Slide Contains the types of Composites and a brief explanation of MMC.

1. Metal Matrix Composites
By P.Pon Rajesh Kumar
M.E Engineering Design
College Of Engineering,Guindy

2. A materials system composed of two or more
physically distinct phases whose combination
produces aggregate properties that are
different from those of its constituents
Examples:
◦ Cemented carbides (WC with Co binder)
◦ Plastic molding compounds containing fillers
◦ Rubber mixed with carbon black
◦ Wood (a natural composite as distinguished from a
synthesized composite)

3. Composites can be very strong and stiff, yet very
light in weight, so ratios of strength-to-weight
and stiffness-to-weight are several times greater
than steel or aluminum
Fatigue properties are generally better than for
common engineering metalscommon engineering metals
Toughness is often greater too
Composites can be designed that do not corrode
like steel
Possible to achieve combinations of properties
not attainable with metals, ceramics, or polymers
alone

4. Disadvantages
Many of the polymer-based composites are
subject to attack by chemicals or solvents,
just as the polymers themselves are
susceptible to attack
Composite materials are generally expensiveComposite materials are generally expensive
Manufacturing methods for shaping
composite materials are often slow and costly

6. Primary Phase, Matrix
Secondary Phase,
Reinforcement

8. Protect phases from environment
Transfer Stresses to phases
Holds the imbedded phase in place,
usually enclosing and often concealing it
When a load is applied, the matrix sharesWhen a load is applied, the matrix shares
the load with the secondary phase, in
some cases deforming so that the stress is
essentially born by the reinforcing agent

17. Metal matrix composites (MMCs) possess
significantly improved properties including
high specific strength; specific modulus,
damping capacity and good wear resistance
compared to unreinforced alloys.
A metal matrix composite (MMC) is compositeA metal matrix composite (MMC) is composite
material with at least two constituent parts,
one being a metal.
The other material may be a different metal
or another material, such as a ceramic or
organic compound.

18. When at least three materials are present, it is
called a hybrid composite.
MMCs are made by dispersing a reinforcing
material into a metal matrix. The
reinforcement surface can be coated toreinforcement surface can be coated to
prevent a chemical reaction with the matrix.

19. The matrix is the monolithic material into which
the reinforcement is embedded, and is
completely continuous.
This means that there is a path through theThis means that there is a path through the
matrix to any point in the material, unlike two
materials sandwiched together.
The matrix is usually a lighter metal such as
aluminum, magnesium, or titanium, and provides
a compliant support for the reinforcement.

20. The reinforcement material is embedded into
the matrix.
It is used to change physical properties such
as wear resistance, friction coefficient, oras wear resistance, friction coefficient, or
thermal conductivity.
The reinforcement can be either continuous,
or discontinuous.

21. Aluminum matrix
Continuous fibers: boron, silicon carbide, alumina,
graphite
Discontinuous fibers: alumina, alumina-silica
Whiskers: silicon carbide
Particulates: silicon carbide, boron carbide
Magnesium matrix
Continuous fibers: graphite, alumina
Whiskers: silicon carbide
Particulates: titanium carbide
Copper matrix

22. Higher temperature capability
Fire resistance
Higher transverse stiffness and strength
No moisture absorptionNo moisture absorption
Higher electrical and thermal conductivities
Better radiation resistance
Fabric ability of whisker and particulate-reinforced MMCs
with conventional metalworking equipment.

23. Higher cost of some material systems .
Relatively immature technology .
Complex fabrication methods for fiber-
reinforced systems (except for casting).