FIBREGLASS REINFORCED PLASTIC  (FRP)

Composite:  A combination of one or more materials differing in form or composition on a macro scale. The constituents retain their identities; i.e. they do not dissolve or merge completely into one another, although they act in concert.  Normally, the components can be physically identified and exhibit an interface between one another.

A fibre glass reinforced plastic (FRP) composite is a material system consisting of glass fibre reinforcement, plastic resin and additives, combined and processed to meet specific functional performance and manufacturing criteria for the finished product or part. By selecting the right combination of resin and glass fibres, the designer can create a product or part that meets the most demanding of product specifications.

Composite systems, glass fibre-resin, have become industrially important in all areas where a high strength-to-weight ratio is required and in applications where complex shapes of limited number are called for. The present world annual output of glass fibre reinforced plastics is approximately 750,000 tons, the main applications being in the fields of land transportation, boats, building construction, aircraft and missiles.

 

FIBREGLASS REINFORCEMENTS

The most commonly used glass fibre reinforcements are:-

o       Chopped Strand Mat

o       Roving

o       Woven Roving

o       Chopped  Strands

o       Yarn

Fibreglass reinforcement and yarn products are manufactured from `E` glass in fibre form. `E` (Electrical) glass, the most commonly used composition for glass fibre reinforcements, combines the advantages of high heat resistance, low moisture absorbency and superior electrical properties. The result is a unique combination of physical properties.

HIGH TENSILE STRENGTH

On weight for weight basis, fibre glass reinforcements are twice as strong as steel wire.

DIMENSIONAL STABILITY

No more than nominal 3% elongation under maximum stress.

HIGH HEAT RESISTANCE

Retains 50% of tensile strength at 650 F (340 C)

CHEMICAL RESISTANCE

High resistant to attack by most chemical

LOW MOISTURE ABSORPTION

Moisture cannot penetrate the surface of glass filaments

 

3. RESIN

The primary functions of the resin are to transfer stress between the reinforcing fibers, act as a glue to hold the fibers together, and protect the fibers from mechanical and environmental damage. Thermoset Resin is formed by cross linking polymer chains.  A thermoset cannot be melted and recycled because the polymer chains form a three dimensional network. Polyester Resins Considered the "workhorse" of the composites industry, these resins offer a balance of properties (including mechanical, chemical and electrical) dimensional stability, cost and ease of handling or processing. Polyesters are versatile because of their ability to be modified or tailored. Ortho-and Iso-Polysters are two types of polyester resins formulated to enhance corrosion resistance.

The most common resins used in the production of FRP are polyesters, vinyl esters, epoxy and phenolics.

 

4. MOULDING TECHNIQUES

Hand lay-up:  A process where each layer of the laminate is individually fabricated one at a time on a contact mold. Allows precise control of the glass content and ensures that the glass is thoroughly wetted out with resin. This fabrication method is the most labor intensive.

Spray-up:  Similar to hand lay-up but glass and resin is sprayed on to the mold. Less labor intensive than hand lay-up but poor control of laminate thickness and quality due to air bubbles.

Resin Transfer Molding:  Process where a closed mold is filled with glass and then injected with resin under pressure. The system is allowed to cure and then the mold is opened to remove the part.

Pultrusion:  Pultrusion is a continuous process for manufacturing composites that have a cross-sectional shape. The process consists of pulling a fiber - reinforcing material through a resin impregnation bath and through a shaping die. The dimensions and shape of the die will define the finished part being fabricated.

 

ADVANTAGES OF FRP

High Strength:

FRP composites have excellent strength to weight properties. By weight, FRP composites surpass the tensile strength of iron, carbon and stainless steels.

Light Weight:

FRP composites offer more strength by weight than most non-reinforced plastics and many metals. Light weight and strength are the primary reasons for the automobile industry using fibre glass reinforced plastic body parts.

Dimensional Stability:

FRP can maintain the critical tolerances required of the most demanding structural applications. From the hulls of commercial fishing boats to the structural frames and components of business equipment, FRP meets the most stringent material stiffness, dimensional tolerance, weight and cost criteria.

Corrosion Resistant

FRP does not rust or corrode and it is resistant to attack from most chemicals. These qualities alone make fibreglass composites an invaluable material for many segments of industry.

Lower Tooling Cost

FRP parts can be made efficiently with a variety of manufacturing process. The total tooling cost for reinforced composite parts is normally substantial lower than the multiple forming tools required to produce the same finished product in metal.

Design Flexibility

Perhaps no other material offers more in the way of design flexibility than FRP. It can be used for a verity of applications. From parts for engine to TV antennas, from seating to chemical pipelines, from skis to automobiles and truck bodies. The opportunity for successful, cost effective application of fibreglass reinforced plastic composites makes this system an integral part of product design.

Excellent Electrical Resistance

FRP is a very low conductor of electricity. As such it has a high dielectric strength for applications in electrical and electronic industries. Step ladders are also being made of FRP not only for its light weight and raggedness but also for its electrical resistance properties.

Moulded in Colour and surface finishes

Colour can be added to FRP as a part of the mix, often eliminating the need for a separate painting process. In addition Class ‘A’ surface finishes can be moulded in reducing finishing time while enhancing the beauty of the finished product.

 

APPLICATIONS

Building Industry

Construction offers many possibilities to the beneficial use of FRP. Panels, false ceilings, building facades, fancy awnings and porches, aesthetically pleasing bus stand are some of the many imaginative applications. More standard applications are weather-proof chairs and benches in stadia, and passenger gathering stations viz. Airport , Railway and Bus stations or public parks, water tanks, bath tubs, sinks etc.

FRP panels sandwiching insulation media such as urethane foams have been used to construct complete cold storage and they provide more energy-efficient systems.

Pultruded sections in FRP provide angles, beams, channels, pipes for light weight, maintenance-free structures and window frames, with glass fibre reinforced Nylon providing weather-proof hinges.

Highly translucent corrugated sheets replace glass in green-house applications and asbestos sheets in factory sheds providing natural light and savings in electric power.

Chemical industry:

The chemical industry covers a spectrum including organic chemicals, paper, breweries, food beverage industry, inorganic chemicals, fertilizers, fibres and filament plants etc. Common products in these plants are storage tanks, pipes, ductings, fume hoods, scrubbers and casings.

Transportation and Marine:

By virtue or strength, lightness, ease of repair properties, FRP finds ready acceptance in transport industry. Road and rail tankers in FRP for corrosive liquids reduce carriage weight: truck drivers cabins, automobile bodies and body parts influence direct savings in fuel and maintenance.

FRP provides another advantage for Boats such as trawlers, yachts, row boats, patrol boats, coast guard cutters, buoys etc. By virtue of its lightness.

Electrical & Appliance industries:

Voltage stabiliser cases, fan cowls, switchgear body, junction boxes, street light canopies, business machine covers, typewriter casings, cassette recorder casings are common applications. Copper Clad laminates for printed circuit boards are made from glass-fabric epoxy prepregs. Pultrusion process yields high strength and electrically resistant switching arms, slot wedges and cross-arms for 11 KV transmission lines.

Protective Industry:

The superior strength against light weight property is seized by the protective helmets market for two wheeler drivers, construction workers and the Police Force.

This is not the end of applications. There can be many depending upon the need and suitability.