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7
The fabrication of thermoplastic composites needs special attention due to their high viscosities, high surface tension, inertness,
etc., whereas thermosetting resins have low surface tension and
good reactivity. Composite manufacturing processes may be
divided into two types: open moulding and closed moulding. The
processes in open moulding are contact layup, spray layup, filament
winding, automated tape winding, and casting. With open moulding, the laminate is exposed to the atmosphere during the fabrication process [1–3]. The following are a variety of processing
methods within the open and closed moulding categories.
7.1 Open Mould Processing Technologies
Open moulding processes are those where the part being manufactured is exposed to the atmosphere. The composite part is typically
handled manually. The open moulding process involves saturating
the fibre reinforcement with resin using manual roll-out techniques
to consolidate the laminate and remove any entrapped air. In the
open moulding process, no closed mould or external pressure is
applied. A major factor in this operation is the transfer of resin from
a drum or storage tank to the mould. The resin mixture may be a
liquid being formed onto a reinforcing material, or it may be in the
form of a prepreg material being formed for the final cure [4, 5].
7.1.1 Contact Layup
5 Processing Technology—Contact layup (also known as hand layup
or wet layup) is one of the earliest processing techniques used for
the fabrication of composites. In this batch process technology,
reinforcement in the form of fabric or chopped strand mat
(CSM) is used, and the matrices are room- temperature curable
thermosetting resins, such as polyester resins and epoxy resins.
An open mould is used to fabricate the product, and the outer
surface of the composite product is governed by the finish of the
inner surface of the mould, as shown in . Fig. 7.1.
The open moulds are usually made out of wood, plaster of
paris, composites, or steel, depending on the durability of the
mould required. During moulding, first a release agent (such as
wax polish or a PVA solution) is applied. Then a layer of
high-viscosity resin, which is called gel coat, is applied on the
mould in order to achieve the glossy finish of the product.
Room-temperature (RT) curable resin is applied on every layer
of preform sequentially. Layer after layer of preform is placed
over the mould until the desired thickness of composite is
achieved. The resin is applied using a brush and a roller. After
the curing is complete, the product is ummoulded. This
method is simple and easy to handle, but it is labour-intensive
and not amenable to high production rates. This process does
provide a good surface finish on one surface (i.e. moulding
surface). The drawback of this technology is that the quality of
7.1 · Open Mould Processing Technologies
7
The fabrication of thermoplastic composites needs special attention due to their high viscosities, high surface tension, inertness,
etc., whereas thermosetting resins have low surface tension and
good reactivity. Composite manufacturing processes may be
divided into two types: open moulding and closed moulding. The
processes in open moulding are contact layup, spray layup, filament
winding, automated tape winding, and casting. With open moulding, the laminate is exposed to the atmosphere during the fabrication process [1–3]. The following are a variety of processing
methods within the open and closed moulding categories.
7.1 Open Mould Processing Technologies
Open moulding processes are those where the part being manufactured is exposed to the atmosphere. The composite part is typically
handled manually. The open moulding process involves saturating
the fibre reinforcement with resin using manual roll-out techniques
to consolidate the laminate and remove any entrapped air. In the
open moulding process, no closed mould or external pressure is
applied. A major factor in this operation is the transfer of resin from
a drum or storage tank to the mould. The resin mixture may be a
liquid being formed onto a reinforcing material, or it may be in the
form of a prepreg material being formed for the final cure [4, 5].
7.1.1 Contact Layup
5 Processing Technology—Contact layup (also known as hand layup
or wet layup) is one of the earliest processing techniques used for
the fabrication of composites. In this batch process technology,
reinforcement in the form of fabric or chopped strand mat
(CSM) is used, and the matrices are room- temperature curable
thermosetting resins, such as polyester resins and epoxy resins.
An open mould is used to fabricate the product, and the outer
surface of the composite product is governed by the finish of the
inner surface of the mould, as shown in . Fig. 7.1.
The open moulds are usually made out of wood, plaster of
paris, composites, or steel, depending on the durability of the
mould required. During moulding, first a release agent (such as
wax polish or a PVA solution) is applied. Then a layer of
high-viscosity resin, which is called gel coat, is applied on the
mould in order to achieve the glossy finish of the product.
Room-temperature (RT) curable resin is applied on every layer
of preform sequentially. Layer after layer of preform is placed
over the mould until the desired thickness of composite is
achieved. The resin is applied using a brush and a roller. After
the curing is complete, the product is ummoulded. This
method is simple and easy to handle, but it is labour-intensive
and not amenable to high production rates. This process does
provide a good surface finish on one surface (i.e. moulding
surface). The drawback of this technology is that the quality of
7.1 · Open Mould Processing Technologies