the manufacture of aircraft fuselages. The Alloys have also been used to stop the growth of fatigue cracks in fuselages. This is done by applying the titanium alloy in thin, narrow rings around the fuselage. This ensures that potential cracks do not propagate to the surface of the aircraft.
3. Space related application- The pay load of space vehicle is significantly small hence the need to save on weight for the aircrafts. Titanium and its alloys were used in the first Apollo and mercury programs(Bhatnagar & Srivatsan, 2009).
4. Air frames of aircrafts
5. Manufacture of aircraft Engines- “The figure below shows examples of titanium alloy applications for the V2500 engine employed by Airbus A320. The V2500 engine is manufactured by International Aero Engines, an international joint venture that includes Japanese enterprises.Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo-0.1Si alloys are most commonly used for the manufacture of aircraft engines” (Ikuhiro, et al., 2014).

Conventional structural ceramics such as silicon nitrade alumina have one weakness i.e. they are highly susceptible to cracking when mechaninal load is applied on them. This has resulted in the development of ceramic composites so as to try and overcome these weaknesses.

Ceramic matrix composites are considered a new class of ceramic material and are obtained from the embedment of carbon or ceramic fibres into the ceramic matrix. The resultant material is called Ceramic Fibre Reinforced Ceramic. The bonding forces between the fibre and the matrix is very low hence the composite hence the interface is weak. This combined with the porosity of the matrix is important because it results to a low strain to failure compared with the that of pure ceramic. Also, the composite has a low density. All these make the composite to have a mass specific property that is incomparable to that of any other structural material beyond 1000^oC (Krenkel, 2008). Introduction of fibre in the matrix has also improved the cracking resistance capabilities of the ceramic. Ceramic composites have also proven to have a higher resistance to thermal shock and elongation compared to the pure ceramics.

Ceramics matrix composites are being used in place of ceramics as they overcome the weaknesses of the pure ceramic such as brittleness. The composites have a high resistance to corrosion, can withstand high temperatures, and they are lightweigh (Narottam & Jacques, 2015)t. This properties make them ideal for use in the aerospace industry. The following are some of the areas in the aerospace field where their application has been of immense contribution to improving the quality, efficiency and reliability of the concern parts.

1. Jet engines- According to general electric, use of ceramic composites reduces the weight of the engine as they are lighter resulting to reduction in the centrifugal force in the engine which will lead to design of smaller engine shafts(Kellner, 2016).
2. Heat shield for space vehicles- Temperatures in the heat shield may rise up to 1500^o With temperatures this high, many structural materials would lose their integrity. Ceramic matrix composites can withstand this temperature and still remain structurally stable and ensure resistance to thermal shocks.

1. Titanium And Titanium Alloys

The main body of an aircraft is referred to as the aircraft fuselage. The fuselage is considered the third in importance after the wing and tail. This is the part that holds the crew, passengers and cargo i.e. the cockpit, cabin compartments for passengers and cargo (Sadraey, 2013). One of the requirements for a material to be used to manufacture the airframe is that it must be ductile. This ensures a faster process of fabricating the required shape. Other important qualities that are considered when determining the suitability of a material to be used in aircraft manufacture are conductivity(electrical and thermal), density, toughness, hardness, malleability, elasticity contraction, expansion, and fusibility and others (Federal Aviation Authority, n.d.). The fuselage is the largest part of an aircraft body hence the material used for its construction should be lightweight but strong so as to control the final weight of the resulting product. As stated previously, titanium has a high strength to density ratio hence it make titanium and its alloys the most suitable candidates for the manufacture of the airframes and fuselages. Other alternative materials that may be considered for the use in airframes are aluminium and aluminium alloys. Aluminium is a chemical element with a metallic lustre and in its purest is white in colour. It is ductile and malleable and offers the highest resistance to corrosion. Alloys of aluminium are mainly from the combination with silicon, manganese, chromium and magnesium. Aluminium is lightweight and corrosion resistant hence can be considered in the making of airframes. However, compared to titanium, it has a lower strength value. Aluminium is cheaper compare to titanium and it has the best corrosion resistance.

Ceramics Matrix Composites

The aircraft engine is that part that propels an aircraft by generating mechanical power. In a commercial jet engine, air enters through the front and compressed. The compressed air is forced to enter the combustion chamber. In the chamber, fuel is then sprayed onto the compressed air then ignited. As a result of the combustion, gases are produced and then released at the back of the engine. As the gasses escape with pressure on the back, they produce a thrust that propels the aircraft forward. A large amount of air is sucked into the engine at a rate of 1.2 tons per second. The combustion of air and fuel results into burning temperatures of up to 2000^oC. The material that is to be used in the manufacture of the engine require to accommodate high temperatures and pressure. The preferred material should be tough, hot corrosion resistance, lightweight, fatigue resistance and high temperature strength. Titanium and its alloys can satisfy those requirements. Even at high temperatures, titanium remains structurally stable and is highly resistant to corrosion. This make it the ideal candidate for use in jet engines.

1. Ceramix Matrix Composites

A heat shield is a structure designed to protect other parts from external heat by absorbing, dissipating or reflecting it. Spacecraft enter the atmosphere of planets at very high speeds and depend upon air resistance to slow them down. The resulting friction leads to aerodynamic heating which can lead to the part or whole of the spacecraft. This implies that spacecrafts have to be protected from these very large temperatures. Heat shields are provided for this reason. Ceramic matrix components are have low density, are resistant to corrosion and thermal shock resistance. Ceramic matrix components used in the heat shield can withstand the resulting temperatures (close to 1500^oC) and still remain structurally intact. Alternative materials that cn be used in the heat shield include copper and aluminium. Copper is often used to make heat shields for terrestrial purposes. The main disadvantage in using copper is that it is not as light as aluminium or titanium. Copper is preferred to aluminium because it ealisy joins to copper and stainless steel (Seely, et al., 2011).

Bhatnagar, N. & Srivatsan, T. S. eds., 2009. Processing and Fabrication of Advanced Materials -XVII. New Delhi: I.K. International Publishing House Pvt. Ltd..

Federal Aviation Authority, n.d. [Online] Available at: ttps://www.faa.gov/regulations_policies/handbooks_manuals/aircraft/amt_handbook/media/FAA-8083-30_Ch05.pdf[Accessed 19 October 2017].

Froes, F. H. ed., 2015. Titanium: Physical Metallurgy, Processing and Applications. Materials Park(Ohio): ASM-International.

Ikuhiro, I., Yoshihisa, S., Tsutomu, T. & Nozumu, A., 2014. Application and Features of Titanium for the Aerospace industry. [Online]
Available at: https://www.nssmc.com/en/tech/report/nssmc/pdf/106-05.pdf[Accessed 19 October 2017].

Joshi, V. A., 2006. Titanium Alloys: An Atlas of Structures and FractureS. London: Taylor & Francis.

Kellner, T., 2016. General Electric Reports. [Online] Available at: https://www.ge.com/reports/space-age-cmcs-aviations-new-cup-of-tea/[Accessed 19 0ctober 2017].

Krenkel, W., ed., 2008. Ceramic Matrix Composites: Fibre Reinforced Ceramics and their Applications. Weinheim: WILEY-VCH Verlag GmbH & Co. KGaA.

Majaja, N., n.d. The Department of Trate and Industry Repuplic of South Africa. [Online] Available at: https://www.thedti.gov.za/industrial_development/Advanced_Materials.jsp[Accessed 18 10 2017].

Narottam, P. B. & Jacques, L. eds., 2015. Ceramix Matrix Composites; Materials, Modelling and Technology. Hoboken(New Jersy): John Willey & Sons.

Sadraey, M. H., 2013. Aircraft Design: A systems Engineering Approach. West Sussex: John Wiley & Sons Ltd..

Seely, M. L., Bonnema, E. C. & Conningham, E. K., 2011. Meyer Tools & Mfg. Inc. [Online] Available at: https://www.mtm-inc.com/ac-20110627-heat-shields-materials-and-cost-considerations.html[Accessed 19 October 2017].

The Atlas Group, n.d. The Atlas Group. [Online] Available at: https://theatlasgroup.biz/latest-materials-used-aircraft-manufacturing/
[Accessed 18 October 2017].

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