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Filament windingFibre placement

Tape layingPultrusion

Tube rolling

Filament winding simple machine: just two axes

rotation of the mandreltranslation of the feed eye on an axis parallel

to the machine axis complexity characterised by

the number of degrees of freedom: up to six separately controlled axesusually three orthogonal and three rotational

axes

Filament winding

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 fibrepart diameterwinding pattern

Filament winding - tension fibre tension directly affects

fibre volume fractionvoid contentand, in turn, influences

the strength and stiffness of the composite part.

difficult to maintain tension on flat surfacesaxial winding not

a preferred orientation on cylinders.

Filament winding - impregnation

resin impregnation

Filament winding - winding patterns hoop (90º) a.k.a girth or circumferential winding

angle is normally just below 90° degreeseach complete rotation of the mandrel shifts the fibre

band to lie alongside the previous band. helical

complete fibre coverage without the bandhaving to lie adjacent to that previously laid.

polardomed ends or spherical componentsfibres constrained by bosses on each pole of the

component. axial (0º)

beware: difficult to maintain fibre tension

Filament winding - winding patterns

hoop : helical:

polar:

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

assumes non-slip winding once winding has commenced,

fixed fibre path at any point dictated by the Clairaut angle ( r.sin a = constant) where r is local radius, a is local angle

at bosses, a = arcsin (rb/r)

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

Filament winding - applications pressure vessels, storage tanks and pipes rocket motors, launch tubes

Light Anti-armour Weapon (LAW)○ Hunting Engineering made a nesting pair in 4

minuteswith ~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 bladeslength 45.7 m, diameter 8.2 m, weight > 36 tonnes.

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

on-line consolidation and cooling permit use without the requirement for the fibre restraints.

Tape laying computer-numerically controlled (CNC)

technique laying prepreg reinforcement tapeCartesian framework for gross positioning

(rather than a primarily rotational axis robot)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)

impregnate with resinpull 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

hand-over-hand hydraulic clampsconveyor belt/caterpillar track systems.

moving cut-off machine ("flying cutter")

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 - 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

a technique where pre-preg isformed onto a tapered mandreland consolidated using shrink-wrap.

most often used to make fishing rod blanks illustrated at

http://www.kilwellfibretube.co.nz/blank-making.html

VACUUM FORMING

Vacuum Forming is a technique that is used to shape a variety of plastics. In school it is used to form/shape thin plastic, usually plastics such as; polythene and perspex. Vacuum forming is used when an unusual shape like a ‘dish’ or a box-like shape is needed. To the right you can see the stages involved in vacuum forming.

STEP 1

STEP 2

STEP 3

STEP 4

STEP 5

STEP 6

STEP 7

First, a former is made from a material such as a soft wood.

The former is placed in the oven and a sheet of plastic (for example, compressed polystyrene) is clamped in position above the mould.

The heater is then turned on and the plastic slowly becomes soft and pliable as it heats up. The plastic can be seen to 'warp' and 'distort' as the surface expands.

After a few minutes the plastic is ready for ‘forming’ as it becomes very flexible.

The heater is turned off and the mould is moved upwards by lifting the lever until it locks in position.

The 'vacuum' is turned on. This pumps out all the air beneath the plastic sheet. Atmospheric pressure above the plastic sheet pushes it down on the mould. When the plastic has cooled sufficiently the vacuum pump is switched off.

The plastic sheet is removed from the vacuum former. The sheet has the shape of the former pressed into its surface.

A flat plastic sheet goes through the vacuum forming process from start to finish.

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