introduction to composite material

Lec. No.(1)
Definition of Composite Materials
A composite material can be defined as a combination of two or more materials that results in better properties than those of the individual components used alone. In contrast to metallic alloys, each material retains its separate chemical, physical, and mechanical properties. The two constituents are a reinforcement and a matrix. The main advantages of composite materials are their high strength and stiffness, combined with low density, when compared with bulk materials, allowing for a weight reduction in the finished part. The reinforcing phase provides the strength and stiffness. In most cases, the reinforcement is harder, stronger, and stiffer than the matrix.

What are the various types of Matrices
in composites materials?
Matrices

Polymer matrix Metal matrix Ceramic matrix
Composite(PMC) composite(MMC) composite(CMC)

1)(Thermoset 1) Alloys 1) Glass (Epoxy, Polyester)
2) (Steels, Aluminiums)
2) Thermoplastics
2)(Semi conductors,
Cermets)
3) Cements
What are the types of reinforcement in composites materials?

1)Particulate
2)Flake
3)Fiber
4)Nano materials


Characteristics of Composite Materials
1) High specific strength and modulus, as well as high fatigue strength
2) Anisotropic
3) Designable or tailorable materials for both microstructure and
properties
4) Production of both material and structure or component in a single
operation - manufacturing flexible, net-shape, complex geometry
5) Corrosion resistance and durable
6) Other unique functional properties - damping, low CTE (coefficient of
thermal expansion.


Disadvantages of Composites
??High cost of fabrication of composites
??Mechanical characterization of a composite structure is
more complex than a metal structure
??Repair of composites is not a simple process compared to
that for metals
??Composites do not have a high combination of strength and
fracture toughness compared to metals
?? Composites do not necessarily give higher performance in
all the properties used for material selection: strength,
toughness, formability, joinability, corrosion resistance,

Applications
Applications include aerospace, transportation, construction, marine goods, sporting goods, and more recently infrastructure, with construction and transportation being the largest. In general, high-performance but more costly continuous-carbon-fiber composites are used .

1)GLASS FIBERS

GLASS FIBERS are among the most versatile industrial materials known today. They are readily produced from raw materials, which are available in virtually unlimited supply . They exhibit useful bulk properties such as hardness, transparency, resistance to chemical attack, stability, and inertness, as well as desirable fiber properties such as strength, flexibility, and stiffness . Glass fibers are used in the manufacture of structural composites, printed circuit boards and a wide range of special-purpose products . to achieve the high-performance characteristics of the resultant composite, two facets can be considered :-
First, the fibers should not be greatly degraded during processing either by handling or by chemical reaction, and second, the resultant fiber–matrix interface must have the characteristics necessary to prevent excess fiber–matrix bonding.
As should be clear from the discussion above, high-performance ceramics
must have superior structural and/or mechanical characteristics because they find application in some very demanding environments, e.g. rocket nozzles, heat exchangers, automobile engines and cutting tools. Yet another important factor is the cost of ceramics. The great challenge is to produce consistent and reliable ceramic components having superior properties but without excessive cost, i.e. they should be competitive on a cost/performance basis with the materials they seek to replace it.