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This
process is primarily used for hollow, generally
circular or oval sectioned components, such
as pipes and tanks. Fibre tows are passed through
a resin bath before being wound onto a mandrel
in a variety of orientations, controlled by
the fibre feeding mechanism, and rate of rotation
of the mandrel.
While filament
winding machine design varies with part geometry,
the basic filament winding process concept is
described in the following schematic.
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The fibres are impregnated with resin (by immersion,
or by passing over a resin-wetted drum, or by
injection into the die) before being led to
a feed eye where a controlled band-width is
set prior to positioning on the mandrel.
Fiber tension is critical to the operation of
a filament winding machine. The fibers are supplied
on creels and it is normal to have fiber tensioners
(closed-loop controlled servo-driven "dancers")
in the feed line. The tension required is dependent
on the type of fibre, the part diameter and
the winding pattern selected. The tension directly
affects both fibre volume fraction and void
content and, in turn, influences the strength
and stiffness of the composite part.
Once the fiber package is
positioned the resin is taken to full cure,
often by heating in an oven. The final stage
is mandrel removal to leave the desired hollow
component. This may be achieved by hydraulic
rams for extracting steel mandrels. For more
complex structures, the mandrel may be a low
melting point materials (eg metal alloy) or
a water soluble salt (leachable plaster) which
can be washed out or a collapsible rubber
or a non re-useable foam. In some cases, where
a liner is required for minimal gas permeability
the liner may also function as the mandrel
and hence not need to be removed.
Filament winding has been
combined with other fiber application methods
such as hand layup, pultrusion, and braiding.
Classic filament winding involves a spindle
with a carriage or carriages to apply hoop
and helical fibers. Compaction is through
fiber tension. Resin content is now primarily
metered. The machines are generally all computer
controlled with up to six axes independently
monitored. The additional axis comes into
play at the fiber turn-arounds. The extra
head axis allows for better placement of the
band, and more uniform band width.
Materials
Options:
Resins: Any, e.g. epoxy, polyester, vinylester,
phenolic.
Fibers: Glass, aramid, carbon and boron
fibers . The fibers are used straight
from a creel and not woven or stitched
into a fabric form.
Cores: Any, although components are usually
single skin.
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Typical
Applications:
Chemical storage tanks and pipelines,
gas cylinders, rocket motors, launch tubes,
pressure vessels, drive shafts and fishing
rods and missile cases |
Back to Top
Reference:
netcomposites
and John
Summerscales
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