(Metal Matrix Composites (MMCs

Properties of Composite Materials
-In selecting a composite material, an optimum combination of properties is usually sought, rather than one particular property
- Example: fuselage and wings of an aircraft must be lightweight and be strong, stiff, and tough
(Several fiber reinforced polymers possess this combination of properties)
Example: natural rubber alone is relatively weak-
(Adding significant amounts of carbon black to NR increases its strength dramatically).
Propertiesare Determined by Three Factors:
-The materials used as component phases in the composite.
-The geometric shapes of the constituents and resulting structure of the composite system.
The manner in which the phases interact with one another. -

Metal Matrix Composites (MMCs)
Metal matrix composites (MMCs), as the name implies, have a metal matrix.Examples of matrices in such composites include aluminum, magnesium, titanium, copper, and a dispersed ceramic or metallic phase. Ceramic reinforcement may be SiC, WC, Al2O3, SN, B4C, BN etc. whereas metallic reinforcement may be W, Cu etc.
Metals are mainly reinforced to increase or decrease their properties to suit the needs of design. For example, Comparing with monolithic metals, metal matrix composites have higher specific strength,higher specific stiffness,better fatigue resistance; better elevated temperature properties (higher strength, lower creep rate), lower coefficients of thermal expansion, and better wear resistance.
MMCs are usually utilized for Space Shuttle,commercial airliners, electronic substrates, bicycles, automobiles, golf clubs and a variety ofother applications.

The Most Important MMC Systems
- Aluminum matrix
Continous fiber: boron,silicon carbide, alumina, graphite.-
Discontinous fiber: alumina, alumina-silica.-
Whiskers: silicon carbide-
-Particulates: silicon carbide, boron carbide, titanium carbide.
Magnesium matrix.-
Copper matrix.-
Example: Al-SiC (silicon carbide)-
Metal matrix: Al, Ti, Mg, Fe, Cu, Ni-
Example: Al-Al2O3 (aluminum oxide)-