JEC COMPOSITES MAGAZINE - Issue #146 - June/July 2022 - 27

Filament winding process based on jet engine nozzle geometry for stealth aircraft
a
b
c
The Pitch is in effect a distance of travel
along the spine per rotation of the path
around the part. Having created the path,
the Cadfil software calculate the friction
(anti-slip) requirements of the path so
the user can check it is within acceptable
limits. A set of paths can be created and
combined to make a winding layer and
sets of winding layers can be combined
to make a complete component winding.
Cadfil has a full set of 3D analysis tools
available to look at the geometry, thickness
and 3D motion of the winder.
The paths created can be exported to
CAD, FEM model or used to generate
control data for a wide range of CNC or
robotic winder.
d
with the conventional filament winding
process, it is essential to create an accurate
fibre placement and winding trajectory
through manufacturing (CAD/CAM)
design tools in advance.
Manufacturing of aircraft parts
through filament winding process
In this case study, the dry winding process
was carried out only with carbon fibre in
order to understand the formability of the
shape of the engine exhaust nozzle, and
the optimal winding pattern and angle
setting was required to prevent the fibre
slip in the vicinity of the double serpentine
shape in advance. Optimised process
conditions for executing a successful
filament winding process for non-axisymmetric
shapes could be presented
through a commercial filament winding
simulation tool (Figure 2).
Key strategies for
non-axisymmetric
winding simulation
Cadfil® has several different design
strategies for winding non-standard geometries.
Because this component is primarily
a complex duct (a multi-curved
tube of a variable section) a method
based on using helical paths generated
relative to a curved spine was used. This
is analogous to winding a helix relative
e
Fig. 2: Winding pattern simulation results with 3D graphic viewer (Courtesy of Cadfil)
to the axis of a normal round pipe whose
axis is a straight line. A brief summary of
the process of creating a winding path in
Cadfil follows.
First in CAD the part must be orientated
as it would be presented to the winding
machine so that the X axis of the part is
the mandrel rotation axis. The Second
step is to create spine curves to investigate.
Figure 2a shows the part geometry
and a couple of spine curves. The red
curve was the initial design, and the
blue curve is a small modification that
allowed a slightly greater winding extent
at the large diameter end. The mandrel
surface geometry is exported from CAD
as a triangulated mesh via FEA or 3D
print formats. Cadfil supports several
standard data formats. The curve geometries
were exported as standard STEP
data and are fully general composite
curves made up of line, arc or complex
splines.
The next step is a user dialog to create
a set of data parameters for a winding
path. The parameters include the surface
geometry file, the step file and curve
picked, the extent of the spine curve to
use (trimming), the initial orientation
of the start and importantly the Helical
pitch of the winding.
The ultimate goal of this study is to
use highly priced SiC fibre through the
winding process to manufacture the
exhaust nozzles on the outermost layer
that are exposed to high temperatures.
Therefore, the minimum amount of SiC
fibre could be used by setting the bandto-band
distance (pitch) to be more than
one fibre band width when designing
the winding pattern (Figure 2a). To fill
the gap between the bands, set the start
position of the second circuit to a point
shifted by 10mm from the start position
of the first circuit (Figure 2b).
It can be seen in Figure 2 c that all the
gaps are filled when the circuit is repeated
6 times in total.
As shown in Figure 2d, it was predicted
that the fibre would gather at the beginning
of the curved part, but a uniform
thickness distribution would be formed
in other regions.
The collision between the machine and
the mandrel during the winding process
can be predicted through the 3D graphic
viewer (Figure 2 e), and in this case, the
machine's movement was not disturbed
by the mandrel.
A relatively inexpensive carbon fibre
bundle was used to optimise the winding
process conditions.
In the actual process, it was expected
that the fibre slip would occur finely
along the curved surface.
N°146 June - July 2022 / jec composites magazine
27
JEC COMPOSITES MAGAZINE - Issue #146 - June/July 2022

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