PRE-TEST Module 4 The Materials Units 1-2-3 points · 1Complete the missing parts of this diagram referring to the general classification of aircraft materials. (13 p.) PRE-TEST Module

Complete the missing parts of this diagram referring to the general classification of aircraft materials. (13 p.)1

PRE-TEST Module 4 The Materials Units 1-2-3 ..../60 points

Find the right follow-ups of the following definitions(1-7) referring to the properties of materials (a-g).Write the letter in the space provided. (7 p.)

1.Hardness refers to the ability of a metal to resistabrasion, penetration, cutting action, or permanentdistortion. Hardness may be increased by working themetal and, in the case of steel and certain titanium andaluminum alloys, by heat treatment and cold-working.……

2.Brittleness is the property of a metal that allows verylittle bending or deformation without shatteringoccurring. In other words, a brittle metal is apt tobreak or crack without change of shape. ……

3.A metal that can be hammered, rolled, or pressed intovarious shapes without cracking or breaking or otherdetrimental effects is said to be malleable. ……

4.Ductility is the property of a metal that permits it tobe permanently drawn, bent, or twisted into various

2 shapes without breaking. This property is essential formetals used in making wire and tubing. Ductile metalsare greatly preferred for aircraft use because they areeasy to form and for their resistance to failure undershock loads. ……

5.Elasticity is the property that enables a metal to returnto its original shape when the force that causes thechange of shape is removed. ……

6.A material that possesses toughness will withstandtearing or shearing and may be stretched or otherwisedeformed without breaking. ……

7.Conductivity is the property that enables a metal tocarry heat or electricity. The heat conductivity of ametal is especially important in welding, because itgoverns the amount of heat that will be required forproper fusion. Conductivity of the metal, to a certainextent, determines the type of jig to be used to controlexpansion and contraction. ……

AIRCRAFT MATERIALS

............................. Metal

Acrylic ......................: Fibres:

• epoxy • glass

• ..................

• graphite

• ..................

...........................

...........................

............................. Advancedcomposites

..........................................

Non-Ferrous

Metals

e.g. aluminum e.g. silicon carbide

.............................

.............................

Steel

.........................................

e.g. chrome-molybdenum

............................. Alloys ofaluminum

e.g. ...........................

............................. Titanium

Thermoplasticresins

a. This property is necessary in sheet metal that is to beworked into curved shapes such as cowlings, fairings,and wing tips. Copper is one example of a metal withsuch characteristics.

b. This property is a desirable one in aircraft metals.c. In aircraft, the electrical one must also be considered in

conjunction with bonding, which is used to eliminateradio interference. Metals vary in their capacity toconvey heat. Copper, for instance, has a relatively highrate of this property, both thermal and electrical.

d. For this reason, aluminum alloys are used for cowlrings, fuselage and wing skin, and formed or extrudedparts, such as ribs, spars, and bulkheads. Chrome-molybdenum steel is also easily formed into desiredshapes. This property is similar to malleability.

e. Because structural metals are often subjected to shockloads, this property is not a very desirable one. Castiron, cast aluminum, and very hard steel are all metalswhich have this property.

f. Structural parts are often formed from metals in theirsoft state and are then heat treated to harden them sothat the finished shape will be retained. This propertyand strength are closely associated properties of allmetals.

g. This property is extremely valuable, because it wouldbe highly undesirable to have a part permanentlydistorted after an applied load have been removed.

Fill in the blanks choosing from the following words.(20 p.)

advanced – aviation – Avional – boron – carbon – ceramic –chrome – cobalt – employed – Ergal – ferrous – GLARE –matrix – metals – smart – stiffer – stresses – superalloys –temperatures – titanium

Structural materials can be classified into (1) .................................

and composites. The former can be catalogued into(2) .................................. metals and non-ferrous metals; the latterinto polymer-matrix composites, metal-matrix compositesand (3) ..................................-matrix composites.The main ferrous metals used in (4) .................................. are:steel and its alloys, of which the most used one is(5) ..................................-molybdenum.

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The main non-ferrous metals are aluminum, magnesiumand (6) ................................... . The main aluminum alloys arealloy 2024 – or (7) .................................. – and alloy 7075 – or(8) .................................. . Beside these, there are aluminum-lithium alloys which are (9) ...................... and less densethan conventional aluminum alloys.(10) .............................. are high-strength alloys, resistant to hightemperatures and severe mechanical (11) .............................. .They can be combined with nickel, (12) .................................. andiron. Composites can be classified into three categories accordingto the (13) .................................. material: polymer, metal, orceramic. The most common fibers used with polymer-matrices are: glass, (14) .................................., carbon and aramid.Anyway, for higher (15) .................................. metal-matrix andceramic-matrix composites are (16) .................................. .Finally, there is a series of other (17) ...............................

materials, such as carbon- (18) .................................. composites,fiber metal laminates – e.g. ARALL and (19) ..................................

– and the latest technological discovery: (20) ..................................

materials.

Answer the following questions. (20 p.)

1. What is strength?........................................................................................................................

2. What is plasticity?........................................................................................................................

3. What is meant by ferrous and non-ferrous metals?........................................................................................................................

4. What are Avional and Ergal?........................................................................................................................

5. Where is titanium employed?........................................................................................................................

6. What is a composite?........................................................................................................................

7. What does it consist of?........................................................................................................................

8. What are the main fibers used with epoxies? ........................................................................................................................

9. What are the main advanced materials?........................................................................................................................

10. What is meant by “smart materials”?........................................................................................................................

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PRE-TEST Module 4 The Materials Units 1-2-3

IN-DEPTH ANALYSIS TEXTS

Composites and advanced materials in aircraft

For many years, aircraft designers proposed theoretical designs that they could not build because the materials needed toconstruct them did not exist. For instance, large space-planes, like the Space Shuttle would have proven extremely difficult,if not impossible, to build without heat-resistant ceramic tiles to protect them during re-entry. And high-speed forward-swept-wing airplanes like Grumman’s experimental X-29 or the Russian Sukhoi Su-27 Berkut would not have beenpossible without the development of composite materials to keep their wings from bending out of shape.Composites are the most important materials to be adapted for aviation since the use of aluminium in the 1920s.Composites are materials that are combinations of two or more organic or inorganic components. One material servesas a ‘matrix’, which is the material that holds everything together, while the other material serves as a reinforcement, inthe form of fibres embedded in the matrix. Until recently, the most common matrix materials were ‘thermosetting’materials such as epoxy, bismaleimide, or polyimide. The reinforcing materials can be glass fibre, boron fibre, carbonfibre, or other more unusual mixtures.Fiberglass is the most common composite material, and consists of glass fibres embedded in a resin matrix. Fiberglasswas first used widely in the 1950s for boats and automobiles, and today most cars have fiberglass bumpers covering a steelframe. Fiberglass was first used in the Boeing 707 passenger jet in the 1950s, where it comprised about 2% of the structure.By the 1960s, other composite materials became available, in particular boron fibre and graphite, embedded in epoxyresins. The US Air Force and US Navy began research into using these materials for aircraft control surfaces like aileronsand rudders. The first major military production use of boron fiber was for the horizontal stabilizers on the Navy’s F-14Tomcat interceptor. By 1981, the British Aerospace-McDonnell Douglas AV-8B Harrier flew with over 25% of its structuremade of composite materials.The greatest value of composite materials is that they can be both lightweight and strong. The heavier an aircraft weighs,the more fuel it burns, so reducing weight is important to aeronautical engineers.Despite their strength and low weight, composites have not been a miraculous solution for aircraft structures. Compositesare hard to inspect for flaws (defects). Some of them absorb moisture. Most importantly, they can be expensive, primarilybecause they are labour intensive and often require complex and expensive fabrication machines. Aluminum, by contrast,is easy to manufacture and repair. Anyone who has ever gotten into a minor car accident has learned that dented metalcan be hammered back into shape, but a crunched fiberglass bumper has to be completely replaced. The same is true formany composite materials used in aviation.Modern airliners use significant amounts of composites to achieve lighter weight. About 10% of the structural weightof the Boeing 777, for instance, is composite material. Modern military aircraft, such as the F-22 (Fig. 1), use compositesfor at least one third of their structures, and some experts have predicted that future military aircraft will be more thantwo-thirds composite materials. But for now, military aircraft use substantially greater percentages of composite materials

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Something more about… THE MATERIALS

Module 4

Fig. 1The Lockheed F-22 uses compositesfor at least a third of its structure.

than commercial passenger aircraft, primarily because of the different ways in which commercial and military aircraft aremaintained.Aluminum is a very tolerant material and can take a great deal of punishment before it fails. It can be dented or puncturedand still hold together. Composites are not like this. If they are damaged, they require immediate repair, which is difficultand expensive. An airplane made entirely from aluminum can be repaired almost anywhere. This is not the case forcomposite materials, particularly as they use different and more exotic materials. Because of this, composites will probablyalways be used more in military aircraft, which are constantly being maintained, than in commercial aircraft, which areobliged to require less maintenance.Thermoplastics are replacing thermosets as the matrix material for composites. They hold much promise for aviationapplications. One of their big advantages is that they are easy to produce. They are also more durable and tougher thanthermosets, particularly for light impacts, such as when a wrench drops on a wing accidentally. The wrench could easilycrack a thermoset material but would bounce off a thermoplastic composite material.In addition to composites, other advanced materials are under development for aviation. During the 1980s, many aircraftdesigners became enthusiastic about ceramics, which seemed particularly promising for lightweight jet engines, becausethey could tolerate hotter temperatures than conventional metals. But their brittleness and difficulty to manufacture weremajor drawbacks, and research on ceramics for many aviation applications decreased by the 1990s.

Aluminum still remains a remarkably useful material for aircraft structures and metallurgists have worked hard to developbetter aluminum alloys (a mixture of aluminum and other materials). In particular, aluminum-lithium is the mostsuccessful of these alloys. It is approximately 10% lighter than standard aluminum. Beginning in the later 1990s it was usedfor the Space Shuttle’s large external tank in order to reduce weight and enable the shuttle to carry more payload. Itsadoption by commercial aircraft manufacturers has been slower, however, due to the high cost of lithium and the greaterdifficulty of using aluminum-lithium (in particular, it requires much care during welding). But it is likely that aluminum-lithium will eventually become a widely used material for both commercial and military aircraft.

Module 4 The Materials

Fig. 2Many modern light aircraft areconstructed in composite materialsuch as this Glasair.

Composite materials in aircraft

Smart materials: lighter, stronger aircraftSmart materials, which are able to radically change their shape on application of an electric field, represent an emergingleading edge technology that is being developed in the South West of England. Through a partnership between aircraftmanufacturer Airbus UK Ltd and the Universities of Bath, Bristol and Exeter, a radical change in the way aircraft wingsare built is being developed which aims to significantly reduce the cost of flying. Currently, the large changes in wingprofile necessary during take-off landing and high-altitude flight are generated by complex hydraulic systems within anaircraft’s wing. This may not be the best way to proceed in future aircraft design, however, as smart materials could provideinteractive shape changes much more efficiently. Without such large hydraulic systems or turbulent airflow overinterrupted wing surfaces, significant weight reduction and improved aerodynamics are just two of the advantages ofusing smart materials as part of aircraft wing design. Specially designed carbon-fibre wing segments can be changed intodifferent preset configurations, to mimic or improve upon the wing profiles of current designs, by applying a voltage topiezoelectric actuators embedded in these structures. Using smart materials in wing design could therefore yield realeconomic and environmental benefits by reducing weight and drag and thus eventual fuel burn and CO

2emissions.

LINKS

� http://www.tpub.com/air/1-18.htm (Properties of materials)

� http://www.tpub.com/content/aviation/14018/ (Aircraft construction and materials)

� http://planet.rv-groovin.com:5555/fundamaterials.htm (Aircraft materials)

� http://www.ube.com/content.php?pageid=137 (Aerospace materials)

VIDEOS

� YouTube � Aircraft materials � Lightweight materials of the future

� YouTube � Aircraft materials � Composite materials

� YouTube � Aircraft materials � Smart materials: visions of future flying

� http://www.azom.com/materials-video-details.asp?VidID=316 (Aluminium forging helps Ferrari win double titles)

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Module 4 The Materials

Fin boxand rudder Fin/fuselage fairing

Alleron

Spoiler shroudtop panels

Flap track fairings

Inner air brakes

DoorsTailplane and elevator

Apron Bay top panel

Flaps

Spoilers

Accesspanels anddeflectors

Access panels

Pylon fairings

Enginecowls

Leg fairings

Floor panels

Belly fairing skins

DoorsRadome

Carbon fibre reinforced plastic

Aramid fibre reinforced plastic

Glass fibre reinforced plastic

(Courtesy of Professional Engineering)

Fig. 3List of composite parts in the mainstructure of an airliner.