By: Engr. Rizwan Nasir B.Sc. Chemical Engineering 13 October, 2009 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 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 MMC’s CMC’s PMC’s Elemental (Carbon, Boron, etc.) Matrix phase/Reinforcement Phase Metal Ceramic Polymer Powder metallurgy parts – combining immiscible metals Cermets (ceramic-metal composite) Brake pads Cermets, TiC, TiCN Cemented carbides – used in tools Fiber-reinforced metals SiC reinforced Al2O3 Tool materials Fiberglass   Kevlar fibers in an epoxy matrix Elemental (Carbon, Boron, etc.) Fiber reinforced metals Auto parts aerospace Rubber with carbon (tires) Boron, Carbon 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 Advantages 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.

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