Aircraft Materials and Hardware - Term Paper Example

? Aircraft Materials and Hardware Table of Content Topic Page Aim 2 Introduction 2 Pure aluminum and Aluminum alloys 3 Heat treatment process of aluminum alloys- Solution and precipitation heat treatment 3 Steel 4 Procedure - Carburizing & Nitriding 4 Composite Materials 5 Fiber Reinforced Materials 7 Laminated Structures 7 Plastic 8 Rivets 9 Summary/Conclusion 11 Aircraft Materials and Hardware Aim Awareness and comprehension of the usages, strengths, restrictions, and other features of structural metals is important to suitably make and retain aircraft structures, particularly airframes. In building aircraft and in maintenance and overhaul, a minor nonconformity from design requirement, or the replacement of substandard materials, might cause in the loss of both lives and aircraft. The usage of inappropriate materials can expunge the best workmanship. The choice of the right material for a particular overhaul job stresses understanding of the common physical and chemical properties of different metals. Another aspect of aircraft maintenance and repair is that aircraft hardware is frequently ignored since of the insignificant size of the parts. But, selection of right hardware for the use in aircraft is very vital for the efficient operation and safety of any aircraft. The goal of this essay is to emphasize the importance of material, its various process and hardware selection for the use in aircraft structures (faa.gov, ND). Introduction The earlier aircraft materials must refer timber as the first materials used to create a power-driven aircraft. The Wright brothers involved mainly of Sitka spruce and bamboo fastened and bolted together to make a canvas-covered assembly. Aircraft made by wooden material were very successful in the initial years of flying. Currently, timber is only fit for fairly small aircraft. As the requirement for larger aircraft became unavoidable for the modern society, materials with superior specific strength come to be essential. Currently airplane consists mainly of aluminum alloys with steel, titanium alloys and polymer compounds. The equilibrium of materials does rest on on the kind of airplane as military fighter airplanes have much higher amounts of composites and titanium alloys. In this essay more emphasize is given to aircraft materials and its different processes. Pure aluminum and Aluminum alloys Airplane must be made of material with lesser weight to carry more loads and to reduce fuel consumption. The more travelers an airplane can transport the more income an aircraft corporation can create. At the same time as pure aluminum have less weight, very good corrosion resistance and exceptional thermal and electrical conductivity but it is weak and ductile to be used on aircraft structure in its pure form. The credit goes to Dr. Alfred Wilma, a German metallurgist, who found out that aluminum alloyed with copper and heat treated properly can be made much sturdier. The alloy of aluminum with 4% copper is said to be Duralumin and the heat treatment procedure is termed as precipitation hardening. After this Duralumin have characteristically little specific gravity and great strength (450 MPa). Since it is restricted to a maximum amenity temperature of around 660°C supplementary heat treatable aluminum alloys have been developed for aircraft use. These comprise a variety of intricate aluminum-zinc alloys which improve the maximum strength of several aluminum alloys. These alloys have used for contemporary aircraft design in which the skin of the fuselage and wings are stressed aluminum alloy parts that lessen the total heaviness of the aircraft. The disadvantage of the aluminum alloys discussed above have a drawback of not being as corrosion resistant as compared to pure aluminum. Therefore a thin coating of pure aluminum is usually fused to either sides of the alloy and is called Alclad aluminum alloy. Even though titanium is very costly it is used where great strength is required in load bearing applications for example, landing gear and engine escalating supports (student, 1999). Heat treatment process of aluminum alloys- Solution and precipitation heat treatment Two methods of heat treatments are pertinent to aluminum alloys. The solution heat treatment and the others are called as precipitation or artificial ageing. Many aluminum alloys, for example 2017 and 2024, improve their full properties because of solution heat treatment followed by about 4 days of aging at room temperature. Some alloys, for instance 2014 and 7075, need both solution heat treatment and precipitation. The heat treatment for hardening aluminum alloys involves four separate processes such as heating to a predetermined temperature, soaking at temperature for a definite length of time and swiftly quenching to a fairly low temperature. These three steps are considered as solution heat treatment for aluminum alloys. The temperatures for solution heat treatment differ with dissimilar alloys and vary from 825 °F to 980 °F with maximum tolerance. The aluminum alloys are in a relatively soft state sooner after solution treatment. To gain their maximum strengths, they must be either naturally aged or precipitation hardened. Through this hardening and strengthening process, precipitation of the soluble constituents from the supersaturated solid solution occurs. Precipitation hardening develops a excessive rise in the strength and hardness of the material with analogous decreases in the ductile properties. This procedure used to attain the preferred growth in strength is referred as aging, or precipitation heat treatment(faa.gov, ND). Steel Steel is made use in places where strength is required in limited areas, for instance in the under carriageways. Alloy steels can be heat treated to offer most mechanical properties and occupy a smaller amount volume that is vital, since there is less free space. It is used cautiously although it is weighty and augmented fragility at the low temperatures at higher altitudes. Lithium is as well used as an alloying component for better properties. Procedure - Carburizing & Nitriding Carburizing is a casehardening method where carbon is supplemented to the exterior of low carbon steel to obtain high surface hardness. Hence carburized steel has a high carbon content exterior and a low carbon interior. During this process the surface is hardened whereas the core continues to stay soft and tough. Common procedure of carburizing is called pack carburizing. In this process the steel parts are filled in a vessel with charcoal or other material rich in carbon. The vessel is then closed with fire clay, placed in a furnace, heated at 1,700 °F, and soaked at that temperature for specified hours. When the vessel temperature rises, carbon monoxide fume fills within the vessel and, combines with the gamma iron in the exterior of the steel. The gravity of the carbon penetrates rest on on the period of soaking. There are other techniques of carburizing, for example gas carburizing and liquid carburizing. Alloy steels having less carbon content in addition to low carbon steels can be carburized by any of the three procedures. Nitriding is also a case hardening procedure to obtain desired high hardness on the surface of the part. Dissimilar to other casehardening procedures, formerly the parts are heat treated to attain certain physical properties. So, the parts are hardened and tempered before nitriding process. During this process parts are positioned in a nitriding furnace and heated to a temperature of around 1,000 °F and at this temperature, ammonia fume is disseminated within the specifically built furnace cavity. Because of the high temperature the ammonia vapor get parted into nitrogen and hydrogen. The nitrogen reacts with the iron to form nitride. The iron nitride is spread in small particles at the exterior of parts and penetrates inward. The depth of diffusion rests on the span of the process. The soaking periods of nitriding is usually 72 hours to produce the preferred depth of case. Nitriding can be done with least of distortion, since of the low temperature used for the process and no quenching is necessary after exposure to the ammonia fume (avstop.com, 2012) Composite Materials Specific strength is one of the properties that are considered suitable for choosing materials for aircraft use. Contemporary airplanes are tremendously capable and fast flying. The developments in materials knowledge accounts for the inexpensive and lessening in weight whereas speed determined by improvement of the airplane's contour and its engines. Progresses in polymer compounds are creating them progressively more widespread. They have attributed low mass and great mechanical properties. Composites contain of fibers of glass, carbon, Kevlar or boron strengthened in an epoxy resin matrix. They are substituting some of the aluminum alloys in commercial airplane and superior applications in military aircraft, for example, the Eurofighter (student, 1999). The airplane engineering initiated to improve artificial fibers to enhance airplane design in the year 1940. Composite materials have been in use since that time. Composites began in aeronautics, however at the present are being used by many other manufacturing industries, comprising auto racing, sporting goods, and boating, in addition to defense industries. A composite material is explained as a combination of diverse materials. This description is so broad that it can denote to metal alloys made-up of a number of dissimilar metals to augment the strength, ductility, conductivity otherwise whatsoever features are preferred. Similarly, the composition of composite materials is a mixture for strengthening, for example a fiber, particle, enclosed and prepared by a resin, making a structure. Independently, the reinforcement and the resin are dissimilar from their joint state. Even in their joint state, they can still be separately branded and mechanically detached. For example, composite concrete is a blend of cement (resin) and gravel or strengthening rods for the reinforcement to make the concrete. Several benefits for using composite materials are: high strength to weight ratio, fiber-to-fiber transfer of strain permitted by chemical bonding, stiffness to density ratio 3.5 to 5 times more than steel or aluminum, longer life than metals, greater corrosion resistance, tensile strength 4 to 6 times more than steel or aluminum, better design flexibility, glued structure avoid joints and fasteners and without difficulty maintainable. The drawbacks of composites comprise: inspection approaches tough to carryout, lack of long term design database, comparatively fresh technology devices, cost, costly processing apparatus, shortages of standardized system, variation of materials, processes, and techniques, absence of repair information and expertise, products usually poisonous and perilous and insufficient reliable procedure for manufacture and maintenances. The augmented strength and the ability to design for the performance requirements of the product, composites are much superior to the old-style materials used in today’s airplane. Since increasingly composites are used, the costs, design, inspection comfort, and evidence of strength to weight compensations will aid composites turn out to be the material of ideal for airplane assembly. Fiber Reinforced Materials The objective of strengthening in reinforced plastics is to deliver maximum strength. The three key forms of fiber reinforcements are particles, whiskers, and fibers. The particle is a square piece of material. Glass bubbles are hollow glass spheres, and then their sizes are identical on all sides and they are termed a particle. A whisker is a portion of material that is lengthier than it is width. Whiskers are typically solo crystals. They are very sturdy and used to strengthen ceramics and metals. Fibers are only filaments that are lengthier than they are wide. Fibers can be prepared from nearly any material, and are not crystalline structure like whiskers. Fibers are the base for most of composites. Fibers are slighter than the human hair and are generally laced into cloth-like materials. Laminated Structures Composites can be prepared with or without an inside core of material. Covered structure with a core center is considered as sandwich structure. Laminate creation is robust and rigid, however it is heavy. The sandwich laminate is identical in strength, and its weight is considerably less; less weight is vital for aerospace products. Numerous kinds of cores for laminated structures comprise rigid foam, wood, metal, or the aircraft industry choice of honeycomb made from paper, carbon, fiberglass or metal. It is vital to monitor proper methods to construct or overhaul laminated structures to guarantee the strength is not compromised. A sandwich assembly is prepared by taking a high-density laminate and back plate and sandwiching a core in the center. The choice of materials for the face and back plate are determined by the design engineer, subject to the planned application of the part. It is imperative to follow companies’ maintenance specification directives concerning testing and repair processes as applicable to a specific airplane. Sandwich-type laminates are made of two or more solid sheet facings or a formed shape enfolding a fiberglass honeycomb or foam-type core. Honeycomb cores are prepared of glass cloths impregnated with polyester or a mixture of nylon and phenolic resins. The specific density and cell size of honeycomb cores differs over substantial latitude. Honeycomb cores are usually made-up in blocks that are cut to the required dimension (faa.gov, ND). Plastic Materials may be categorized in several methods; however they can as well be categorized based on the behaviors in which they react to temperature. Certain polymers go through an enduring chemical response when heated. Others merely go through a temporary physical transformation. However a strong knowledge of why different polymers respond to temperature will assist to make worthy choices when selecting polymer materials. Transparent plastic materials utilized in aircraft canopies; windshields, windows and where alike transparent enclosures. Plastics are categorized according to their response to heat: thermoplastic and thermosetting. The thermoplastic material softens after heating and it becomes fluid as heat increases. This condition permits it to be injected with force from a heated chamber into a cool mold. After cooling the thermoplastic will take the shape of the mold, however there is no chemical curing at work. The transformation observed with the thermoplastics is only physical change and if reheated the same is rescindable. Hence thermoplastic material can be recycled many times, however repeated reprocessing will ultimately damage the polymer (rlhudson.com). Thermosetting plastics strengthen when heated, and reheating has no softening effect. Thermosetting plastics cannot be reformed after being completely cured. Besides, transparent plastics are made in two methods: monolithic and laminated. Laminated transparent plastics are prepared from transparent plastic sheets glued by an inner layer material, typically polyvinyl butyric. For the reason that of its shatter resilient potentials, laminated plastic is superior to solid plastics and is utilized in several pressurized airplane. Usually most of the transparent sheet used in aircraft industry is manufactured in agreement with several military aircraft specifications. Contemporary progress in transparent plastics is stretched acrylic. Stretched acrylic is a kind of plastic that before being formed it is drawn in both directions to reorganize its molecular arrangement. These acrylic sheets have a superior resistance to impact and are a lesser amount of effect to shatter and its chemical resistance is better (faa.gov, ND). Rivets Sheets of metal need to be secured together to form the airplane assembly, and this is typically done with solid aluminum alloy rivets. A rivet is a metal pin with a shaped head on one end once the rivet is produced. The shaft of the rivet is introduced into a bored hole, and its shaft is then distorted by a hammer or pneumatic device. The head shaped by hammer or by pneumatic device, is named as shop head. The shop head role is same as a nut on a bolt. Furthermore to their use for joining aircraft skin units, rivets are likewise used for joining spar segments, for holding rib units in place, for safeguarding fittings to several parts of the airplane, and for joining numerous bracing parts and other parts together. The rivet makes a joint which is as strong as the material being linked. The material used for the maximum number of airplane is solid shaft rivets is aluminum alloy. The strength and temper settings of aluminum alloy rivets are recognized by digits and letters alike to those accepted for the ID of strength and temper settings of aluminum and aluminum alloy standard. The 1100, 2017?T, 2024-T, 2117-T, and 5056 rivets are the five grades typically available. The 1100 rivet, which is contains 99.45 percent pure aluminum, is very soft and it is used for riveting the softer aluminum alloys, such as 1100, 3003, and 5052. The 2117-T rivet is used largely for riveting aluminum alloy structures because of it is ready for use, as received and requires no additional heat treatment. It as well has an extraordinary resistance to corrosion. The 2017-T and 2024-T rivets are used in aluminum alloy assemblies where additional strength is required than is attainable with the same size 2217-T rivet. Metal temper is a vital feature in the riveting procedure, particularly with aluminum alloy rivets. Aluminum alloy rivets have the same heat-treating characteristics as aluminum alloy stock. The rivet must or reasonably soft, once a good head can be shaped. The 2017-T and 2024-T rivets are annealed before riveting. They harden with age.These rivets are recognized as ice box rivets since these rivets are annealed, and essential to be kept refrigerated till they are to be used. The 2017-T rivet must be used within around 1 hour and the 2024-T rivet within 10 to 20 minutes after taken out from cooling. The 5056 rivet is made use for riveting magnesium alloy assemblies since of its corrosion-resistant potentials in blend with magnesium. Mild steel rivets are made use for riveting steel assemblies. The procedure of annealing rivets is identical as that for stock. For this purpose an electric air furnace, a salt bath furnace, or a hot oil bath is required. The temperature range is from 625 °F to 950 °F. They are quenched in cold water directly after process. The 2017-T and 2024-T rivets, begin to age harden immediately after being put to the room temperature. Hence, they need to be used directly after quenching or kept in cold storage (faa.gov, ND). Summary/Conclusion In the above essay the discussion was about the aircraft material and its various processes. Awareness and comprehension of the usages, strengths, restrictions, and other features of structural metals is important to suitably make and retain aircraft structures, particularly airframes. The earlier aircraft materials must refer timber as the first materials used to create a power-driven aircraft. Airplane must be made of material with lesser weight to carry more loads and to reduce fuel consumption. Dr. Alfred Wilma, a German metallurgist, who found out that aluminum alloyed with copper and heat treated properly can be made much sturdier. Two methods of heat treatments are pertinent to aluminum alloys. The solution heat treatment and the others are called as precipitation or artificial ageing. Steel is made use in places where strength is required in limited areas, for instance in the under carriageways. Carburizing is a casehardening method where carbon is supplemented to the exterior of low carbon steel to obtain high surface hardness. Nitriding is also a case hardening procedure to obtain desired high hardness on the surface of the part. Dissimilar to other casehardening procedures, formerly the parts are heat treated to attain certain physical properties. Specific strength is one of the properties that are considered suitable for choosing materials for aircraft use. A composite material is explained as a combination of diverse materials. Composites can be prepared with or without an inside core of material. Composite materials are widely used in modern aircraft industry. The thermoplastic material softens after heating and it becomes fluid as heat increases. The transformation observed with the thermoplastics is only physical change and if reheated the same is rescindable. Thermosetting plastics strengthen when heated, and reheating has no softening effect. Thermosetting plastics cannot be reformed after being completely cured. The material used for the maximum number of airplane is solid shaft rivets is aluminum alloy. The strength and temper settings of aluminum alloy rivets are recognized by digits and letters alike to those accepted for the ID of strength and temper settings of aluminum and aluminum alloy standard. Aluminum alloy rivets have the same heat-treating characteristics as aluminum alloy stock. In conclusion the discussion regarding aircraft materials and various processes were short and brief. More discussion and research is needed to explore more details of various other procedures for aircraft materials. References avstop.com, (2012). Casehardening. AvStop Online Magazine [On line] Available from: [05 december 2012] faa.gov. (ND). Aircraft Metals Processes &Hardware, Chapter 5 [On line] Available from: [05 december 2012] rlhudson.com (2011). Thermoset VS. THERMOPLASTIC MATERIALS, Hudson Techfiles [On line] Available from: [05 december 2012] Student, (1999). Aluminium and its alloys used in aircraft NSW HSC [On line] Available from:< http://hsc.csu.edu.au/engineering_studies/focus/aero/2580/aluminium_alloys.html> [05 december 2012] 1 Read More