Fibre Reinforced Plastics (FRP)

FIBRE REINFORCED PLASTICS (FRP)

Fibre reinforced plastics consist of fibres in a polymer resin matrix. Because of their room temperature properties, ease of fabrication and cost, they are used in large quantities. The commonly used fibres are

(a) Glass Fibre Reinforced Plastics (GFRP)

(b) Aramid Fibre Reinforced Plastics (AFRP)

(c) Carbon Fibre Reinforced Plastics (CFRP)

 (a) Glass Fibre Reinforced Plastics (GFRP)

Glass fibres are the most widely used and the least expensive of all the fibres.

The most generally used glass fibre is E-glass and common polymer matrix materials are polyesters and vinyl esters.

Polyesters are used for general structures. Epoxies are used in high strength applications. High purity silica fibres in polyamide resins are used for applications where the service temperature is as high as 300°C.

GFRP composites have very high specific strength. But they are not rigid and are limited to service temperatures below 200°C

The fiber diameters normally range from 3 to 20 μm. Glass is popular as a fiber reinforcement material for the following reasons.

1. It is easily drawn into high strength fibers from the molten state.

2. It is readily available and may be fabricated into a bas-aanly glass-reinforced plastic economically using a wide variety of composite-manufacturing techniques.

3. As a fiber, it is relatively strong, and when embedded in a plastic matrix, it produces a composite having a very good specific strength.

4. When coupled with various plastics, it possesses a chemical inertness that renders the composite useful in a variety of corrosive environments. 

Applications of FRP

Used in automotive and marine bodies, leaf springs, pipes, storage containers, sporting goods and industrial floorings.

(b) Aramid fibre reinforced plastics

Aramid fibres, are desirable where lightweight, high tensile strength and high impact strength are important. Moreover they provide resistance to creep and fatigue.

The major disadvantage of aramid fibre reinforced composites are their low compressive strengths, moisture absorption and difficulty in cutting or machining.

Kevlar 49 is the most common aramid fibre. The common matrix materials are the epoxies and polyesters.] 

Applications

Used in bullet proof vests, sporting goods, pressure vessels, missile cases, automotive brake and clutch linings gaskets.

(c) Carbon fibre reinforced plastics

Carbon fibre composites have much lower densities, higher strength and higher stiffness-to-weight ratio. This composite has low coefficient of thermal expansion and this gives better dimensional stability. The commonly used matrix materials are epoxy, polyester, polyether ether ketone (PEEK) and polyphenylene sulfide (PPS).

1. Carbon fibers have the highest specific modules and to a specific strength of all reinforcing fiber materials.

2. They retain their high e modulus and high strength at elevated temperatures; high temperature oxidation, however, may be a problem.

3. At room temperature carbon fibers are not affected by moisture nor a wide variety of solvents, acids and bases.

4. These fibers exhibit, a diversity of physical and mechanical characteristics allowing, composites incorporating these fibers to have specific engineered properties.

5. Fiber and composite manufacturing processes have been developed that are relatively inexpensive and cost effective.

Carbon fibers are not totally crystalline, but are composed of both graphitic and noncrystalline regions. The fiber diameters normally range between 4 and 10 mm, both continuous and chopped forms are available.

Applications

Used in sports and recreational equipment, filament wound rocket motor cases, pressure vessels, commercial and military aircraft, helicopter structures and satellites.