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)
-
-
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)
-
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.

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

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

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

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)

QUIZ-Soalan 2004/2005

Bincangkan salah satu teknik penghasilan
komposit polimer yg menggunakan
prapreg sebagai bahan pemula (teknik
kering). Perbincangan harus meliputi
gambarajah skematik teknik yg dipilih,
bagaimana teknik ini beroperasi, kebaikan
teknik kering ini jika dibandingkan dengan
teknik basah dan produk yang dihasilkan
daripada teknik ini.
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)

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

Composite Manufacturing &
Complexity
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
-
-
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

Effect of different types of Coupling Agents on the
strength of epoxy laminates as a Function of the
Time exposed to Boiling Water
The effect 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 retardant. 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
