GLASS FIBRE REINFORCED PLASTIC AND ITS ARCHITECTURAL APPLICATIONS

This paper deals with glass fibre reinforced plastic, its composition, property, advantages, manufacturing technology and its application in civil engineering. It includes the architectural application of glass fibre reinforced plastic and its application techniques.

Keywords: Glass Fibre Reinforced Plastic (GFRP), Architecture, Applications, Properties.

1.0 INTRODUCTION

Over the last 30 years composite materials, plastic and ceramics have been dominating emerging materials. The volume and number of application of composite materials have grown steadily penetrating and conquering new market relentlessly.

Traditional construction materials like steel and concrete have exhibited signs of deterioration over the years in their long term performance due to the inherent nature of materials or weak resistance offered by these materials to adverse environmental condition. Retrofitting and rejuvenation of such structures require use of skilled labor, heavy equipment and excessive energy and is time consuming resulting in the rapid increase in the overall cost. These factors motivated researches to bring out the use of composite material to retrofit and strengthen structures.

A composite material is a three dimensional combination of at least two chemically and mechanically distinct material with a discrete interface separating them. Polymer composites are multi phase materials produced by combining polymer resins such as polyester, vinyl ester and epoxy with fillers and reinforcing fibres to produce a bulk material with properties better than those of the individual base material and offer the advantage of flexible design.

Under Graduate Student, Department of Civil Engineering, N.S.S College of Engineering, Palakkad-08, Kerala.

2. 0 GLASS FIBRE REINFORCED PLASTIC (GFRP)

The polymer composites have a variety of products of which glass fibre reinforced plastic (GFRP) is one of them. The varieties of products are mainly due to various types of fibres and their arrangements in the products.

Glass fibre reinforced plastic generally consists of three basic elements.

• Glass fibre
• Matrix
• Fibre matrix

2.1. Glass fibre

Glass fibre is used as a reinforcement to include the mechanical properties of cured resins and provide a usable product. Different types of glass fibres available are A glass, C glass, D glass, E glass, E-CR glass. E glass is generally used in glass fibre reinforced plastic.

2.2. Matrix

Matrix is used as a binder to bind the fibres together and transfer the stress to the individual fibre. It protects the fibres against abrasion, high impact and exposure to adverse environmental conditions. Generally unsaturated polyester resin and epoxy resin are used for GFRP.

2.3. Fibre matrix

Fibre matrix interface is a bond between fibre and matrix to resist stress due to uneven thermal expansion of fibres and matrices, shrinkage of resin during curing and to provide load transfer from matrix to reinforcement. Various additives are used to improve mechanical properties, protection and appearance.

GFRP is a thermosetting plastic. When GFRP is heated to a certain temperature a chemical reaction takes place that cause the molecules to bond together or cross-link. After polymerization it cannot return to its original form.

GFRP is mixed with fillers and reinforcement agents to get optimum property of a moulding compound. Fillers are often used to provide a bulk to the material, reduce the cost, and lower the bulk density or to produce aesthetic features. Fibres are used to reinforce and improve mechanical properties such as stiffness, strength etc. GFRP is the hardest and stiffest of all plastic and very little effected by change in temperature FRP have been prominent than other types of composites because most materials are stronger and stiffer in the fibrous form than any other form.

3.0 PROPERTIES OF GLASS FIBRE REINFORCED PLASTIC

3.1 Properties of glass fibre

A variety of different chemical compositions are commercially available. Common glass fibres are silica based (50%-60% SiO₂) and contain other oxides of calcium, boron, sodium, aluminium and iron. E glass is commonly used as the fibre. ‘E’ stands for electrical because E glass is good insulator besides having good strength and a reasonable young’s modulus.90% of glass fibres produced is E type. Its density is quite low and the strength to weight ratio with moderate young’s modulus of elasticity.

Tensile strength MPa	Young’s modulus GPa	Coefficient of Thermal expansion 10-6/ ˚K	Density g/cm3
1750	70	4.7	2.55

3.2 Properties of Matrix

The commonly used polymer matrices are polyester and epoxy resins polyester shrinks about 4% to 8% on curing and a good adhesion with glass fibres. But epoxy resins are co0stlier than polyester.

Density g/cm3	Tensile strength MPa	Flexural modulus MPa	Coefficient of Thermal expansion 10-6/ ˚K	Continuous service temperature ˚C
1.38	35-85	3000	8-11	25-85

The salient features of glass fibre reinforced plastic is its competitive installed cost, high strength, light weight, translucency, good resistance to weathering and fire the versatility of fabrication methods make it an ideal material in building construction.

4.0 ADVANTAGES OF GLASS FIBRE REINFORCED PLASTIC COMPARING OTHER CONSTRUCTION MATERIALS

· Weather resistance

· Chemical resistance

· High strength to weight ratio

· Design flexibility

· Light weight

· Part consolidation

· Colourability

· Zero maintenance

· Ease to repair

· Durability

· Light transmission

· Shock absorption in seismic resistant structure

Property	GRP	Aluminium	Steel
Corrosion resistance	Excellent resistance to Broad range of chemicals	Can cause galvanic corrosion	Subject to oxidation and corrosion requires painting
Weight	30%less than aluminium 50% less than steel	Requires lifting equipment	Requires lifting equipment
Electrical resistance	Non conductor	Conducts electricity	Conducts electricity
Thermal property	Non conductor	Conducts heat	Conducts heat
Finish and colour	Various pigments added to the resin as per requirement	Silver colour	Grey/black Need to be painted

5.0 GFRP AND FIRE

Two third portion of GFRP is polyester resin, which is a hydrocarbon and therefore combustible. In an actual fire the behaviour of GRP compares very well with other roofing materials even with some of those, which are non-combustible. Glass and asbestos-cement splinter crack in heat and send particle flying. Acrylics send down flaming droplets GRP burns away producing only smoke and leaving a black mat of the incombustible glass fibre itself. This mat prevents the spread of radiant heat into other parts of the roof structure. In particular with roof cladding it is some time advantageous for the roof to burn away over the source of a fire thus venting it, than to remain as a heat and smoke barrier forcing the fire to spread along the under side of the roof.

By the addition of inert fillers and certain chemicals, the spread of flame can be reduced and can make the product difficult to burn, but cannot make it incombustible. Fire protection can be given by coating GRP with infumescent paint and can be used for internal surface.

6.0 MANUFACTURING TECHNOLOGY OF GFRP

6.1. Hand lay up technology

It is a simple technique .An open mould is used to prepare a mat of glass roving. Epoxy resin is prepares by the stirrer. A small layer is applied on releasing film, on which the mould is kept. Epoxy resin is applied followed by a releasing film. Roller eliminates air bubbles. Complex shapes of bigger/smaller size can be produced.

Hand lay up technique need skilled labour. The quality of the product depends upon the operator skill.

6.2. Filament winding

The glass rovings are drawn through a resin bath to impregnate them with resin. The impregnate rovings are then wound under tension round the rotating mandrel; the mandrel is generally wrapped with a release film prior to wrapping with glass and resin. The winding angle depends on the strength and requirements. Some times mandrel may incorporate some means of heating systems. This method is suitable for manufacture of pipes, tubes, cylinders, sphere etc.

6.3. Resin transfer moulding

It is also known as resin injection, this technique produce better quality smooth moulding surfaced but it is more expensive.

6.4. Pultrusion

It is a suitable technique for both polyester and epoxy resin systems as well as for reinforced sections with glass, carbon, and synthetic fibres. This method is useful for sections of varying thickness and shapes.

6.5. 3-D weaving

The advantages 3-D weaving to obtain 3-D fabric is widely known but is costlier. Although 3-D weaving is still in its infancy, it has the potential to replace expensive titanium fittings, hinges, engine bladders etc.

6.6. Forming stamping, injection moulding, rolling

These manufacturing methods have great potential for high volume production, especially when combined with the use of thermo plastics. Application is limited to small to medium size parts. Sport goods and industrial products will benefits from this group of technologies.

7.0 APPLICATION OF GRP IN CIVIL ENGINEERING FIELD

7.1. Prefabricated housing

Prefabricated structures can be made by assembling modular panels at site. It is used suitably for security cabins, telephone booths, security watchtowers etc. the concept of low-density material between layers of GRP laminates is employed in the fabrication panels. It provides sound insulation thermal insulation dust proof environment etc.

7.2. Water storage tanks

The conventional (concrete/GI/MS) tanks are now replacing GRP tanks. The GRP tanks can be made in any shapes (rectangular, cylindrical etc). The main advantage of GRP is its lightweight and low maintenance cost.

7.3. Structural profiles

I beams, channels, equal and un equal angles, rectangular/circular rods, rectangular hallow sections etc, that are being made using steel and all the common profiles that are made by using steel and aluminium for structural purpose, can be made using GRP. The corresponding section being much lighter, have significantly better properties in flexure and tension i.e. the load bearing capacity of GRP section is much higher than a steel or aluminium structure. GRP structures can be bolted riveted and tapped like other structural sections.

Material	Specific gravity	Tensile strength Kg/mm2	Flexural strength Kg/mm2
GRP	1.5-1.8	40-60	40-80
Steel	7.8	34-50	34-50
Aluminium	2.7	9-17	14

7.4. Other applications in civil engineering

· Tunnel supports

· Supports for storage containers

· Airport facilities such as runway and aprons

· Roads and bridge structures

· Concrete slabs

· Power plant facilities

· Seismic resistant structures (due to its light weight and shock absorption property

· Architectural features and structures

8. ARCHITECTURAL APPLICATION OF GRP

8.1 Suitability of GFRP for Architectural Application

Modern architecture is an expression of various ideas, thoughts, concepts and realities to fulfill the basic principles of architecture in materials such as

· Strength

· Functional utility

· Aesthetics

Modern architecture has improved with the invention of new materials and new techniques. GFRP is an attractive material for both construction and architecture .it has limitless architectural application in the construction industry. It offers combination of properties net available in any other conventional material.

The selection of any construction material is based on Performance and Systematic approach

Performance requirements of a material can be defined as an expected level of performance in order to fulfill a given function. For this various attributes like structural serviceability, durability, thermal and acoustic properties, compatibility, fire safety, practicability, economy etc should be examined.

Systematic approach is a plan to gather and organize interdependent items of information for decision-making process.

Performance requirements of GFRP can be examined under the following properties

· Can be fabricated in any form and architectural design.

· Offers inherent pigmentation, coating and painting.

· Light transmission property with strong enclosure.

· Surface of GFRP can be treated to get aesthetic importance and fire resistance.

· It has maximum freedom of design as the constituents of GFRP have no inherent shape and hence it is possible to make use of efficient structural shapes and appearance requiring minimum of material for maximum strength and stiffness

· It has high strength, durability and dimensional stability.

· Better resistance to discolouration, weathering and corrosion.

· Fastened joined and replaced

Architectural aesthetics is an additional feature of GFRP with out any damage to the original shape, appearance and strength. It fulfills the following objectives for better architectural applications:

· Attractive eye appeal.

· Improved functional which include resistance to wear, scratching and marring

· Product identification and information by trade marking, lettering and numerals

· Raised or depressed designs with paint and lacquer provide more decorative effects

· Decorative overlays provide contrast and novelty

· Use of additives enhances aesthetics and increased resistance to heat, light, chemical and electrical exposure.

8.2 Techniques for Architectural Application

GFRP gives a variety of surface finishes, shape, size and colour. It provides considerable scope for designers to take due considerations for architectural treatments of GFRP such as

· Material selection

· Moulding process

· Section thickness

· Provision for fastening and joining

The techniques for application of GFRP are

8.2.1. Pigments and Dyes

Polyester and epoxy resins system can be coloured with transparent dyes or pigments. Transparent dyes are normally dissolved in suitable solvent and added to the resin system. Pigments are available in powders and dispersion forms for both polyester resin, epoxy resin etc.

Pigment pastes are prepared by dispersing the powder pigment in suitable resin. Thus GFRP components can be manufactured in wide varieties of colour shades, textures, tones etc. to meet the various aesthetic requirements.

8.2.2. Spray Painting

GFRP surfaces can be coated by spray painting. Coating consists of enamels and lacquers. The enamels are coating containing thermosetting resins dissolved in solvents. Enamels have good properties of high gloss and hardness. Resins such as epoxies and polyurethane’s have been used in making enamels

Figure 1. Spray Painting by Stationary Gun and Movable Part

8.2.3. Vacuum Metallising

It is a process of depositing a thin layer of metal onto a plastic surface by vapourising the metallic filaments (usually pure aluminium) and condensing it while under a high vaccum.Various metal films including silver, gold, nickel, chromium, and aluminium can be used to metallise plastic surfaces. Almost any plastic can be metallised, provided a suitable base coating system is available that will adhere to the plastic part and will accept the metallic film GFRP can be metallised because polyester and epoxy resins can be easily metallised. It is done in a vacuum metallising chamber where aluminium staples are hung on tungsten wire filaments in the center of the chamber.

The filaments temperature is raised up to 982 ˚ C by electric power source and the chamber is then vacuumed. Increase in temperature flashes the molten aluminium from the filament and condense on all the surfaces of the plastic parts. The plastic parts are rotated to ensure complete metal coverage. The complete cycle takes only 15 minutes

Figure 2. Vacuum metallising plastic part

8.2.4. Silk Screen Decorating

It is the process used to force paint or ink through a stencil fabric (i.e. silk screen) on to the plastic that is to be decorated. It consist of a rectangular frame

Figure 3. Silk Screening on a Plastic Surface

marked with a stencil in such a way that allows the paint to be pressed through the screen only where the stencil is open. The screen is placed above the plastic to be decorated and a flexible rubber squeeze the paint link through the opening in the screen to the surface. It can be done on flat and curved surface.

8.3 Architectural Applications

8.3.1. Roofing Sheets

Roofing sheets similar to corrugated asbestos and steel sheets in various designs, colours, textures etc. can be made using GFRP.GFRP flat sheets can be used as false ceilings to provide better aesthetic and eye appeal feeling. Its light transmission characteristics help to use GFRP for lighting purpose in the form of translucent GFRP roof sheets.

8.3.2. Out Door Landscape Elements

Out door land scape elements such as lamp post, benches, chairs, colourful boards, statues, sign boards etc can be made in various colours and designs. They have functional, structural and aesthetic importance. Chairs and benches in stadium, auditorium, airport lounge, lobby seat, bar stool, bathing stool

8.3.3. Partition and paneling

GFRP fancy sheets can be used for partition walls and panelings inside the buildings. They can be used in walls and floors of swimming pools. Side walls of green house can be made of GFRP sheets. They can be easily machined, bolted and riveted.

8.3.4. Ventilation and ducting pipes

Glass fibres and vinyl ester by using filament winding technique are used in the fabrication of ventilating and ducting pipes. It can withstand corrosive condition and retain properties even at high temperature.

8.3.5. Lighting as a decorative tool

Major use of GFRP is the roof lighting sheeting which provides better working environment and savings on power. Thinner section of GFRP products can transmit great deal of light. GFRP is used for dome lights in flat. Colour panels and vertical lighting on buildings. They provide strong enclosure with adequate amount of light transmission.

8.3.6. Cladding

GFRP is used for cladding other structural materials or as an integral part of either a structural or non load bearing wall panel, for cladding structures of concrete or brick flat sheets can be used. The advantages of GFRP here are the ease of fabricating large panels to minimum joints and the infinite range of coloured and textured surface.

8.3.7. Decorated GFRP plates

GFRP can be molded with raised on depressed design with paints or enamels. This type of GFRP plates can be used for any decorative purpose.

8.3.8. Sanitary ware

Wash basins, cisterns, bath tubs are made by press moulding or contact moulding techniques. The advantages are its light weight and minimum maintenance, stain resistance and longevity of the product.

8.3.9. Doors and windows

Light weight GFRP doors are use for office cabins and residential application.

The advantages of GFRP doors over conventional doors are

· 100 % weather, water, moisture and rot proof.

· available in eye catching colours

· good dimensional stability

· zero maintenance

· ready to use

· stains, if any can washed

8.4. Examples of architectural application:

8.4.1. Dome architectural design

The Domes in enchanting shapes and unique design with wide dimension can be created for eye catching aesthetics. GFRP can provide good finishes. A self supporting dome with a diameter of 14m and a height of 8m has been made of GFRP for a new mosque in Leichester, UK.GFRP is increasingly favoured for dome construction as moulds can be large and have intricate part decoration included.

8.4.2. Scrubbing tower

A scrubbing tower by using various component of GFRP is fabricated by the coromandel Pvt Ltd, Chennai. Glass fibres and vinyl resin have been used by hand lay up technique to manufacture GFRP. It is the largest scrubber in India with out any steel reinforcement.

8.4.3. Structure of Dubai airport

Structures of Dubai airport is a typical example of GFRP construction for achieving the complex architectural structures. Road side telephone booths, traffic control stands, towers, shops, mobile bathrooms, toilets, etc are recent construction using GFRP. These structures have aesthetics and functional importance.

9. APPLICATION OF GFRP IN OTHER ENGINEERING FIELDS:

9.1. Marine field

Used in high speed boats, naval vessels, high capacity trawlers, barges and in other ship components.

9.2. In transportation sector

Used in automobiles due to its lighter weight, durability, and corrosion resistance.

9.3. In chemical industry

Supplemented by the advantages like light weight, mouldability, fire resistance property. The resistance to chemicals made the material popular in chemical industry.

9.4. Electrical and electronics field

The glass fibre mainly E glass having high electrical insulating property made it useful in the construction of distribution pillar, link boxes, profiles, separation of current carrying phases to prevent short circuiting.

10.0 CONCLUSIONS

The building construction industry is an important sector as user of GFRP. It has proved to be the fastest growing market for GFRP products in the last 10 years due to its increased application in various fields. The use of composite material in concrete repair industry has attracted much attention. The benefits offered by the new technique have out weighted its disadvantages.

In this century the role of internet, electronic and print media has brought the knowledge at the door step. In spite of that it is necessary to create awareness among the users, architects, engineers etc. regarding the utilization of GFRP both as architectural and construction material. It is costlier than the conventional method, but is economical in long run, if further investigation is done in proper selection of reinforcement and matrix material, fabrication treatment techniques, design of components etc.

ACKNOWLEDGEMENT

I express my sincere gratitude to my seminar guide Smt. UMADEVI P.P Senior lecturer, Department of Civil Engineering, without whose valuable guidance and support the seminar would not have been a success.

I thank Prof. T. DIVAKARAN, Head of the Department of Civil Engineering for the good will and encouragement extended to me.

Last but not the least I thank almighty, for giving me the strength and power to complete this project on time.

REFERENCES

1. A. J. Leggatt, “GRP And Buildings”, The Structural Engineer. Vol. No: 12. December 1970.

2. HON.Y and Yogesh Chhabbra. “Use Of Glass Fibre Reinforced Plastic For Structural Strengthening Of Reinforced Concrete”, ICJ April 1999.

3. Pawan Kumar and A. K. Shrivastava, “Architectural Application of GFRP, IE (I) Journal Vol.82. March 2002.

4. S. Sundaram and Sridar, “Glass Fibre Reinforced Plastic in Building Construction”, Civil Engineering and Construction Review. Vol. 12 No: 9. September 1999.

5. www.support @ cyb_glass fibre. Co.uk

6. www.icjonline .com “Indian Concrete Journal March 2003