Best physics ppt

1. Advanced Engineering materials

2. Types of Materials
Metals
• High density
• Medium to
high melting
point
• Medium to
high elastic
modulus
• Reactive
• Ductile
CeramicsCeramics
• Low densityLow density
• High meltingHigh melting
pointpoint
• Very highVery high
elasticelastic
modulusmodulus
• UnreactiveUnreactive
• BrittleBrittle
PolymersPolymers
• Very lowVery low
densitydensity
• Low meltingLow melting
pointpoint
• Low elasticLow elastic
modulusmodulus
• VeryVery
reactivereactive
• Ductile andDuctile and
brittle typesbrittle types
OrganicsOrganics
(wood, paper, textiles)(wood, paper, textiles)
• SustainableSustainable
• RecyclableRecyclable
• BiodegradableBiodegradable
• Easily workedEasily worked
• FlammableFlammable
• Share propertiesShare properties
of compositesof composites

3. Metals and Alloys
Metals are the most common of the elements.
Strong, with good conductivity for electricity and heat.
Mostly easily worked.
• Bronze for spearheads and axes
• Steel
• Aluminium, Magnesium
• Titanium: as strong as steel but 45% lighter
• Shape memory alloys

4. Polymers
Flexible Thermoplastic (PE, PU)
Rigid Thermoplastic (PVC, PS)
Rigid Thermosets (EP, PF)
Elastomers or rubbers

5. Ceramics
A ceramic is a
composite consisting
of hard granules
bound together by a
‘glue’ often like glass.
Examples:
Stone
Limestone (CaCO3)
Sandstone (SiO2)
Granite (alum inosilicates)
Cement and Concrete
Mixtures of lime (CaO),
silica (SiO2) and
alumina (Al2O3)
The CaO reacts with water
and carbon dioxide from the air
to form Ca2CO3(limestone)

6. Microstructure of ceramics
Engineering ceramic – Al2O3Pottery ceramic

7. Properties of ceramics
• Extremely hard and resistant to wear
• Very high melting point
• Resistant to chemical attack
• High compressive strength
• Low and variable tensile strength
• Low density ( as compared to steel)
• Ceramic components are not easy to make because of
their high mp and hard/brittle so can’t be machined.

8. Organic materials
• Have been used since the stone age eg wood or bone
handle for stone axe.
• Fibre for ropes
• Sinew for bow string
• Timber for houses and furniture
• Paper and cardboard for packaging
• Composites e.g. srbp for electrical components
• Glues and varnishes

9. Wood
• Has a grain structure with directionally oriented
fibers
• High compressive strength
• Good tensile strength along grain axis
• Weak across grain
• Prone to decay and infestation eg woodworm –
however look at timber used for staithes at Dunston

10. Composites
In its most basic form a
composite material is one
which is composed of at
least two elements working
together to produce
material properties that are
different to the properties
of those elements on their
own.
The properties of a
material depend on the
kind of stress it is exposed
to. For example concrete
has a good compressive
strength, but a low tensile
strength. This is overcome
by reinforcing with steel
rods - making a composite.

11. Types of stress
Tension Compression
Shear Flexion

12. Tensile strength and tensile modulus
Tensile strength Tensile modulus (stiffness)

13. Three main groups of
engineering composites
• Polymer matrix composites
• Metal matrix composites
• Ceramic matrix composites

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

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

16. Reinforcement
Materials such as glass, aramid (kevlar), carbon and boron have extremely
high tensile and compressive strength but in ‘solid form’ these properties
are not readily apparent. This is due to the fact that when stressed,
random surface flaws will cause each material to crack and fail well below
its theoretical breaking point. To overcome this problem, the material is
produced in fiber form, so that, although the same number of random
flaws will occur, they will be restricted to a small number of fibers with
the remainder exhibiting the material’s theoretical strength.

17. Crack propagation in bulk
reinforcement material

18. Crack propagation in fiber
reinforcement material
When stressed individual fibres may break
at a flaw, but the overall strength of the
material is not prejudiced as the matrix
bonds the remaining fibres together.
Even quite short fibre whiskers or
particles can enhance the strength of the
matrix, particularly with respect to tensile
and flexural stresses.

19. Matrix and reinforcement combined
• When the resin systems are combined with reinforcing fibers
such as glass, carbon and Aramid (Kevlar), exceptional
properties can be obtained.
• The resin matrix spreads the load applied to the composite
between each of the individual fibers and also protects the fibers
from damage caused by abrasion and impact.
• High strengths and stiffness, ease of moulding complex shapes,
high environmental resistance all coupled with low densities,
make the resultant composite superior to metals for many
applications.

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

21. Metal matrix composites
Increasingly found in the automotive industry, these
materials use a metal such as aluminium as the matrix,
and reinforce it with particles or fibers such as silicon carbide
SiC.
Particulate SiCp/Al and whisker SiCw/Al were extensively
characterized and evaluated during the 1980s.
MMC’s can also use continuous fibre reinforcement (e.g.
Graphite / Aluminium or Graphite / Magnesium)
Expensive and difficult to produce, MMC’s are mainly used
where their special benefits (e.g. weight saving) outweigh cost
considerations – such as on the space shuttle.

22. Metal matrix composites
• Composites with aluminium and magnesium
matrices have been investigated extensively, and
recently steel matrix composites have gathered
increased interest.
• In these composites, stainless steels, tool steels
and precipitation hardened steels have been used
as the matrix material.
• The particulate reinforcements can be oxides
(Al2O3, Y2O3), carbides (TiC, Cr3C2, VC, NbC),
nitrides (TiN, Si3N4), and borides (TiB2, CrB2).

23. Ceramic matrix composites
Ceramics have a high compressive strength but low tensile strength.
Combining with a high tensile reinforcement gives very strong hard
materials.
Used in high temperature environments, such as jet engines, CMC’s
use a ceramic as the matrix and reinforce it with short fibres, or
whiskers such as those made from silicon carbide and boron nitride.

24. Super hard coatings
• Diamond
• B-C-N (Boron – Carbon – Nitrogen) coatings
• Ti – B – N and Ti – B – C – N
• Biocompatible super hard coatings for medical devices
About coatings:About coatings:

25. Fullerenes:
Molecular structures of carbon
• ‘Fullerenes’ is a generic term for the third carbon molecule that
follows graphite and diamond.
• Fullerenes are composed of a network structure, either in a
spherical or a tubular form, where 60 or more carbon atoms are
strongly bonded together.
• The atoms that make up Fullerenes are the same carbon atoms as
those in graphite.
• C60 is one of the representative examples, and is a spherical
aggregate of 60 carbon atoms, with a diameter of approximately
0.7 nanometers
(one nanometer equals 1/1,000,000,000 meter).

26. Fullerene structures

27. Applications of fullerenes
• Electrochemical properties – use in batteries
and fuel cells
• Gas Storage properties – storage of hydrogen
• Mechanical properties – lubricants and super
hard materials
• Electrical properties – superconductors
• Optical properties

28. Carbon nanotubes
• Carbon nanotubes are fibers with a tensile strength
many times that of steel
• They are being postulated as a solution to the
construction of a ‘space elevator’ where a
geostationary satellite is tethered to the earth, and
elevators run up and down the cable raising materials
into orbit.

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

30. Aerogels as insulators
• Aerogels are a more efficient, lighter-weight, and less
bulky form of insulation than the polyurethane foam
currently used to insulate refrigerators, refrigerated
vehicles, and containers.
• They have another critical advantage over foam. Foams
are blown into refrigerator walls by chlorofluorocarbon
(CFC) propellants, the chemical that is the chief cause of
the depletion of the earth's stratospheric ozone layer.
According to the Environmental Protection Agency, 4.5 to
5 percent of the ozone shield over the United States was
depleted over the last decade.

31. Facts about aerogels
• They are 39 times more insulating than the best fibreglass insulation.
• They are 100 times less dense than glass.
• A wafer thin layer is sufficient to protect a hand from a blowtorch just
inches away from it.
• 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 a small car.
• They were used as insulation on the rover vehicle of the Mars Pathfinder.
• The Marshall Space Flight Center has already provided specifications for
aerogels to over 50 companies and research institutes for products as
diverse as diving suits, industrial insulation, medical containers and
windows.
• The value of the worldwide market for low-cost aerogels is projected to
reach $10 billion by the year 2005.

32. Applications of aerogels
• Solid insulation
• Silica aerogels are very light in weight and have an R-value
up to R25 per inch
• Electrodes for batteries
• Vanadium oxide aerogels have very promising properties
for use in Lithium cells