FW: filament windingAFP: automated fibre placementATL: tape laying

pultrusiontube 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 axeso rotation of the mandrelo translation of the feed eye on an axis

parallel to the machine axis

• complexity characterised bythe number of degrees of freedom: o up to six separately controlled axeso usually three orthogonal and three

rotational axes

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 o type of fibreo part diametero winding pattern

Filament winding - tension

• fibre tension directly affectso fibre volume fractiono void contento and, in turn, influences

the strength and stiffness of the composite part.

• difficult to maintain tension on flat surfaceso 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

o angle is normally just below 90° degreeso each complete rotation of the mandrel shifts the

fibre band to lie alongside the previous band.

• helicalo complete fibre coverage without the band

having to lie adjacent to that previously laid.

• polaro domed ends or spherical componentso fibres constrained by bosses on each pole of the

component.

• 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.jpghttp://www.tifac.org.in/news/acfil2.jpghttp://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 patho 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 machineand a continuous curing oven.

• drive shafts• Entec “the world’s largest five-axis filament

winding machine” for wind turbine bladeso length 45.7 m, diameter 8.2 m, weight > 36 tonnes.

AFP: automated fibre placement

• multi-axis robot wet-winds fibrearound 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 tapeo Cartesian framework for gross positioning

(rather than a primarily rotational axis robot)o rotational freedoms close to the work-piece.

• 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)o impregnate with resino pull through a heated die

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

o hand-over-hand hydraulic clampso conveyor belt/caterpillar track systems.

• moving cut-off machine ("flying cutter")

Pultrusionproduction 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 coolingand 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 isformed onto a tapered mandreland consolidated using shrink-wrap.

• most often used to make fishing rod blanks