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					Composite Materials



                 By:
                 Engr. Rizwan Nasir
                 B.Sc. Chemical Engineering
                 13 October, 2009
Definition


• The word 'composites' has a modern ring. But
  using the high strength of fibres to stiffen and
  strengthen a cheap matrix material is probably
  older than the wheel. almost all natural
  materials which must bear load--wood, bone,
  muscle--are composites.
• The composite industry, however, is new. It
  has grown rapidly in the past 30 years with the
  development of fibrous composites..."
Composite materials – Introduction


• Definition: a material composed of 2 or more
  constituents
  – Reinforcement phase (e.g., Fibers)
  – Binder phase (e.g., compliant matrix)

• Advantages
  –   High strength and stiffness (rigidity)
  –   Low weight ratio
  –   Material can be designed in addition to the structure
  –   Can manufacture structures and eliminate joints
Natural composites




•   Fish fins
•   Muscles
•   Bird wings
•   Wood
•   Composite materials are like
    sandwiches. A good sandwich
    contains a variety of ingredients to
    yield a taste that no single ingredient
    could provide by itself.
•   Similarly, composite materials are
    those which are formed from two or
    more materials producing properties or
    characteristics that could not be
    obtained from any one material.
•   Composites consist of one or more
    discontinuous phases fixed in a
    continuous phase. The discontinuous
    phase is usually harder and stronger
    than the continuous phase and is
    called the reinforcement or reinforcing
    material, whereas the continuous
    phase is termed the matrix.
Applications


   – Aerospace industry
   – Sporting goods
   – Automotive
   – Construction
Types of Composites

 Matrix              Metal                          Ceramic                       Polymer
 phase/Reinforceme
 nt Phase
                     Powder metallurgy              Cermets (ceramic-             Brake pads
 Metal
                     parts – combining              metal composite)
                     immiscible metals

 Ceramic             Cermets, TiC, TiCN             SiC reinforced                Fiberglass
                     Cemented carbides –            Al2O3
                     used in tools
                                                    Tool materials
                     Fiber-reinforced metals


 Polymer                                                                          Kevlar fibers in an
                                                                                  epoxy matrix

 Elemental           Fiber reinforced                                             Rubber with carbon
                     metals                                                       (tires)
 (Carbon,            Auto parts                                                   Boron, Carbon
 Boron, etc.)        aerospace                                                    reinforced plastics


                          MMC’s                          CMC’s                      PMC’s
                          Metal Matrix Composites        Ceramic Matrix Comp’s.     Polymer Matrix Comp’s
Fibers - Glass

 • Most widely used fiber
 • Uses: piping, tanks, boats, sporting goods
 • Advantages
    – low cost
    – Corrosion resistance
    – Low cost relative to other composites:
 • Disadvantages
    – Relatively low strength
    – High elongation
    – Moderate strength and weight
 • Types:
    – E-Glass - electrical, cheaper
    – S-Glass - high strength
Fibers - Aramid (Kevlar, Twaron)


 • Uses:
   – High performance replacement for glass fiber
 • Examples
   – shield, protective clothing, industrial, sporting
     goods
 • Advantages:
      • Higher strength and lighter than glass
      • More ductile than carbon
Fibers - Carbon


 • 2nd most widely used fiber
 • Examples
   – aerospace, sporting goods
 • Advantages
   –   high stiffness and strength
   –   Low density
   –   Intermediate cost
   –   Properties:
        • Diameter: 5-8 microns, smaller than human hair
           – Fibers grouped into tows or yarns of 2-12k fibers
PAN (Polyacrylonitrile)


• Carbon fiber composite material are
  produced by PAN with the help of these
  processing stages:
   – Stabilization
   – Carbonization
   – Graphitization
Stabilization



 • In this process PAN fiber are stretched
   to align the fiber network with each
   network.
 • Then they are oxidize in air at
   temperature about 200 – 220oC while
   holding in tension.
Carbonization


• In this process the high strength carbon fiber is
  carbonized.
• The stabilized PAN fiber are heated until they
  become transformed into carbon fibers by the
  elimination of oxygen, nitrogen and hydrogen.
• The carbonization process is carried out at the
  temperature of 1000 – 1500oC
Graphitization


• It is used if we desired the product of
  high elasticity.
• This process is carried out at the
  temperature of 1800oC.
Aramids Fiber


• Aramid fiber is the name for aromatic poly
  amide fibers.
• Aramid fibers are available under the name of
  Kevlar.
• At the present time there are two commercial
  types are available.
   – Kevlar – 29
   – Kevlar – 49
Kvelar – 29


• It is the low density high strength aramid
  fiber such application as cables, ropes
  and missiles.
•
Kevlar – 49


 • It is a useful fibre as reinforcement plastic in
   composite material for aerospace, automobile,
   industrial application and also shipping
   industry .
 • Its density is higher than Kevlar – 29.
    – In general Kevlar aramid is used for high
      performance composite application where light
      weight, high strength, resistance to stress.
An education isn't how much you have
   committed to memory, or even how
    much you know. It's being able to
differentiate between what you do know
           and what you don't.

          Anatole France

				
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