Transcript Title
FW:
AFP:
ATL:
filament winding
automated fibre placement
tape laying
pultrusion
tube rolling
John Summerscales
Filament winding
• continuous fibre reinforcements are
precisely positioned in a pre-determined
pattern on a rotating mandrel
(mould tool for filament winding)
• normally computer numerically controlled
(CNC) to permit highly automated
production of axisymmetric components
Filament winding
• simple machine: just two axes
rotation of the mandrel
o translation of the feed eye on an axis
parallel to the machine axis
o
• complexity characterised by
the number of degrees of freedom:
up to six separately controlled axes
o usually three orthogonal and three
rotational axes
o
Filament winding
image from http://www.tifac.org.in/news/acfil.jpg
Filament winding - tension
• fibre tension is critical to
the operation of a filament winding machine
• normal to have fibre tensioners
(closed-loop controlled servo-driven "dancers")
• tension required depends on
type of fibre
o part diameter
o winding pattern
o
Filament winding - tension
• fibre tension directly affects
fibre volume fraction
o void content
o and, in turn, influences
the strength and stiffness of the composite part.
o
• difficult to maintain tension on flat surfaces
o
axial winding not
a preferred orientation on cylinders.
Filament winding - impregnation
• resin impregnation
image from http://www.pultrex.com/images/productimages/resin2.jpg
Filament winding - winding patterns
• hoop (90º) a.k.a girth or circumferential winding
angle is normally just below 90° degrees
o each complete rotation of the mandrel shifts the fibre
band to lie alongside the previous band.
o
• helical
o
complete fibre coverage without the band
having to lie adjacent to that previously laid.
• polar
domed ends or spherical components
o fibres constrained by bosses on each pole of the
component.
o
• axial (0º)
o
beware: difficult to maintain fibre tension
Filament winding - winding patterns
hoop:
helical:
polar:
images from:
http://www.tifac.org.in/news/acfil1.jpg
http://www.tifac.org.in/news/acfil2.jpg
http://www.tifac.org.in/news/acfil3.jpg
Filament winding - winding pattern
• Kevlar component
image from http://www.tifac.org.in/news/acfil5.jpg
Filament winding - geodesic path
• simplest fibre orientation is the geodesic path
o
assumes non-slip winding
• once winding has commenced,
fixed fibre path at any point dictated by the
Clairaut angle ( r.sin a = constant)
o
where r is local radius, a is local angle
• at bosses, a = arcsin (rb/r)
o
where rb = angle at the boss (polar opening)
• exploiting friction, it is possible to achieve
non-geodesic winding within limits.
Lattice structures (anisogrid)
• can be produced by partial coverage and
careful choice of relative band positions
image from Vasiliev et al, Composite Structures, 2001, 54(2-3).
• GeoformTM communication masts,
railway gantries, spray booms, etc
Filament winding - applications
• pressure vessels, storage tanks and pipes
• rocket motors, launch tubes
o
Light Anti-armour Weapon (LAW)
Hunting Engineering made a nesting pair in 4 minutes
with ~20 mandrels circulated through the machine
and a continuous curing oven.
• drive shafts
• Entec “the world’s largest five-axis filament
winding machine” for wind turbine blades
o
length 45.7 m, diameter 8.2 m, weight > 36 tonnes.
AFP: automated fibre placement
• multi-axis robot wet-winds fibre
around a series of pins
(or similar restraints within a mould)
in a predetermined pattern.
• not limited by geodesic paths
• used to produce Geoform
(lattice-work with coverage in specific bands)
• better for thermoplastic matrix composites
o
on-line consolidation and cooling permit use
without the requirement for the fibre restraints.
ATL: automated tape laying
• computer-numerically controlled (CNC)
technique laying prepreg reinforcement tape
Cartesian framework for gross positioning
(rather than a primarily rotational axis robot)
o rotational freedoms close to the work-piece.
o
• used for thermoset or thermoplastic matrix
• limited to flat or low curvature surfaces
• high quality aerospace composites
e.g. flight control surfaces and wing skins.
Pultrusion
• continuous constant cross-section profile
• normally thermoset (thermoplastic possible)
impregnate with resin
o pull through a heated die
o
resin shrinkage reduces friction in the die
polyester easier to process than epoxy
• tension control as in filament winding
• post-die, profile air-cooled before gripped
hand-over-hand hydraulic clamps
o conveyor belt/caterpillar track systems.
o
• moving cut-off machine ("flying cutter")
Pultrusion
production of constant cross-section profiles
Image from www.acmanet.org/pic/images/schematic.jpg (no longer online)
Videos: Soc.Mfg.Eng (1’18”) Strongwell (1’32)
Pultrusion - design
• manuals by Quinn and Hartley
• seek uniform thickness
in order to achieve uniform cooling
and hence minimise residual stress.
• hollow profiles require a cantilevered mandrel
to enter the die from the fibre-feed end.
Pultrusion -applications
•
•
•
•
•
•
panels – beams – gratings – ladders
tool handles - ski poles – kites
electrical insulators and enclosures
light poles - hand rails – roll-up doors
450 km of cable trays in the Channel Tunnel
plus ...
Pultrusion (ACCS/Composolite®)
• Advanced Composite Construction System
o
components: plank ............... and connectors
o
used in Aberfeldy and Bonds Mill Lock bridges
Images from .. www.ksci.com/graphics/aberf.gif ..and.. www.stroudwater.co.uk/cpsn/bonds%20mill%20bridge%203.jpg (no longer online)
Pultrusion - variations of process
• pulwinding/pulbraiding:
fibres are wound onto the core of the
pultrusion before it enters the heated die.
• pulforming:
the profile is subjected to post-die shaping.
Tube rolling (mandrel wrapping)
• a technique where pre-preg is
formed onto a tapered mandrel
and consolidated using shrink-wrap.
• most often used to make fishing rod blanks