186
7
processes with low investment costs but a high degree of manual
handling. Virtually all types of reinforcement can be used in open
moulding. Together with the use of core materials, the reinforcement may be used to create sandwich structures, enabling access to
the widest range of mechanical and structural performance of any
composite process.
In contact layup, the major limitation is the low-dimensional
accuracies and use of only room-temperature curable resins. More
often, the mechanical properties obtained are poor. Thus, contact
layup is not used for high-end applications requiring more of a
load. Unsaturated polyester resins dominate in this area, but epoxy
and vinyl ester resins are also common for load-bearing composites. Spray lamination is very similar to the hand layup process, as
discussed previously. This lamination process is much easier and
faster than a hand layup and can be automated using automatic
robotic spray guns. The major limitation is the control of volume
fractions of the reinforcement where usually the volume fraction of
the reinforcement remains at the lower side.
7.1.3 Filament Winding Technology
5 Processing Technology—Filament winding is a process which is
used for fabrication of cylindrical composite structure for
high-pressure applications. It is an automated open moulding
process that uses a rotating mandrel as the mould. The filament
winding process is mostly used for thermosetting resins. In this
process, roving of glass or aramid fibres or tows of carbon fibres
are first impregnated in the resin bath and then passed through
the nip roller in order to remove the excess resin. This impregnated roving or tow is wound over a mandrel under a specific
tension on a geodesic path. The geodesic path is a firm path on
a curved surface on which no lateral movement or slippage of
fibre rovings or tows is allowed [11, 12]. A schematic of the
filament winding process is shown in . Fig. 7.4. The laying of
the roving or tow is controlled by a three to ten axes of the
machine. The most important axes of control are movement of
the carriage; movement of the payout eye, which lays the roving
on the mandrel; rotation of the mandrel; movement of the nip
rollers; and tension in the roving/tow.
The rocket motor of a spacecraft only can be made using
filament winding or polar winding technology out of carbon or
Kevlar fibres as the reinforcement and epoxy or phenolic resin
as the matrix systems. The filament winding process is found
most suitable for making composite pressure vessels, such as a
rocket motor. However, a variant of the filament winding
process is the tape winding process, which is presently used for
the manufacturing of large-sized pressure vessels due to its fast
processing time.
In the filament winding process, the mandrel acts as a male
mould. This produces a finished inner surface and a laminated
rough surface in composites. Filament winding results in a
Point to Ponder…
Geodesic path is a shortest path
between two vertices. Generally,
filament winding is carried out on a
geodesic path. Non-geodesic path
filament winding requires high
tackiness of the resin and special
processing features for fibre tension
and holding.
Chapter 7 · Processability in Open Mould Processing of Polymeric Composites
7
processes with low investment costs but a high degree of manual
handling. Virtually all types of reinforcement can be used in open
moulding. Together with the use of core materials, the reinforcement may be used to create sandwich structures, enabling access to
the widest range of mechanical and structural performance of any
composite process.
In contact layup, the major limitation is the low-dimensional
accuracies and use of only room-temperature curable resins. More
often, the mechanical properties obtained are poor. Thus, contact
layup is not used for high-end applications requiring more of a
load. Unsaturated polyester resins dominate in this area, but epoxy
and vinyl ester resins are also common for load-bearing composites. Spray lamination is very similar to the hand layup process, as
discussed previously. This lamination process is much easier and
faster than a hand layup and can be automated using automatic
robotic spray guns. The major limitation is the control of volume
fractions of the reinforcement where usually the volume fraction of
the reinforcement remains at the lower side.
7.1.3 Filament Winding Technology
5 Processing Technology—Filament winding is a process which is
used for fabrication of cylindrical composite structure for
high-pressure applications. It is an automated open moulding
process that uses a rotating mandrel as the mould. The filament
winding process is mostly used for thermosetting resins. In this
process, roving of glass or aramid fibres or tows of carbon fibres
are first impregnated in the resin bath and then passed through
the nip roller in order to remove the excess resin. This impregnated roving or tow is wound over a mandrel under a specific
tension on a geodesic path. The geodesic path is a firm path on
a curved surface on which no lateral movement or slippage of
fibre rovings or tows is allowed [11, 12]. A schematic of the
filament winding process is shown in . Fig. 7.4. The laying of
the roving or tow is controlled by a three to ten axes of the
machine. The most important axes of control are movement of
the carriage; movement of the payout eye, which lays the roving
on the mandrel; rotation of the mandrel; movement of the nip
rollers; and tension in the roving/tow.
The rocket motor of a spacecraft only can be made using
filament winding or polar winding technology out of carbon or
Kevlar fibres as the reinforcement and epoxy or phenolic resin
as the matrix systems. The filament winding process is found
most suitable for making composite pressure vessels, such as a
rocket motor. However, a variant of the filament winding
process is the tape winding process, which is presently used for
the manufacturing of large-sized pressure vessels due to its fast
processing time.
In the filament winding process, the mandrel acts as a male
mould. This produces a finished inner surface and a laminated
rough surface in composites. Filament winding results in a
Point to Ponder…
Geodesic path is a shortest path
between two vertices. Generally,
filament winding is carried out on a
geodesic path. Non-geodesic path
filament winding requires high
tackiness of the resin and special
processing features for fibre tension
and holding.
Chapter 7 · Processability in Open Mould Processing of Polymeric Composites