Composites are combinations of two materials, containing 'reinforcing phase' and 'matrix phase'. The reinforcing material and the matrix can be metal, ceramic, or polymer. The first phase made of materials which are strong with low densities while the matrix phase i
s usually a ductile or tough material. Concrete is an example for a composite, which is formed by mixing sand and rocks in a paste of cement. Concrete shows best compressive nature but less tensile strength unless supported with steel. Concrete is used in infrastructure and construction bodies like, bridges, roads etc. Polymer composites are made up of at least two distinct materials. For example, a plastic composite consists of a combination of polymer resin matrix and fibrous material. The combination of materials having different properties yields a unique classs of materials which provide a user with the tailerability, which can be used to fulfill specific requirements. Polymer composites are known for higher strength per unit weight, so it can be translated directly into light weight materials (weight savings). Reduction in weight results in more efficient structures, which also reduces the energy cost and hence the material cost. Polymer composites offer many advantages such as resistance to fatigue and corrosion, low cost of fabrication etc.
s usually a ductile or tough material. Concrete is an example for a composite, which is formed by mixing sand and rocks in a paste of cement. Concrete shows best compressive nature but less tensile strength unless supported with steel. Concrete is used in infrastructure and construction bodies like, bridges, roads etc. Polymer composites are made up of at least two distinct materials. For example, a plastic composite consists of a combination of polymer resin matrix and fibrous material. The combination of materials having different properties yields a unique classs of materials which provide a user with the tailerability, which can be used to fulfill specific requirements. Polymer composites are known for higher strength per unit weight, so it can be translated directly into light weight materials (weight savings). Reduction in weight results in more efficient structures, which also reduces the energy cost and hence the material cost. Polymer composites offer many advantages such as resistance to fatigue and corrosion, low cost of fabrication etc. 
Polymer composites are synthesized by mixing fiber materials with polymer resin matrix and curing the same under high pressure and heat. The resin matrix used in polymer composites are polyesters, epoxy resins, phenol-formaldehyde resin, silicone resins, vinyl derivatives and polyamides. Resistance to high temperature is induced by using phenolic resins.The fibre is embedded in the matrix in order to result the stronger matrix. Fibre reinforced composites are stronger and light. They are four to five times stronger than steel. Use of this composites makes the automobiles lighter, and hence increases the fuel effieciency. 
Today polymer composites are very much required which can stand up to the torture in various applications and they are more preferred to many metals and materails for having following advantages.
- Polymer composites are very light in weight.
- They have high strength to weight ratio.
- Composite polymers are very strong and are more durable than ordinary conventional metals like steel and aluminium.
- Polymer composites are most convenienty used for aerospace applications due to its inherent properties.
- They are known for very good corrosion resistance and temperature resistance and also cutting resistance.
