Hand Lay-Up/Spary Lay Up
Usually involves impregnation of glass fibre mat with a liquid polyester mix.
Hand Lay-up is a method of producing composite structures by hand applying
composite materials in successive layers on a tool or mould that defines the
part geometry. Spray lay up is essentially a variant on this process that
involves spraying the matetial into the mould. A 'Gel Coat' can be
incorporated provides a good surface on the mould side.
Compression Moulding
Compression Moulding is perhaps the next most common technique for moulding
thermosets. Compound or blend is placed in mould and heated under
pressure within the platens of a steam-heated press. When reaction is complete,
product is cooled and ejected. Compression moulding is a batch, as
opposed to continuous process. Press moulding Material is charged to a large
press with flat platens, generally in the form of a 'pre-preg'. Heat and
pressure are applied to react the mixture and convert it into the finished
product. This technique is used for large mouldings and some sheet
products. As with compression moulding, this is a rather slow process.
Resin Transfer Moulding
The molten resin is transferred by pressure from a meltpot into a mould, which
is at a temperature above the meltpoint of the resin. This higher temperature
is important for the filling of moulds with high flow length, high wall
thickness ratios and to allow for shrinkage compensation.
Pultrusion
Pultrusion is a continuous process for
manufacturing composites in rods, tubes and structural shapes having constant
cross sections. After the reinforcement is passed through the
resin-impregnation bath, it is drawn through a shaping die to form the desired
cross section ; curing takes place before the laminate can depart from the
cross section.
Filament Winding
Is a continuous, automated fabrication method
that can be highly automated and repeatable with relatively low material costs.
A long, cylindrical tool called a mandrel is suspended horizontally between end
supports, while the "head" - the fibre application instrument - moves
back and forth along the length of the mandrel as it rotates on the horizontal
axis, placing fibre onto the tool in a predetermined configuration. In most
applications, the filament winding apparatus passes the fibre material through a
resin "bath," just before the material touches the mandrel. This is
called "wet winding." Towpreg - continuous fiber pre-impregnated with
resin - also can be wound, eliminating the need for an on-site resin bath. In a
slightly different process, fiber is wound without resin ("dry
winding"). The dry shape is then removed and used as a preform in another
moulding process, such as resin transfer molding (RTM).
Reaction Injection Moulding
These procedures produce polymers made by
reaction during moulding such as polyamides (thermoplastics) or polyurethanes,
unsaturated polyesters, epoxies and phenolics (thermosets). RIM can be done
using injection or transfer moulding.
Injection Moulding
Injection Moulding of thermosets Basically
this is the same process as used for thermoplastics, modified to avoid
hardening of the plastic in the machine. The materials used are widely known as
Dough or Bulk Moulding Compounds (DMC or BMC). In sheet form they are known as
Sheet Moulding Compound (SMC) Applications include electrical switch and fuse
boxes, domestic electrical equipment, microwave containers and tableware. It is
also used for business machine housings, gas and electricity meter housing and
dish aerials.