Glass-reinforced plastic
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Glass-reinforced plastic (GRP), is a composite material or fiber-reinforced plastic made of a plastic reinforced by fine fibers made of glass. Like graphite-reinforced plastic, the composite material is commonly referred to by the name of its reinforcing fibers (fiberglass). The plastic is thermosetting, most often polyester or vinylester, but other plastics, like epoxy (GRE), are also used. The glass is mostly in the form of chopped strand mat (CSM), but woven fabrics are also used.
As with many other composite materials (such as reinforced concrete), the two materials act together, each overcoming the deficits of the other. Whereas the plastic resins are strong in compressive loading and relatively weak in tensile strength, the glass fibers are very strong in tension but have no strength against compression. By combining the two materials together, GRP becomes a material that resists well both compressive and tensile forces. The two materials may be used uniformly or the glass may be specifically placed in those portions of the structure that will experience tensile loads.
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[edit] Applications
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, although its use there is 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.
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
A wide variety of storage tanks are 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 & dormers, chimneys, coping systems, heads with keystones and cills. 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, underground as well as above.
- Firewater systems
- Cooling water systems
- Drinking water systems
- Waste water systems/Sewage systems
- Gas systems
[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.
- See also: Fiberglass molding
[edit] Examples of GRP use
- Sailplanes, Sports cars, microcars, karts, bodyshells, boats, kayaks, flat roofs, lorries, wind turbine blades.
- Pods, domes and architectural features where a light weight is necessary.
- Bodies for automobiles, such as the Chevrolet Corvette and Pontiac Fiero.
- A320 Radome.
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