Composite Manufacturing Flashcards
What are the primary processing routes for high viscosity thermoplastics?
injection moulding
extrusion
hot pressing
What are the main processing routes for low viscosity thermosets?
Wet lay up
pultrusion
filament winding
resin transfer moulding
pre preg lay up
compression moulding
why aren’t high forces used when processing low viscosity thermosets?
can bleed resin out of fibres
high forces can be used after solidification
what are the general processes used for both thermolplastic and thermosets?
powder processing
hot pressing
injection moulding
what are the general steps for manufacturing thermosets?
- Preparing the fibres and matrix
- combining the fibres and matrix
- void removal
- consolidation
- resin curing
how are the fibres and matrix prepared for thermosets?
unidirectional cloth, woven fabrics and mats cut to shape and size
mix curing agents and resin
preforms can be used for resin transfer moulding and usually made by winding/weaving/braiding
how are the fibres and matrix combined for thermosets?
wet lay up
pultrusion
filament winding
resin transfer moulding(RTM)
how does void removal work for thermosets?
must be done before cured
vacuum bagging - adds pressure removes any voids
how does consolidation work for thermosets?
pressure applied
autoclave - vacuum 1 atm
how does resin curing work?
temperature dependant on resin
higher temp generally better mechanical properties
How does hand lay up work?
- apply release agent to one sided mould
- apply gel coat
- place prepared fabric/mat into mould
- add prepared resin and work in
- repeat 3+4 for thickeness
- cure
What are the applications of hand lay-up?
lorry trailers
boats
storage tanks
baths
low performance aircraft
architectural mouldings
What are the advantages of hand lay-up
Cheap
Versatile (any goemetry)
Simple to add features(holes)
Good for prototypes
Simple mould materials (wood)
What are the disadvantages of hand lay-up?
poor properties
labour intensive
relatively slow
quality consistency
properties skill dependent
only one moulded surface
resin fumes
How does spray lay-up work?
- apply release agent to one sided mould
- apply gel coat
- spray chopped fibre and prepared resin into mould
- work in using roller (consolidation)
- repeat 3+4 for thickness
- cure
What are the applications for spray lay up?
same as hand lay up
What are the advantages of spray lay-up?
Cheap
Versatile (any geometry)
simple to add holes etc
good for prototypes
simple moulds (wood)
faster than hand lay up
What are the disadvantages of spray lay-up?
poorer properties than hand lay up
fibres randomly orientated and short
Labour intensive ( more automated than hand lay up)
1 moulded surface
messy, fumes
How does pultrusion work?
- assemble reinforcements
- draw fibres through a resin bath (dip or drum)
- draw through die and cure
- cut to length
What are the applications of pultrusion?
construction beams
piles for buildings
bridges
ladders
What are the advantages of pultrusion?
any length
good surfaces
excellent fibre alignment
relatively automated once stable
quality consistency is good
What are the disadvantages of pultrusion?
restricted geometry (straight constant cross section)
medium capital investment
mould materials expensive(steel)
relatively slow
How does filament winding work?
- assemble reinforcements
- draw fibres through traversing resin bath
- wind onto mandrel
- braking system used to control fibre tension
- fibres laid side by side or overlapping
- cure
- remove from mandrel
What are the applications of filament winding?
chemical storage tanks
pipelines
gas cylinders
