Transcript Slide 1

Processing of PMCs
Varies from simple intensive methods to
automated methods
 The methods of production will depend on
factors such as cost, shape of
components, number of components and
required performance

1. Hand methods
a)
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Hand lay-up
Mould is treated with a release agent-to
prevent sticking
Gel coat layers are placed on the mold- to give
decorative and protective surface
Put the reinforcement (woven rovings or
chopped strand mat)
The thermosetting resin is mixed with a curing
agent, and applied with brush or roller on the
reinforcement
Curing at room temperature
Concept of hand lay-up process

What are the Advantages and
Disadvantages of Hand lay-up
methods?
2)
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Spray-up
Variation of hand lay-up
Mould is treated with a release agent-to prevent
sticking
Gel coat layers are placed on the mold- to give
decorative and protective surface
The gun sprays the mixture of chopped fiber,
resin & catalyst on to a mould
Rolled out to remove entrapped air & give a
smooth surface
Poor roll out can induce structural weakness by
leaving air bubbles, dislocation of fibers and
poor wet out
Concept of spray-up process
2. Moulding Methods
Matched-die moulding (Acuan Terpadan)
-The composite material is pressed between
heated matched dies
-Pressure required depends on the flow
characteristics of the feed materials
- The feed materials flows into the contours
of the mould and cures at high temp.
a)
Matched die-moulding
2 forms of feed materials;
a) Sheet moulding compound (SMC)
Sheet of resin-fiber blend which contains
additives (curing agent, release agent &
pigments). Clean to be used & give good
consistency in properties
b) Dough moulding compound (DMC)
Blends (in dough forms) of all the
necessary constituents (but only short
fibers are used)

2. Moulding Methods
b) Forming methods by employing gas
pressure (Kaedah Tekanan Gas)
3 methods
i) Vacuum forming/vacuum bagging (Beg
vakum)
ii) Autoclave moulding (Acuan autoclave)
iii) Pressure bagging (Beg tekanan)
Vacuum Bagging
-1 die is required for this process
- Pressure is obtained atmospheric
1. Used preimpregnated
reinforcement/ wet layup materials
2. Flexible sheet is
sealed to the mould
3. Vacuum until air
is removed
Bleeder/Breather ply is
used to trap air.
Vacuum bagging kevlar laminate
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Autoclave Moulding
-Autoclave, tube
structure and
Pressures are supplied
in it
- Mould is placed in
autoclave
-Supply gas (N2), and
forced the bag into the
mould
- Able to produce high
density, product for
critical applications such
as in the aerospace
industry
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Pressure Bagging
-A flexible bag is placed
over
the lay-up on the mould
- Atmospheric pressure
is used for shaping
- Compressed air forces
the lay-up into the
mould
c) Low pressure, closed mould system
- This method consists of placing the
reinforcement in a closed mould, then
insert the matrix materials into the mould
- Example in Resin Transfer Molding (RTM),
the low viscosity resin is injected into the
closed mouldusing a low pressure, and
cured
Resin Transfer Molding (RTM)
 Is commonly used in the aerospace and automotive
industry.
 The process consists of mixing resin with a hardener (or
initiator) and injecting the combination into a mold
which contains dry fibers.
 The mix of resin & hardener is then injected at a low
pressure of 5 psi (34.5 kPa) into a mold.
 The resulting part is cured at room temperature for
several hours.
Advantages
 Low pressure 5 psi (34.5 kPa)
 Fiber loadings are typically around 50-60% (Volume)
 Preform architecture can be very complicated
Typical RTM Process
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Process diagram of the automotive
industry
Hand lay-up – used
For complex and large
Component in small
quantity but the
process is slow
Match die
moulding- expensive
but component can
be produced rapidly
RTM- small runs,
simmple components,
and longer run for
more complex
components
3. Pultrusion/Pultrusi
Used to manufacture components with
continuous lengths and constants crosssectional shape (rod, tubes, beam, etc)
 Continuous process, easily automated
(production rates are high, hence it is vey
cost effective), variety of shapes are
possible
 Starting materials can be in the forms of
Prepreg or fiber + resin
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Schematic Diagram of pultrusion
process
Methods;
 Continuous rovings of the reinforcement
are impregnated with the resins (passing
through a bath of resin)
 Then pulled through the heated die
(compact & give shape to the composites)
 Curing takes place in the heated die &
Oven
 Puller used to pull the whole system with
certain speed (Pultrusion- pulling action)
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4. Filament Winding/Pelilitan Filamen
Process to produce a hollow (usually
cylindrical) shape
 End products; pressure vessel, storage
tanks, and aerospace parts such as
helicopter blades.
 Wet winding (fiber + resin) & dry winding
(prepreg)
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Schematic diagram of filament
winding process
Helical
Circumferential
Polar
Methods;
 The fibers are passed through the resin
bath
 Then continuously wound onto the
mandrel
 After number of layers, curing is carried
out in an oven or room temperature.
 Mandrel is removed
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Some Commercial PMCs
1.
Fiber reinforced epoxy
-
Glass fibers are common reinforcement for PMCs
Glass fiber reinforces polyesters (GRPs) are
popular in the market, glass fiber reinforced
epoxies (GREs) are the second
GREs- good strength & stiffness, strong bonding
of glass fibers to epoxy
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GREs are generally employed in low
volume & high technology applications
 Coupling agents are used to improved
wetting and bonding; silanes
 Glass fibers in composites can be
degraded by water, results in loss of
strength
 Water reaches the fibers via defects or by
diffusion in matrix, then attack the
interface
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Effect of different types of Coupling Agents on the
strength of epoxy laminates as a Function of the
Time exposed to Boiling Water
Theeffect of a silane coupling agent on interfacial
behavior in the presence of water
Hydrolysis of the covalent M-O bond
b) Shear displacement at the polymer-glass interface
Some Commercial PMCs
2) PEEK matrix composites
-PEEK – thermoplastic (TP) (advantages of
TP???)
- PEEK is a relatively costly TP, with good
mechanical properties
- Used in high performance applications, i.e.
carbon fiber reinforced PEEK is a
competitor for carbon reinforced epoxy,
Al-Cu & Al-Li in the aircraft industry
Some Commercial PMCs
3) Rubber Matrix Composites
- Reinforced rubber used in conveyer belt,
tyres, fire-resistant cable sheathing, etc.
- Common type of reinforcement in rubber
is Carbon Black (increase stiffness,
strength & abrasion resistance). Carbon
can absorb most of UV from natural light,
hence decrease degredation of rubber
Another example of particulate
reinforcement is Aluminium tri-hydroxide,
which is flame retardent. Can be
incorporated up to 70% into the rubber
insulation of heavy duty electrical cable.
 Hybrid carbon black and continuous
reinforcement (steel wire) are used in tyre
applications
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