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A-Z guide to composites production and fabrication

Bulk Moulding Compound (BMC)

Thermosetting resin (unsaturated polyester or vinyl ester) mixed with glass fibre reinforcement, fillers, and so on, into a compound for compression or injection moulding.

 

Closed Mould

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Continuous Sheet Production

A continuous moulding between layers of film is used in the production of sheets, in flat or profiled (such as corrugated) forms. The main applications are in building (cladding and roofing) and agriculture (greenhouses).

 

Compression Moulding

A technique for moulding thermoset plastics in which a part is shaped by placing the glass/resin compound into an open mould cavity, closing the mould, and applying heat and pressure until the material has cured or achieved its final form.

 

Filament winding

A process for fabricating a composite structure in which continuous reinforcements (filament, wire, yarn, tape, or other), either previously impregnated with a matrix material or impregnated during the winding, are placed over a rotating and removable form or mandrel - usually cylindrical in shape. When the required number of layers is applied, the wound form is cured and the mandrel removed.

 

Hand lay up

An open mould fabrication method in which reinforcement layers are placed in mould by hand, saturated with resin and then cured to the formed shape. This is usually accomplished by rollers or brushes, with an increasing use of nip-roller type impregnators for forcing resin into the fabrics by means of rotating rollers and a bath of resin. Laminates are left to cure under standard atmospheric conditions.

 

Injection Moulding

Method of forming a plastic to the desired shape by forcibly injecting the polymer into the mould.

 

Open Mould

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Reinforced Reaction Injection Moulding (RRIM)

Two or more reactive liquids are mixed under high pressure together with a solid reinforcing material (eg, glass fibre, mineral fibre, glass beads) and injected into the mould where polymerisation completes to produce the finished composite. RIM is the only plastics process where the chemical reaction takes place in the mould. The polymer matrix is usually a thermosetting polyurethane (PU).

 

Pultrusion

An automated, continuous process for manufacturing composite rods, tubes and structural shapes having a constant cross section. Roving and other reinforcements are saturated with resin and continuously pulled through a heated die, where the part is formed and cured. The cured part is then cut to length.

 

Resin Transfer Moulding (RTM)

A moulding process in which catalyzed resin is transferred into an enclosed mould into which the fibre reinforcement has been placed; cure normally is accomplished without external heat. RTM combines relatively low tooling and equipment costs with the ability to mould large structural parts.

 

Sheet Moulding Compound (SMC)

A ready-to-mould glass fibre reinforced polyester material primarily used in compression moulding using matched metal tools. SMC production can be divided into two processes – the SMC prepreg production and the SMC compression moulding.

 

Spray-Up

An open mould technique in which fibrous glass and resin is simultaneously deposited in a mould. The roving is fed through a chopper and ejected into a resin stream, which is directed at the mould by a spray gun system.

 

Thermoplastic Compounding

Plastics preparations based on thermoplastic polymers in the form of granules, or pellets ready for processing by injection moulding etc. Depending on the intended use, stabilizers, fillers, pigments, reinforcing agents, etc. can be added to the basic resin.

 

Vacuum Moulding

A process in which a sheet of flexible transparent material plus bleeder cloth and release film are placed over the lay-up on the mould and sealed at the edges. A vacuum is applied between the sheet and the lay-up. The entrapped air is mechanically worked out of the lay-up and removed by the vacuum, and the part is cured with temperature, pressure, and time.