Composites Manufacture

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Composites Manufacture

• There are no off the shelf properties - the
  material is made at the same time as the part.

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Hand Lay-upspray gel coat application
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Hand Lay-upapplication of gel coat by roller
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Hand Lay-upapplication of reinforcement
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Hand Lay-upapplication of reinforcement
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Hand Lay-upapplication of resin and consolidation
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Hand Lay-upfurther consolidation
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Hand Lay-upaddition of woven ply
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Chopper head for spray-up
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Spray-up equipment
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Spray application on existing gel coat
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Spray application of fibre and resin
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Consolidation after spray application
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Advantages of Hand Lay-up

• Low cost tooling
• Low cost materials
• Large parts possible
• Low technology
• Room-temperature cure

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Disadvantages of Hand Lay-up

• Laminate quality dependent on operator skill.
• Poor working environment.
• Health and safety issues associated with styrene

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Advantages of Spray Lay-up

• Low cost tooling.
• Rapid deposition.
• Mature industry

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Disadvantages of Spray Lay-up

• Resin-rich laminates.
• Only short fibres can be used.
• Low viscosity resins required (inferior
  properties).
• Health and safety implications of styrene.
• High wastage.

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Hand lay-up

• Materials options
• Any thermosetting resin.
• Any reinforcement (some heavy fabrics hard to
  wet-out)

• Applications
• Production boats
• Water storage tanks
• Architectural mouldings.

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Spray lay-up

• Materials options
• Generally polyester.
• Glass roving only

• Applications
• Small production boats
• Enclosures
• Vehicle body panels.

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Effect of voids on properties
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Sources of voids

• Layers of air trapped between plies
• Dissolved air or volatiles emerging from solution
• Resin shrinkage on cure
• Poor wetting of fibre surface
• Lack of impregnation

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Effect of consolidation pressure on voids
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Vacuum Bag Moulding

• Uses contact mould.
• Wet lay up or specialist prepreg materials -
  usually epoxy and other high performance, long
  cure time resins.
• Room temperature cure or oven cure under vacuum
  only.
• Autoclave cure under pressure for highest quality
  laminates.

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Process schematic (SP Systems)
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Vacuum bagging
Preparation of carbon/epoxy prepreg
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Vacuum bagging
Hand lay-up of tailored prepreg
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Vacuum bagging

• Application of peel-ply to back of laminate.
  Gives clean textured surface for subsequent
  bonding or painting

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Vacuum bagging
Application of release film (semi-porous)
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Vacuum bagging
Breather mat added to lay up. Sealant tape
applied to mould flanges.
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Vacuum bagging
Nylon bagging film attached to sealant tape.
Pleats ensure excess bag to conform to mould
contours.
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Vacuum bagging
Vacuum connection attached through bagging film.
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Vacuum bagging
Vacuum applied - check for leaks and ensure
consolidation.
Completed lay up ready for cure cycle.
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40 m wind turbine blade. Plywood/epoxy wet lay
up prior to vacuum bagging.
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40 m wind turbine blade. Application of vacuum
bag.
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Effect of consolidation pressure on voids
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Composite panel being loaded into autoclave.
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Vacuum bagging

• Disadvantages
• High cost and storage requirements of prepregs.
• High labour/skill content.
• Cost of consumables.
• Capital cost of oven / autoclave.

• Advantages
• High quality composite parts.
• Large sizes possible.
• Relatively low cost, lightweight tooling.
• Clean manufacturing environment.

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Vacuum bagging applications
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JEC Composites May 2003
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Autoclave technology Length doesnt matter.
Cost increases exponentially with diameter.
Hoop stress ? d end load ? d2
Aeroform Ltd
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12m spar for A400 (resin film infusion) GKN
Westland Aerospace
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• MANUFACTURE OF POLYMER COMPOSITES BY COMPRESSION
  MOULDING

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Compression moulding

• Materials options
• Dry reinforcement / liquid resin
• Polyester and phenolic resin moulding compound
  (SMC, BMC)
• Epoxy prepregs

• Applications
• Car and truck body panels, engine components
• Electrical housings
• Building cladding panels
• High precision optical parts

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Typical compression moulding press
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Cold press mouldingdry fibre / liquid resin
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Cold press mouldingdry fibre / liquid resin
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Cold press mouldingdry fibre / liquid resin
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Sheet moulding compound
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Truck body parts compression moulded from SMC
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Advanced composite parts from compression moulded
carbon prepreg (heated tooling)
yacht steering gear
movie camera
safety helmet
record deck tone arm
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Compression moulding

• Advantages
• Rapid cycle times with polyester SMC
• Excellent surface finish in heated tooling
• High tolerances
• Low material waste

• Disadvantages
• High capital investment
• Limited press size
• High cost tooling

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Resin Transfer Moulding

• Matched mould tool - fixed cavity.
• Dry reinforcement preform loaded into tool.
• Catalysed liquid resin injected under positive
  pressure.

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RTM process schematic (www.plastech.co.uk)
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RTM Tooling
Bottom half
Top half
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RTMLoading the reinforcement preform
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RTM
Resin injection
Closing the tool
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RTM - part removal
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RTM - Ford Transit Van Roof
Plastech Thermoset Tectonics
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RTM Applications
Plastech
University of Plymouth
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RTM - Advantages

• Good thickness tolerance
• Two moulded surfaces
• High fibre content possible
• Reduced styrene emission
• Potential for automation

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RTM - disadvantages

• Expensive tooling
• Size limitations
• Flow prediction difficult
• Properties of low viscosity resins

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Vacuum Resin Infusion

• Also known as
• VARTM
• RIFT
• SCRIMP

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Vacuum Resin Infusion

• Uses contact mould.
• Dry reinforcement encapsulated by sealed
  polymeric bag or lightweight laminate.
• Catalysed resin drawn through reinforcement under
  vacuum.

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Process schematic (SP Systems)
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Vacuum resin infusion
Tool with fibre mat loaded
Contact mould tool
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Vacuum resin infusion
Infusion under vacuum
Semi-rigid top attached
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www.polyworx.com
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www.polyworx.com
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Resin Infusion - advantages over hand lay-up

• Higher quality laminate
• Reduced styrene emissions
• Cored laminates in one operation

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Resin Infusion - disadvantages over hand lay-up

• Careful process control required
• More consumables
• Low viscosity resin required

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Resin Infusion - advantages over RTM

• Much lower tooling cost
• Less processing equipment required
• No size restriction
• Can adapt existing hand lay-up tooling

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Resin Infusion - disadvantages over RTM

• Only one moulded surface
• Less control over part thickness
• Injection time limited by 1 bar pressure

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• Filament Winding

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Filament winding process schematic
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Raw material - continuous fibres
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Filament winding continuous fibre impregnation
winding on to rotating curved surface under
tension
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Advantages of Filament Winding

• Rapid process
• Highly automated
• Controlled resin content
• Minimum fibre cost
• High fibre content - good structural properties

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Disadvantages of Filament Winding

• Shape limitations
• Difficult to place axial reinforcement
• High mandrel and equipment costs
• Unmoulded outer surface

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• Pultrusion

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Pultrusion process schematic
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Pultrusion die detail
Direct resin injection into die
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Advantages of Pultrusion

• Fast and economic process
• Good control of resin content - consistent
  properties
• Closed mould - low emissions
• Minimum fibre cost

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Disadvantages of Pultrusion

• Limited to constant cross-section components
• High cost of heated dies

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• Centrifugal Casting

• Reinforcement and matrix deposited on
  inside of cylindrical mould
• Consolidation by mould rotation

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Resin and chopped fibre deposition
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Split mould for part removal
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