Advanced Engineering Advanced Engineering materialsmaterials

Types of MaterialsTypes of Materials

MetalsMetals High densityHigh density Medium to Medium to

high melting high melting pointpoint

Medium to Medium to high elastic high elastic modulusmodulus

ReactiveReactive DuctileDuctile

CeramicsCeramics• Low densityLow density• High melting High melting

pointpoint• Very high Very high

elastic elastic modulusmodulus

• UnreactiveUnreactive• BrittleBrittle

PolymersPolymers• Very low Very low

densitydensity• Low melting Low melting

pointpoint• Low elastic Low elastic

modulusmodulus• Very Very

reactivereactive• Ductile and Ductile and

brittle typesbrittle types

OrganicsOrganics(wood, paper, textiles)(wood, paper, textiles)

• SustainableSustainable• RecyclableRecyclable• BiodegradableBiodegradable• Easily workedEasily worked• FlammableFlammable• Share properties Share properties

of compositesof composites

Metals and AlloysMetals and Alloys

Metals are the most common of the elements.Metals are the most common of the elements.

Strong, with good conductivity for electricity Strong, with good conductivity for electricity and heat. Mostly easily worked.and heat. Mostly easily worked.

BronzeBronze for spearheads and axesfor spearheads and axes SteelSteel Aluminium, MagnesiumAluminium, Magnesium Titanium: as strong as steel but 45% lighterTitanium: as strong as steel but 45% lighter Shape memory alloysShape memory alloys

PolymersPolymers

Flexible Thermoplastic (PE, PU)

Rigid Thermoplastic (PVC, PS)

Rigid Thermosets (EP, PF)

Elastomers or rubbers

CeramicsCeramics

A ceramic is a A ceramic is a composite composite consisting of consisting of hard granules hard granules bound together bound together by a ‘glue’ by a ‘glue’ often like often like glass.glass.

Examples:Examples:StoneStone

Limestone (CaCOLimestone (CaCO33))

Sandstone (SiOSandstone (SiO22))

Granite (aluminosilicates)Granite (aluminosilicates)

Cement and ConcreteCement and ConcreteMixtures of lime (CaO), Mixtures of lime (CaO), silica (SiOsilica (SiO22) and ) and alumina (Alalumina (Al22OO33) )

The CaO reacts with water The CaO reacts with water and carbon dioxide from the air and carbon dioxide from the air to form Cato form Ca22COCO3 3 (limestone)(limestone)

Microstructure of ceramicsMicrostructure of ceramics

Engineering ceramic – Al2O3Pottery ceramic

Properties of ceramicsProperties of ceramics Extremely hard and resistant to wearExtremely hard and resistant to wear Very high melting pointVery high melting point Resistant to chemical attackResistant to chemical attack High compressive strengthHigh compressive strength Low and variable tensile strengthLow and variable tensile strength Low density ( as compared to steel)Low density ( as compared to steel) Ceramic components are not easy to make Ceramic components are not easy to make

because of their high mp and hard/brittle because of their high mp and hard/brittle so can’t be machined.so can’t be machined.

Organic materialsOrganic materials

Have been used since the stone age eg Have been used since the stone age eg wood or bone handle for stone axe.wood or bone handle for stone axe.

Fibre for ropesFibre for ropes Sinew for bow stringSinew for bow string Timber for houses and furnitureTimber for houses and furniture Paper and cardboard for packagingPaper and cardboard for packaging Composites e.g. srbp for electrical Composites e.g. srbp for electrical

componentscomponents Glues and varnishesGlues and varnishes

WoodWood

Has a grain structure with Has a grain structure with directionally oriented fibersdirectionally oriented fibers

High compressive strengthHigh compressive strength Good tensile strength along grain axisGood tensile strength along grain axis Weak across grainWeak across grain Prone to decay and infestation eg Prone to decay and infestation eg

woodworm – however look at timber woodworm – however look at timber used for staithes at Dunstonused for staithes at Dunston

CompositesComposites

In its most basic form In its most basic form a composite material a composite material is one which is is one which is composed of at least composed of at least two elements working two elements working together to produce together to produce material properties material properties that are different to that are different to the properties of the properties of those elements on those elements on their own. their own.

The properties of a The properties of a material depend on material depend on the kind of stress it is the kind of stress it is exposed to. For exposed to. For example concrete has example concrete has a good compressive a good compressive strength, but a low strength, but a low tensile strength. This tensile strength. This is overcome by is overcome by reinforcing with steel reinforcing with steel rods - making a rods - making a composite.composite.

Types of stressTypes of stress

Tension Compression

Shear Flexion

Tensile strength and tensile Tensile strength and tensile modulusmodulus

Tensile strength Tensile modulus (stiffness)

Three main groups of Three main groups of engineering compositesengineering composites

Polymer matrix compositesPolymer matrix composites

Metal matrix compositesMetal matrix composites

Ceramic matrix compositesCeramic matrix composites

Polymer matrix compositesPolymer matrix composites

These are the most common These are the most common composites in use today. Also known composites in use today. Also known as FRP - Fibre Reinforced Polymers (or as FRP - Fibre Reinforced Polymers (or Plastics) these materials use a Plastics) these materials use a polymer-based resin as the matrix, and polymer-based resin as the matrix, and a variety of fibers such as glass, a variety of fibers such as glass, carbon and Aramid (Kevlar) as the carbon and Aramid (Kevlar) as the reinforcement.reinforcement.

PMC Bulk materialPMC Bulk material

Resin systems such as epoxies and Resin systems such as epoxies and polyesters have limited use for the polyesters have limited use for the manufacture of structures on their own, manufacture of structures on their own, since their mechanical properties are not since their mechanical properties are not very high when compared to, for example, very high when compared to, for example, most metals. However, they have other most metals. However, they have other desirable properties for engineering, desirable properties for engineering, particularly their ability to be easily formed particularly their ability to be easily formed into complex shapes.into complex shapes.

ReinforcementReinforcementMaterials such as glass, aramid (kevlar), carbon and Materials such as glass, aramid (kevlar), carbon and

boron have extremely high tensile and compressive boron have extremely high tensile and compressive

strength but in ‘solid form’ these properties are not strength but in ‘solid form’ these properties are not

readily apparent. This is due to the fact that when readily apparent. This is due to the fact that when

stressed, random surface flaws will cause each material stressed, random surface flaws will cause each material

to crack and fail well below its theoretical breaking to crack and fail well below its theoretical breaking

point. To overcome this problem, the material is point. To overcome this problem, the material is

produced in fiber form, so that, although the same produced in fiber form, so that, although the same

number of random flaws will occur, they will be number of random flaws will occur, they will be

restricted to a small number of fibers with the remainder restricted to a small number of fibers with the remainder

exhibiting the material’s theoretical strength.exhibiting the material’s theoretical strength.

Crack propagation in bulk Crack propagation in bulk reinforcement materialreinforcement material

Crack propagation in fiber Crack propagation in fiber reinforcement materialreinforcement material

When stressed individual fibres When stressed individual fibres may break at a flaw, but the may break at a flaw, but the overall strength of the material is overall strength of the material is not prejudiced as the matrix bonds not prejudiced as the matrix bonds the remaining fibres together.the remaining fibres together.

Even quite short fibre whiskers or Even quite short fibre whiskers or particles can enhance the strength particles can enhance the strength of the matrix, particularly with of the matrix, particularly with respect to tensile and flexural respect to tensile and flexural stresses.stresses.

Matrix and reinforcement Matrix and reinforcement combinedcombined

When the resin systems are combined with When the resin systems are combined with reinforcing fibers such as glass, carbon and reinforcing fibers such as glass, carbon and Aramid (Kevlar), exceptional properties can be Aramid (Kevlar), exceptional properties can be obtained. obtained.

The resin matrix spreads the load applied to the The resin matrix spreads the load applied to the composite between each of the individual fibers composite between each of the individual fibers and also protects the fibers from damage caused and also protects the fibers from damage caused by abrasion and impact. by abrasion and impact.

High strengths and stiffness, ease of moulding High strengths and stiffness, ease of moulding complex shapes, high environmental resistance complex shapes, high environmental resistance all coupled with low densities, make the resultant all coupled with low densities, make the resultant composite superior to metals for many composite superior to metals for many applications. applications.

Properties of PMC’sProperties of PMC’s

Since PMC’s combine a Since PMC’s combine a resin system and resin system and reinforcing fibers, the reinforcing fibers, the properties of the properties of the resulting composite resulting composite material will combine material will combine some of the properties of some of the properties of the resin on its own with the resin on its own with those of the fibers on those of the fibers on their own.their own.

Metal matrix compositesMetal matrix composites

Increasingly found in the automotive industry, these Increasingly found in the automotive industry, these materials use a metal such as aluminium as the matrix, materials use a metal such as aluminium as the matrix,

and reinforce it with particles or fibers such as silicon and reinforce it with particles or fibers such as silicon carbide SiC. carbide SiC.

Particulate SiCParticulate SiCpp/Al and whisker SiC/Al and whisker SiCww/Al were extensively /Al were extensively characterized and evaluated during the 1980s. characterized and evaluated during the 1980s. MMC’s can also use continuous fibre reinforcement MMC’s can also use continuous fibre reinforcement (e.g. Graphite / Aluminium or Graphite / Magnesium)(e.g. Graphite / Aluminium or Graphite / Magnesium)Expensive and difficult to produce, MMC’s are mainly Expensive and difficult to produce, MMC’s are mainly used where their special benefits (e.g. weight saving) used where their special benefits (e.g. weight saving) outweigh cost considerations – such as on the space outweigh cost considerations – such as on the space shuttle.shuttle.

Metal matrix compositesMetal matrix composites Composites with aluminium and magnesium Composites with aluminium and magnesium

matrices have been investigated extensively, matrices have been investigated extensively, and recently steel matrix composites have and recently steel matrix composites have gathered increased interest. gathered increased interest.

In these composites, stainless steels, tool In these composites, stainless steels, tool steels and precipitation hardened steels have steels and precipitation hardened steels have been used as the matrix material. been used as the matrix material.

The particulate reinforcements can be oxides The particulate reinforcements can be oxides (Al(Al22OO33, Y, Y22OO33), carbides (TiC, Cr), carbides (TiC, Cr33CC22, VC, NbC), , VC, NbC), nitrides (TiN, Sinitrides (TiN, Si33NN44), and borides (TiB), and borides (TiB22, CrB, CrB22). ).

Ceramic matrix compositesCeramic matrix compositesCeramics have a high compressive Ceramics have a high compressive strength but low tensile strength. strength but low tensile strength. Combining with a high tensile Combining with a high tensile reinforcement gives very strong hard reinforcement gives very strong hard materials.materials.

Used in high temperature environments, Used in high temperature environments, such as jet engines, CMC’s use a ceramic such as jet engines, CMC’s use a ceramic as the matrix and reinforce it with short as the matrix and reinforce it with short fibres, or whiskers such as those made fibres, or whiskers such as those made from silicon carbide and boron nitride.from silicon carbide and boron nitride.

Super hard coatingsSuper hard coatings

DiamondDiamond B-C-N (Boron – Carbon – Nitrogen) coatingsB-C-N (Boron – Carbon – Nitrogen) coatings Ti – B – N Ti – B – N and and Ti – B – C – NTi – B – C – N Biocompatible super hard coatings for Biocompatible super hard coatings for

medical devicesmedical devices

About coatings:About coatings:

Nanostructured materialsNanostructured materials

Fullerenes: Fullerenes: Molecular structures of carbonMolecular structures of carbon

‘‘Fullerenes’ is a generic term for the third carbon Fullerenes’ is a generic term for the third carbon molecule that follows graphite and diamond. molecule that follows graphite and diamond.

Fullerenes are composed of a network structure, Fullerenes are composed of a network structure, either in a spherical or a tubular form, where 60 either in a spherical or a tubular form, where 60 or more carbon atoms are strongly bonded or more carbon atoms are strongly bonded together. together.

The atoms that make up Fullerenes are the same The atoms that make up Fullerenes are the same carbon atoms as those in graphite. carbon atoms as those in graphite.

C60 is one of the representative examples, and is C60 is one of the representative examples, and is a spherical aggregate of 60 carbon atoms, with a a spherical aggregate of 60 carbon atoms, with a diameter of approximately 0.7 nanometers diameter of approximately 0.7 nanometers (one nanometer equals 1/1,000,000,000 meter). (one nanometer equals 1/1,000,000,000 meter).

Fullerene structuresFullerene structures

Applications of fullerenesApplications of fullerenes

Electrochemical properties – use in Electrochemical properties – use in batteries and fuel cellsbatteries and fuel cells

Gas Storage properties – storage of Gas Storage properties – storage of hydrogenhydrogen

Mechanical properties – lubricants and Mechanical properties – lubricants and super hard materialssuper hard materials

Electrical properties – superconductorsElectrical properties – superconductors Optical properties Optical properties

Carbon nanotubesCarbon nanotubes

Carbon nanotubes are fibers with a Carbon nanotubes are fibers with a tensile strength many times that of tensile strength many times that of steelsteel

They are being postulated as a They are being postulated as a solution to the construction of a ‘space solution to the construction of a ‘space elevator’ where a geostationary elevator’ where a geostationary satellite is tethered to the earth, and satellite is tethered to the earth, and elevators run up and down the cable elevators run up and down the cable raising materials into orbit.raising materials into orbit.

AerogelsAerogels Made of inexpensive silica, aerogels can be Made of inexpensive silica, aerogels can be

fabricated in slabs, pellets, or most any shape fabricated in slabs, pellets, or most any shape desirable and have a range of potential uses. By desirable and have a range of potential uses. By mass or by volume, silica aerogels are the best solid mass or by volume, silica aerogels are the best solid insulator ever discovered. Aerogels transmit heat insulator ever discovered. Aerogels transmit heat only one hundredth as well as normal density glass. only one hundredth as well as normal density glass. Sandwiched between two layers of glass, transparent Sandwiched between two layers of glass, transparent compositions of aerogels make possible double-pane compositions of aerogels make possible double-pane windows with high thermal resistance. Aerogels windows with high thermal resistance. Aerogels alone, however, could not be used as windows alone, however, could not be used as windows because the foam-like material easily crumbles into because the foam-like material easily crumbles into powder. Even if they were not pulverized by the powder. Even if they were not pulverized by the impact of a bird, after the first rain they would turn impact of a bird, after the first rain they would turn to sludge and ooze down the side of the house. to sludge and ooze down the side of the house.

Aerogels as insulatorsAerogels as insulators Aerogels are a more efficient, lighter-weight, and Aerogels are a more efficient, lighter-weight, and

less bulky form of insulation than the polyurethane less bulky form of insulation than the polyurethane foam currently used to insulate refrigerators, foam currently used to insulate refrigerators, refrigerated vehicles, and containers. refrigerated vehicles, and containers.

They have another critical advantage over foam. They have another critical advantage over foam. Foams are blown into refrigerator walls by Foams are blown into refrigerator walls by chlorofluorocarbon (CFC) propellants, the chemical chlorofluorocarbon (CFC) propellants, the chemical that is the chief cause of the depletion of the that is the chief cause of the depletion of the earth's stratospheric ozone layer. According to the earth's stratospheric ozone layer. According to the Environmental Protection Agency, 4.5 to 5 percent Environmental Protection Agency, 4.5 to 5 percent of the ozone shield over the United States was of the ozone shield over the United States was depleted over the last decade. depleted over the last decade.

Facts about aerogelsFacts about aerogels They are 39 times more insulating than the best fibreglass They are 39 times more insulating than the best fibreglass

insulation. insulation. They are 100 times less dense than glass. They are 100 times less dense than glass. A wafer thin layer is sufficient to protect a hand from a A wafer thin layer is sufficient to protect a hand from a

blowtorch just inches away from it. blowtorch just inches away from it. A block the size of a person weighs less than a pound, looks A block the size of a person weighs less than a pound, looks

like it would blow away in a slight breeze, yet could support like it would blow away in a slight breeze, yet could support a small car. a small car.

They were used as insulation on the rover vehicle of the They were used as insulation on the rover vehicle of the Mars Pathfinder. Mars Pathfinder.

The Marshall Space Flight Center has already provided The Marshall Space Flight Center has already provided specifications for aerogels to over 50 companies and specifications for aerogels to over 50 companies and research institutes for products as diverse as diving suits, research institutes for products as diverse as diving suits, industrial insulation, medical containers and windows. industrial insulation, medical containers and windows.

The value of the worldwide market for low-cost aerogels is The value of the worldwide market for low-cost aerogels is projected to reach $10 billion by the year 2005.projected to reach $10 billion by the year 2005.

Applications of aerogelsApplications of aerogels

Solid insulationSolid insulation Silica aerogels are very light in weight Silica aerogels are very light in weight

and have an R-value up to R25 per inchand have an R-value up to R25 per inch Electrodes for batteriesElectrodes for batteries

Vanadium oxide aerogels have very Vanadium oxide aerogels have very promising properties for use in Lithium promising properties for use in Lithium cellscells

Today’s newsToday’s news

Organic-inorganic hybrids Organic-inorganic hybrids Under investigation by Prof J McKenzie at UCLA Under investigation by Prof J McKenzie at UCLA

Textile composites Textile composites Organic compositesOrganic composites Geopolymers – a better cement / concreteGeopolymers – a better cement / concrete Conjugated polymers Conjugated polymers

For semiconductors and light emitting devicesFor semiconductors and light emitting devices

ResourcesResources

www.azom.comwww.azom.com A to Z of materials A to Z of materials http://www.seas.ucla.edu/ms/http://www.seas.ucla.edu/ms/ http://http://

www.plasticsusa.com/polylist.htmlwww.plasticsusa.com/polylist.htmldatasheets for all common plasticsdatasheets for all common plastics

http://www.materials.ac.uk/http://www.materials.ac.uk/ http://bell-labs.com/org/http://bell-labs.com/org/

physicalsciences/physicalsciences/