Material Analysis of Aircraft Wing Skin essay

To ensure and guarantee the safety of flight, the materials in an aircraft used is an important element. This includes small parts like nuts, bolts and screw. The materials are chosen because they must have a certain features like light and extremely strong This project looks into the parts of an airplane mainly the wing. The wing of an aircraft comprises of skin, spar, ribs and stringer. We will further discuss into the properties, test standards and factors of the materials being chose for each part of the wing.

However the materials used differ depending on the models and the company that produces it, therefore we set up Boeing 37-700 as our model. Various resources including journals, books and even websites were used as our reference. The possibility of changing the materials currently used for something better in terms of cost and materials are also studied. The economic aspect will also be focused on such as the cost, availability and the effect on product regarding the selection.

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By studying the properties of aircraft, we are looking to enhance our engineering skills predominantly on engineering materials as well as to adapt ourselves in the world of aviation industry. MAIN AIRCRAFT WINGS – SPAR In a fixed-wing aircraft, the spar is often the main structural member of the wing, running span wise at right angles to the fuselage. The spar carries flight loads and the weight of the wings while on the ground. Hence, In order to do the materials for a wing spar needs to be very strong and highly elastic.

For the Boeing 737, the spars of the wings are made up of aluminum alloy 7178 which mainly consists of aluminum, zinc, magnesium, chromium & copper composites. In this section, we will briefly descriptor the aluminum 71 78 properties, its test standard, reasons why this material are chosen to make his part of the wing spar and suggestion of new material to substitute the current material. Properties Needed For A Wing Spar. 1. Can withstand great load factors. 2.

Highly elastic in order to avoid cracks during vibration when the aircraft flying through strong winds. 3. High strength in bending stress. Aluminum Alloy 7178 CHEMICAL COMPOSITION PHYSICAL properties Element Content (%) Properties Metric Aluminum, AY 88. 1 Density 2. 82 g/cam Zinc, Zen 6. 8 Melting Point CHIC Magnesium, MGM 2. 7 THERMAL PROPERTIES Copper, Cue 2. 0 Thermal Expansion 23. 410-6/C) Chromium, Cry 0. 26 477 co -CHIC Table 1: Table of chemical composition, physical properties and thermal properties for Alloy 7178.

MECHANICAL PROPERTIES Hardness, Knops gaff;mm-2 Ultimate Tensile Strength mamma Tensile Yield Strength 538 Amp Compressive Yield Strength mamma Modulus Of Elasticity 71. Gap Fatigue Strength mamma Incapability Table 2: Mechanical properties of Aluminum Alloy 71 78 Discussion: Factor Which Influence In The Selection Of Aluminum Alloy 7178 For Producing Main Wing Spar The main wing spar has to withstand the upward bending heavy loads resulting from the wing lift force, downward forces bending loads while on rounds, drag loads, rolling inertia loads and etc.

In order to withstand all of the forces acting on the main wing spar, the material for the spar must be very strong, hard, flexible (to withstand the vibration when flying against strong winds), and very incapability in order to ease the production of the main spar at a low cost. Based on a few researches, Boeing Company engineer really make the right decision to use Aluminum Alloy 7178 as the main wing spar material. This alloy satisfies the minimum requirement to make a main wing spar for a commercial airbus which one of the heaviest flying aircraft in the world.

Based on the properties in Figure 3, the Alloy 7178 is a high strength alloy that has high ultimate tensile strength, compressive yield strength and tensile yield strength which can solve the problems in overcoming the enormous stress from all the forces acting upon the main wing spar. From Table 3, we also infer that alloy 7178 has a very elastic property with high modulus of elasticity. This can reduce the risk of the main spar wing to crack or break due to constant vibration during flights.

Due to the high fatigue strength the alloy 7178 has, a longer durability of the main spar can be ensure. The alloy 7178 is very economical because its incapability percentage is quite high. This can make it easier to ready the material with lower cost and power in a short time. This alloy is available in almost every material supplier companies around the globe. It also can be buy online. Plus, the market price for this material is around US $ 2,000 – 4,500 / Ton which very reasonable in exchange for producing high quality spar in order to ensure the safety of the aircraft.

Possibility Of Using New Material In Making Of Main Wing Spar Based on some researches, there are many type of materials can replace aluminum alloy 7178. One of it is carbon fiber-reinforce polymer (CPRM) which has the upper hand against alloy 71 78 in quality aspect. The Cuffs have high strength-to-weight ratio, rigidity, very light in weight and not to mention its ultra-high tensile strength. Despite of the advantages, CPRM still can’t be used widely due to its very expensive market price. Hence, this will increase the cost of the production of the aircraft main wing tenfold which is not very economical.

Therefore, many research still need to be done in order to reduce the cost of the CPRM and widen the usage of the material in commercial aircraft. Test Standard For Aluminum Alloy 7178 Fatigue Test When a material (aluminum alloy 7178) is applied loads repeatedly, it undergoes a weakening process and it is called fatigue. This test examines how the structure of the aircraft responds to standard operational service over a long period of time. Different stages of its operation are covered such as landing, take-off and taxiing. Therefore these conditions have to be recreated.

This kind oftenest puts the aircrafts structure to its limit and verifies that the aircraft covers its designed life span. Our research on fatigue test focuses on flutter test. The flutter which also called as vibration test, it is to study the aluminum structural behavior under aerodynamic disturbance throughout the flight. It is significant as aircrafts encounter natural vibration during operation and to demonstrate that the spar is adequately damped. Flutter calculations are normally based on equations which represent the overall balance of forces occurring in the interaction oft or more natural modes of vibration.

The tests were made with two half-span rectangular spars of aspect ratio 4 in an intermittent type supersonic wind tunnel at Mach numbers of 1; 6 and 2′ O. Wind speed and density are fixed in a tunnel during an experiment meant that subsonic procedure in which wind speed is adjusted to produce flutter could not be followed. The spars were then mounted on a pitching axle in the tunnel wall and the wing pitching stiffness reduced until flutter occurred. Comparative calculations were then made for each test configuration using arbitrary modes, based on the resonance characteristics of the wings, and theoretical derivatives.

The calculated and experimental critical stiffness and frequencies are in reasonable agreement. MAIN AIRCRAFT WINGS – STRINGERS & RIBS Stringers Stringer is a thin strip of material to which the skin of the aircraft is fastened. In the fuselage, stringers are attached to formers (also called frames) and run in the longitudinal direction of the aircraft. They are primarily responsible for transferring the aerodynamic loads acting on the skin onto the frames and formers. In the wings or horizontal stabilizer, stringers run span wise and attach between the ribs.

Its primary function also is to transfer the bending loads acting on the wings onto the ribs and spar. Rib In aircraft construction, ribs are forming elements of the structure of a wing specially in traditional construction. By analogy with the anatomical definition of “rib”, the ribs attach to the main spar, and by being repeated at frequent intervals, form a skeletal shape for the wing. Usually ribs incorporate the airfoil shape of the wing, and the skin adopts this shape when stretched over the ribs.

Materials Commonly used 1) Aluminum-2024-TO 2) Ala minimum-lord-Molybdenum-Zirconium 3) Aluminum Alloy 7075 Properties Needed For Both Stringers And Ribs 1) High tensile strength 2) Strength 3) High elongation 4) Light in Weight 5) High corrosion resistant The Most Quality Materials CHEMICAL PROPERTIES MATERIAL PROPERTIES Aluminum (AY) 87. 2 to 91. 4 % 2. 80 (175 lb/oft) Zinc (Zen) 5. 1 TTT. 1% Elastic (Young, Tensile) Modulus 72 Gap (10 x 106 SSI) Magnesium (MGM) 2. 1 to 2. 9% Fatigue Strength (Endurance Limit) 160 Amp (23 x 103 SSI) Copper (Cue) 1. 2 to 2. 0% Melting Onset (Solidus) 477 CO(891 OF) Iron (Fee) O to 0. % Specific Heat Capacity 960 J/keg-K Silicon (Is) O to 0. 4 % Strength to Weight Ratio 211 ink-m/keg Manganese (M n) O to 0. 30 % Electrical Conductivity 33 % Chromium (Cry) 0. 18 to 0. 28 % Elongation at Break 11% Zirconium (Ezra) o to 0. 25 % Shear Strength 331 Amp (48 x 103 SSI) Titanium (It) O to 0. 2 % Tensile Strength: Ultimate (LIT S) 590 Amp (86 x 103 SSI) Aluminum alloy 7075 TO for both stringers and ribs. Discussion: Reasons Why TO Temper 7075 Is Selected In Building BIBB-700 Stringers And Ribs TO temper 7075 has an ultimate tensile strength of SSI (510-572 Amp) and Yield strength of at least SSI (434-?503 Amp).

It has a failure elongation of 5-1 1 The TO temper is usually achieved by honeymooning the cast 7075 at CHIC for several hours, and then aging at CHIC for 24 hours. This yields the peak strength of the 7075 alloy. The strength is derived mainly from finely dispersed eat and eat’ recipients both within grains and along the grain. Aluminum in its purest form is too soft and reactive to be of structural use. However, its alloys, such as 7075 aluminum alloy, make it structurally stronger and more useful in the manufacturing of durable products. 075 aluminum is a cold-wrought alloy and the strongest of the aluminum alloys, or as strong as some lower-grade steel products, but it is lighter in weight. The principal alloying ingredients of 7075 aluminum are zinc and copper. Its other metallic elements include magnesium, iron, silicon, manganese, chromium and titanium, in descending order by quantity. Aluminum alloy 7075 is high availability in market. Some of companies that supply aluminum alloy 7075 are Tannin Baggie Metal Products Co, Ltd. , Tannin TEED Gangue Trade Co, Ltd. ND Tannin Yeti Steel Sales Co. , Ltd.. Today, we also can easily get the aluminum alloy 7075 material via online order. There are a lot of online suppliers. Some of them are aerodynamic metals pet Ltd. And Shanghai Changing Metal Product Co,Ltd, Test standard For Aluminum Alloy 7075 Tensile Test The tensile test is the most commonly test used method to measure the mechanical properties of aluminum alloys which in this case is alloy 7075. This test is used to determine the ultimate tensile strength, compressive yield strength and tensile yield strength of the alloy.

All of this data can be obtained by measuring the load required to extend specimen or measuring the respective extension. First of all, cut the alloy 7075 into the shape like in Figure 11. Next, measure the load required to extend the specimen and measure the total extension of the gauge length due to only within the gauge length will deformation be uniform. The output of the test is usually a load vs. extension plot but they are not very useful for comparing tests because the results depend on the alloy 075 dimensions.

Hence, the plot is converted to a plot of stress vs. strain in order for the experiment to be independent of specimen dimensions. MAIN AIRCRAFT WINGS – WING SKIN Wing is the most vital part compared to other parts in an airplane. This is because the part provides lifting force required for an airplane to ascend to higher altitude. The design of the wings varied depends on the type of aircraft. However, most airplanes have the same components which are skin, spar, ribs, and stringers. In flight, the force of the air acts against the skin.

The primary function of the wing skin is to form an impermeable surface to purport the aerodynamic pressure distribution which provides lifting capability. From the skin, this aerodynamic force is transmitted to the ribs and then to the spars. Resistance to shear and torsion’s loads is supplied by shear stresses developed in skin and spars while axial and bending loads are reacted by action of skin and stringers. Material Selection Criteria for Wing Skin The wing skin needs to be thin to resist shear and tensile loads efficiently. The wing skin also needs to have high strength to withstand high surface pressure.

This can be achieved by thicken the skin. Besides, it should be light weight. This can be achieved by thinning the skin. In consideration of lightning strike, the material should be able to conduct electrical and has a high heat resistant to keep heat below ignition point at fuel tank area. Another main criteria is high stress corrosion resistance to have a long life. Materials Used Currently Aluminum honeycomb Fiberglass and aluminum faced honeycomb Aluminum Alloys Characteristic Have high strength in room temperature but decreases if the temperature is high.

Extremely flexible and lightweight as it is one third of steel weight. Compared with other metals, aluminum has a relatively large coefficient of inner expansion. Aluminum is an excellent conductor of heat and electricity. An aluminum conductor weighs approximately half as much as a copper conductor having the same conductivity. Aluminum reacts with the oxygen in the air to form an extremely thin layer of oxide. Though it is only some hundredths of a (my)m thick (1 (my)m is one thousandth of a millimeter), this layer is dense and provides excellent corrosion protection. The layer is self- repairing if damaged.

Aluminum alloy is easily obtained and is being used widely in aviation industry around the world. CHEMICAL PROPERTIES 2. 86 g/cam 7. 6 to 8. % Tensile Yield strength 85 SSI 1. 8 to 2. 3 % Compressive yield strength 88 SSI 2. 0 to 2. 6 % Elongation % 0. 15 Max Fracture toughness 32. 6 SSI 0. 10 Max Tensile Strength: Ultimate (OUTS) 91 SSI 0. 05 Max 0. 04 Max 0. 08 to 0. 25 % 0. 06 Max In consideration of the criteria of the materials, aluminum alloy is the best compared to the others. For airplane, the aluminum is alloyed together with copper, magnesium, manganese, silicon and iron.

There are many types of aluminum alloy with different composition to obtain the best Of its properties. Currently, the wing skin is made up of aluminum alloy 7178 for he upper part and aluminum alloy 7055 for the lower part. Table 4: Properties of aluminum alloy 7055 Application Of Aluminum Alloy 7055 Alloy 7055-15TH and T 76511 tempers are targeted for the replacement of 7075-16TH 1 and 71 78-16TH 1 alloy tempers, respectively, as well as other applications that require high tensile and compressive strengths and need excellent exfoliation corrosion and SEC resistance, such as upper wing structures, keel beams and longer.

This alloy had been replacing the upper part of wing skin and may be replacing other parts too. Other applications include seat tracks, cargo tracks, fuselage frames and fuselage triggers. Advantages Of Aluminum Alloy 7055 Compared To Aluminum Alloy 71 78 Improve toughness, strength and stress corrosion resistance compared aluminum alloy 7178. This alloy also has an extended service life as it corrodes slightly over time. Furthermore, aluminum alloy 7055 reduces cost as it is cheaper and has extensive life span.

Aluminum alloy 7055 costs a minimum of 1000 USED per metric ton while aluminum alloy 71 78 costs around 2000 USED per metric ton. Corrosion Resistance Test There are two methods used for determining the corrosion resistance of a material namely salt spray test and immersion test. ) Salt Spray Test The salt spray test is a standardized test method used to determine corrosion resistance of coated samples. Salt spray test is an accelerated corrosion test that produces a corrosive attack to the coated samples in order to predict its suitability in use as a protective layer.

The appearance of corrosion products (oxides) is evaluated after a period of time. The more corrosion resistant is the longer the period in testing without showing signs of corrosion. Salt spray testing is popular because it is cheap, quick, well standardized, and reasonably repeatable. There is, however, only a weak correlation teens the duration in salt spray test and the expected life of a coating since corrosion is a very complicated process and can be influenced by many external factors.

Nevertheless, salt spray test is widely used in the industrial sector for the evaluation of corrosion resistance of finished surfaces or parts. Testing Equipment The apparatus for testing consists of a closed testing chamber, where a salt water solution (usually, a solution of 5% sodium chloride by weight, dissolved in water) is atomized by means of spray nozzle(s).