1. No category

Advanced Continuous Tow Shearing
for next generation AFP technology
Dr Byung Chul (Eric) Kim
 B.C.Eric.Kim@bristol.ac.uk
Complex geometry and Fibre steering
In-situ impregnation
Fibre steering technology is essential to
manufacture complex composite parts. Even
when the geometry is simple and developable,
fibre paths sometimes need to be steered to
avoid gaps and overlaps or to achieve designed
fibre angle distribution with non-geodesic paths.
As the complexity increases (e.g. doubly-curved
surfaces), the geodesic paths deviate more from
the designed fibre paths so that tighter steering
radii are required.
The built-in online impregnation device can produce a partially
impregnated tow just before it is laid down. The produced tow has dry
fibres on the top surface to allow the compaction shoe to slide on it
and a sticky surface on the bottom for secure placement. Vertically
distributed void areas provide sufficient fibre binding force along the
thickness direction as well as in-plane shear flexibility.
< Void distribution in a commercial prepreg (left) and the tow produced by in-situ impregnation (right) >
Current technology and its limitation
All existing fibre steering technologies (e.g. AFP, TFP) consider a tow as
a narrow tape and apply in-plane bending deformation to lay up a
curved path. This way of handling tow materials always produce defects
such as fibre buckling, overlaps and resin pockets. Generally the
minimum steering radius is limited to 0.5-0.6 m to minimise the
defects. However, overlaps and gaps cannot be avoided.
Fibre buckling
Tow gaps
ACTS (Advanced CTS) for 3D complex geometries
For applying the steering capability of CTS to 3D complex geometries, 2
advanced functions should be added. Since the flat compaction shoe
cannot conform with a convex or concave surface, a conformable
compaction device with non-stick property is required. More importantly,
since the surface cannot be tessellated by strips with a fixed width, the
head needs to be able to adjust the tow width.
Tow overlaps
Tow overlap
Game-changing fibre steering technology
: Continuous Tow Shearing
Impregnation
device
AFP
Controllability
of tow width
AFP
Tow drop
Resin tape
Target capability
of ACTS
Conformable compaction shoe for contoured
surface
CTS
CTS steers the fibre path by
applying in-plane shear deformation
to a semi-impregnated tow which is
supplied continuously. By changing
the fundamentals of fibre placement,
it can minimise fibre buckling and
reduce the minimum steering radius
by an order of magnitude over the
AFPs.
Compaction
device with
high surface
conformity
Tape take-up roller
Tow feeding roller
Compaction
shoe
Compaction shoe with an inflatable flexible tubing on its surface.
- Provide a rigid edge boundary for shearing the tow material
- Conformable with the uneven surface generated by tow thickness
change (Tow thickness: 0.13 ~ 0.5 mm (0° ~ 75° of shear angle))
- Have non-stick property on the tow surface
Gripping shoe
dx < 1 mm
CTS
CT scan result
Steering R: 40~100mm
< Convex surface >
Surface R of curvature: 80 mm
< Concave surface >
Surface R of curvature: 80 mm
Impacts and Potential applications
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Smooth surface without
tow overlaps and gaps
Steering R: 50mm
Steering R: 150~700mm)
Photoed by Dr. Nagelsmit and Dr.
Gerrits of the NLR
Steering R: 150mm
High-quality composite products with complex geometries
Automated layup head with low cost and simple mechanism
Flexibility in selection of fibre and resin types
More flexibility in design - exceptionally small steering radius
Simplification of structural analysis without consideration of processinduced defects
• Potential applications: Composite fan and turbine blades, Add-on
module for AFP heads, In-house prepreg production