Glass-reinforced plasticFrom Wikipedia, the free encyclopedia

For fibers of glass also known as fiberglass, see glass (fiber).

Glass-reinforced plastic (GRP),[1] also known as glass fiber-reinforced plastic (GFRP),[2] is a fiber

reinforced polymer made of a plastic matrix reinforced by fine fibers made of glass. It is also known

as GFK (for Glasfaserverstärkter Kunststoff), or simply by the name of the reinforcing fibers

themselves: fiberglass.

GRP is a lightweight, strong material with many uses, including boats, automobiles, water tanks, roofing, pipes,

cladding and external door skins.

The plastic matrix may be epoxy, a thermosetting plastic (most often polyester or vinylester) or thermoplastic.

[edit]Production

The manufacturing process for GRP fiber glass uses large furnaces to gradually melt the sand/chemical mix to

liquid form, then extrude it through bundles of very small orifices (typically 17-25 micrometres in diameter for E-

Glass, 9 micrometres for S-Glass). These filaments are then sized with a chemical solution. The individual

filaments are now bundled together in large numbers to provide a roving. The diameter of the filaments, as well

as the number of filaments in the roving determine its weight. This is typically expressed in yield-yards per

pound (how many yards of fiber in one pound of material, thus a smaller number means a heavier roving,

example of standard yields are 225yield, 450yield, 675yield) or in tex-grams per km (how many grams 1 km of

roving weighs, this is inverted from yield, thus a smaller number means a lighter roving, examples of standard

tex are 750tex, 1100tex, 2200tex).

These rovings are then either used directly in a composite application such as pultrusion, filament

winding (pipe), gun roving (automated gun chops the glass into small lengths and drops it into a jet of resin,

projected onto the surface of a mold), or used in an intermediary step, to manufacture fabrics such as chopped

strand mat (CSM) (made of randomly oriented small cut lengths of fiber all bonded together), woven fabrics,

knit fabrics or uni-directional fabrics.

[edit]Sizing

A sort of coating, or primer, which both helps protect the glass filaments for processing/manipulation as well as

ensure proper bonding to the resin matrix, thus allowing for transfer of shear loads from the glass fibers (which

would buckle) to the thermoset plastic (which is quite good at handling shear loads), without this 'bonding', the

fibers can 'slip' in the matrix and localised failure will ensue.[citation needed]. Usually also the basic material for

making cloth.

[edit]Properties

An individual structural glass fiber is both stiff and strong in tension and compression—that is, along its axis.

Although it might be assumed that the fiber is weak in compression, it is actually only the long aspect ratio of

the fiber which makes it seem so; i.e., because a typical fiber is long and narrow, it buckles easily. On the other

hand, the glass fiber is unstiff and unstrong in shear—that is, across its axis. Therefore if a collection of fibers

can be arranged permanently in a preferred direction within a material, and if the fibers can be prevented from

buckling in compression, then that material will become preferentially strong in that direction.

Furthermore, by laying multiple layers of fiber on top of one another, with each layer oriented in various

preferred directions, the stiffness and strength properties of the overall material can be controlled in an efficient

manner. In the case of glass-reinforced plastic, it is the plastic matrix which permanently constrains the

structural glass fibers to directions chosen by the designer. With chopped strand mat, this directionality is

essentially an entire two dimensional plane; with woven fabrics or unidirectional layers, directionality of stiffness

and strength can be more precisely controlled within the plane.

A glass-reinforced plastic component is typically of a thin "shell" construction, sometimes filled on the inside

with structural foam, as in the case of surfboards. The component may be of nearly arbitrary shape, limited only

by the complexity and tolerances of the mold used for manufacturing the shell.

MaterialSpecific gravity

Tensile strength (MPa)

Compressive strength (MPa)

Polyester resin (unreinforced)[3] 1.28 55 140

Polyester and Chopped Strand Mat Laminate 30% E-glass[3] 1.4 100 150

Polyester and Woven Rovings Laminate 45% E-glass[3] 1.6 250 150

Polyester and Satin Weave Cloth Laminate 55% E-glass[3] 1.7 300 250

Polyester and Continuous Rovings Laminate 70% E-glass[3] 1.9 800 350

E-Glass Epoxy composite[4] 1.99 1,770 (257 ksi) N/A

S-Glass Epoxy composite[4] 1.95 2,358 (342 ksi) N/A

[edit]Applications

GRP is an immensely versatile material which combines lightweight with inherent strength to provide a weather

resistant finish, with a variety of surface texture and an unlimited colour range available.

GRP was developed in the UK during the Second World War as a replacement for the molded plywood used in

aircraft radomes (GRP being transparent to microwaves). Its first main civilian application was for building

of boats, where it gained acceptance in the 1950s. Its use has broadened to the automotive and sport

equipment sectors as well as model aircraft, although its use there is now partly being taken over by carbon

fiber which weighs less per given volume and is stronger both by volume and by weight. GRP uses also

include hot tubs, pipes for drinking water and sewers, office plant display containers and flat roof systems.

Advanced manufacturing techniques such as pre-pregs and fiber rovings extend the applications and the

tensile strength possible with fiber-reinforced plastics.

GRP is also used in the telecommunications industry for shrouding the visual appearance of antennas, due to

its RF permeability and low signal attenuation properties. It may also be used to shroud the visual appearance

of other equipment where no signal permeability is required, such as equipment cabinets and steel support

structures, due to the ease with which it can be molded, manufactured and painted to custom designs, to blend

in with existing structures or brickwork. Other uses include sheet form made electrical insulators and other

structural components commonly found in the power industries.

[edit]Storage tanks

Several large GRP tanks at an airport

Storage tanks can be made of GRP with capacities up to about 300 tonnes. The smaller tanks can be made

with chopped strand mat cast over a thermoplastic inner tank which acts as a preform during construction.

Much more reliable tanks are made using woven mat or filament wound fibre with the fibre orientation at right

angles to the hoop stress imposed in the side wall by the contents. They tend to be used for chemical storage

because the plastic liner (often polypropylene) is resistant to a wide range of strong chemicals. GRP tanks are

also used for septic tanks.

[edit]House building

Glass reinforced plastics are also used in the house building market for the production of roofing laminate, door

surrounds, over-door canopies, window canopies and dormers, chimneys, coping systems, heads with

keystones and sills. The use of GRP for these applications provides for a much faster installation and due to

the reduced weight manual handling issues are reduced. With the advent of high volume manufacturing

processes it is possible to construct GRP brick effect panels which can be used in the construction of

composite housing. These panels can be constructed with the appropriate insulation which reduces heat loss.

[edit]Piping

GRP and GRE pipe systems can be used for a variety of applications, above and under the ground.

Firewater systems

Cooling water systems

Drinking water systems

Waste water systems/Sewage systems

Gas systems

[edit]Construction methods

[edit]Fiberglass hand lay-up operation

Resin is mixed with a catalyst or hardener if working with epoxy, otherwise it will not cure (harden) for days/

weeks. Next, the mold is wetted out with the mixture. The sheets of fiberglass are placed over the mold and

rolled down into the mold using steel rollers. The material must be securely attached to the mold, air must not

be trapped in between the fiberglass and the mold. Additional resin is applied and possibly additional sheets of

fiberglass. Rollers are used to make sure the resin is between all the layers, the glass is wetted throughout the

entire thickness of the laminate, and any air pockets are removed. The work must be done quickly enough to

complete the job before the resin starts to cure. Various curing times can be achieved by altering the amount of

catalyst employed.

[edit]Fiberglass spray lay-up operation

The fiberglass spray lay-up process is similar to the hand lay-up process but the difference comes from the

application of the fiber and resin material to the mold. Spray-up is an open-molding composites fabrication

process where resin and reinforcements are sprayed onto a mold. The resin and glass may be applied

separately or simultaneously "chopped" in a combined stream from a chopper gun. Workers roll out the spray-

up to compact the laminate. Wood, foam or other core material may then be added, and a secondary spray-up

layer imbeds the core between the laminates. The part is then cured, cooled and removed from the reusable

mold.

[edit]Pultrusion operation

Diagram of the pultrusion process.

Pultrusion is a manufacturing method used to make strong light weight composite materials, in this case

fiberglass. Fibers (the glass material) are pulled from spools through a device that coats them with a resin.

They are then typically heat treated and cut to length.[5] Pultrusions can be made in a variety of shapes or

cross-sections such as a W or S cross-section. The word pultrusion describes the method of moving the fibers

through the machinery. It is pulled through using either a hand over hand method or a continuous roller

method. This is opposed to an extrusion which would push the material through dies.

[edit]Chopped strand mat

Chopped strand mat or CSM is a form of reinforcement used in glass-reinforced plastic. It consists of glass-

fibers laid randomly across each other and held together by a binder.

It is typically processed using the hand lay-up technique, where sheets of material are placed in a mold and

brushed with resin. Because the binder dissolves in resin, the material easily conforms to different shapes

when wetted out. After the resin cures, the hardened product can be taken from the mold and finished.

Using chopped strand mat gives a glass-reinforced plastic with isotropic in-plane material properties.

[edit]Examples of GRP use

Kayaks made of GRP

Gliders , kit cars, sports cars, microcars, karts, bodyshells, boats, kayaks, flat roofs, lorries, wind

turbine blades.

Minesweeper  hulls

Pods, domes and architectural features where a light weight is necessary.

Bodies for automobiles, such as the Quantum Coupé, Chevrolet Corvette and Studebaker Avanti, and

DeLorean DMC-12 under body.

A320  radome.

FRP tanks and vessels : FRP is used extensively to manufacture chemical equipments and tanks and

vessels. BS4994 is a British standard related to this application.

UHF-broadcasting antennas are often mounted inside a glass-reinforced plastic cylinder on the pinnacle of

a broadcasting tower

Most commercial Velomobiles

ucts are Made

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F IBERGLASS

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BACKGROUND

Fiberglass refers to a group of products made from individual glass fibers combined into a

variety of forms. Glass fibers can be divided into two major groups according to their

geometry: continuous fibers used in yarns and textiles, and the discontinuous (short) fibers

used as batts, blankets, or boards for insulation and filtration. Fiberglass can be formed into

yarn much like wool or cotton, and woven into fabric which is sometimes used for draperies.

Fiberglass textiles are commonly used as a reinforcement material for molded and

laminated plastics. Fiberglass wool, a thick, fluffy material made from discontinuous fibers, is

used for thermal insulation and sound absorption. It is commonly found in ship and

submarine bulkheads and hulls; automobile engine compartments and body panel liners; in

furnaces and air conditioning units; acoustical wall and ceiling panels; and architectural

partitions. Fiberglass can be tailored for specific applications such as Type E (electrical),

used as electrical insulation tape, textiles and reinforcement; Type C (chemical), which has

superior acid resistance, and Type T, for thermal insulation.

Though commercial use of glass fiber is relatively recent, artisans created glass strands for

decorating goblets and vases during the Renaissance. A French physicist, Rene-Antoine

Ferchault de Reaumur, produced textiles decorated with fine glass strands in 1713, and

British inventors duplicated the feat in 1822. A British silk weaver made a glass fabric in

1842, and another inventor, Edward Libbey, exhibited a dress woven of glass at the 1893

Columbian Exposition in Chicago.

Glass wool, a fluffy mass of discontinuous fiber in random lengths, was first produced in

Europe at the turn of the century, using a process that involved drawing fibers from rods

horizontally to a revolving drum. Several decades later, a spinning process was developed

and patented. Glass fiber insulating material was manufactured in Germany during World

War I. Research and development aimed at the industrial production of glass fibers

progressed in the United States in the 1930s, under the direction of two major companies,

the Owens-Illinois Glass Company and Corning Glass Works. These companies developed a

fine, pliable, low-cost glass fiber by drawing molten glass through very fine orifices. In 1938,

these two companies merged to form Owens-Corning Fiberglas Corp. Now simply known as

Owens-Corning, it has become a $3-billion-a-year company, and is a leader in the fiberglass

market.

RAW MATERIALS

The basic raw materials for fiberglass products are a variety of natural minerals and

manufactured chemicals. The major ingredients are silica sand, limestone, and soda ash.

Other ingredients may include calcined alumina, borax, feldspar, nepheline syenite,

magnesite, and kaolin clay, among others. Silica sand is used as the glass former, and soda

ash and limestone help primarily to lower the melting temperature. Other ingredients are

used to improve certain properties, such as borax for chemical resistance. Waste glass, also

called cullet, is also used as a raw material. The raw materials must be carefully weighed in

exact quantities and thoroughly mixed together (called batching) before being melted into

glass.

THE MANUFACTURING PROCESS

MELTING

1 Once the batch is prepared, it is fed into a furnace for melting. The furnace may be

heated by electricity, fossil fuel, or a combination of the two. Temperature must be

precisely controlled to maintain a smooth, steady flow of glass. The molten glass

must be kept at a higher temperature (about 2500°F [1371°C]) than other types of

glass in order to be formed into fiber. Once the glass becomes molten, it is

transferred to the forming equipment via a channel (forehearth) located at the end of

the furnace.

FORMING INTO FIBERS

2 Several different processes are used to form fibers, depending on the type of fiber.

Textile fibers may be formed from molten glass directly from the furnace, or the

molten glass may be fed first to a machine that forms glass marbles of about 0.62

inch (1.6 cm) in diameter. These marbles allow the glass to be inspected visually for

impurities. In both the direct melt and marble melt process, the glass or glass

marbles are fed through electrically heated bushings (also called spinnerets). The

bushing is made of platinum or metal alloy, with anywhere from 200 to 3,000 very

fine orifices. The molten glass passes through the orifices and comes out as fine

filaments.

CONTINUOUS-FILAMENT PROCESS

3 A long, continuous fiber can be produced through the continuous-filament process.

After the glass flows through the holes in the bushing, multiple strands are caught up

on a high-speed winder. The winder revolves at about 2 miles (3 km) a minute, much

faster than the rate of flow from the bushings. The tension pulls out the filaments

while still molten, forming strands a fraction of the diameter of the openings in the

bushing. A chemical binder is applied, which helps keep the fiber from breaking

during later processing. The filament is then wound onto tubes. It can now be twisted

and plied into yarn.

STAPLE-FIBER PROCESS

4 An alternative method is the staplefiber process. As the molten glass flows through

the bushings, jets of air rapidly cool the filaments. The turbulent bursts of air also

break the filaments into lengths of 8-15 inches (20-38 cm). These filaments fall

through a spray of lubricant onto a revolving drum, where they form a thin web. The

web is drawn from the drum and pulled into a continuous strand of loosely assembled

fibers. This strand can be processed into yarn by the same processes used for wool

and cotton.

CHOPPED FIBER

5 Instead of being formed into yarn, the continuous or long-staple strand may be

chopped into short lengths. The strand is mounted on a set of bobbins, called a creel,

and pulled through a machine which chops it into short pieces. The chopped fiber is

formed into mats to which a binder is added. After curing in an oven, the mat is rolled

up. Various weights and thicknesses give products for shingles, built-up roofing, or

decorative mats.

GLASS WOOL

6 The rotary or spinner process is used to make glass wool. In this process, molten

glass from the furnace flows into a cylindrical container having small holes. As the

container spins rapidly, horizontal streams of glass flow out of the holes. The molten

glass streams are converted into fibers by a downward blast of air, hot gas, or both.

The fibers fall onto a conveyor belt, where they interlace with each other in a fleecy

mass. This can be used for insulation, or the wool can be sprayed with a binder,

compressed into the desired thickness, and cured in an oven. The heat sets the

binder, and the resulting product may be a rigid or semi-rigid board, or a flexible

batt.

PROTECTIVE COATINGS

7 In addition to binders, other coatings are required for fiberglass products.

Lubricants are used to reduce fiber abrasion and are either directly sprayed on the

fiber or added into the binder. An anti-static composition is also sometimes sprayed

onto the surface of fiberglass insulation mats during the cooling step. Cooling air

drawn through the mat causes the anti-static agent to penetrate the entire thickness

of the mat. The anti-static agent consists of two ingredients—a material that

minimizes the generation of static electricity, and a material that serves as a

corrosion inhibitor and stabilizer.

Sizing is any coating applied to textile fibers in the forming operation, and may

contain one or more components (lubricants, binders, or coupling agents). Coupling

agents are used on strands that will be used for reinforcing plastics, to strengthen

the bond to the reinforced material.

Sometimes a finishing operation is required to remove these coatings, or to add

another coating. For plastic reinforcements, sizings may be removed with heat or

chemicals and a coupling agent applied. For decorative applications, fabrics must be

heat treated to remove sizings and to set the weave. Dye base coatings are then

applied before dying or printing.

FORMING INTO SHAPES

8 Fiberglass products come in a wide variety of shapes, made using several

processes. For example, fiberglass pipe insulation is wound onto rod-like forms called

mandrels directly from the forming units, prior to curing. The mold forms, in lengths

of 3 feet (91 cm) or less, are then cured in an oven. The cured lengths are then de-

molded lengthwise, and sawn into specified dimensions. Facings are applied if

required, and the product is packaged for shipment.

QUALITY CONTROL

During the production of fiberglass insulation, material is sampled at a number of locations

in the process to maintain quality. These locations include: the mixed batch being fed to the

electric melter; molten glass from the bushing which feeds the fiberizer; glass fiber coming

out of the fiberizer machine; and final cured product emerging from the end of the

production line. The bulk glass and fiber samples are analyzed for chemical composition and

the presence of flaws using sophisticated chemical analyzers and microscopes. Particle size

distribution of the batch material is obtained by passing the material through a number of

different sized sieves. The final product is measured for thickness after packaging according

to specifications. A change in thickness indicates that glass quality is below the standard.

Fiberglass insulation manufacturers also use a variety of standardized test procedures to

measure, adjust, and optimize product acoustical resistance, sound absorption, and sound

barrier performance. The acoustical properties can be controlled by adjusting such

production variables as fiber diameter, bulk density, thickness, and binder content. A similar

approach is used to control thermal properties