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Processing of PMCs

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Vacuum forming/vacuum bagging (Beg vakum) Autoclave moulding (Acuan autoclave) ... Supply gas (N2), and forced the bag into the mould ... – PowerPoint PPT presentation

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Title: Processing of PMCs


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

2
1. Hand methods
  • 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

3
Concept of hand lay-up process
4
  • What are the Advantages and Disadvantages of Hand
    lay-up methods?

5
  • 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

6
Concept of spray-up process
7
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.

8
Matched die-moulding
9
  • 2 forms of feed materials
  • 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)

10
2. Moulding Methods
  • b) Forming methods by employing gas pressure
    (Kaedah Tekanan Gas)
  • 3 methods
  • Vacuum forming/vacuum bagging (Beg vakum)
  • Autoclave moulding (Acuan autoclave)
  • Pressure bagging (Beg tekanan)

11
Vacuum Bagging -1 die is required for this
process - Pressure is obtained atmospheric
1. Used preimpregnated reinforcement/ wet lay- up
materials 2. Flexible sheet is sealed to the
mould 3. Vacuum until air is removed
Bleeder/Breather ply is used to trap air.
12
Vacuum bagging kevlar laminate
13
  • 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

14
  • 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

15
  • 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

16
  • 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

17
Typical RTM Process


18
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
19
3. Pultrusion/Pultrusi
  • Used to manufacture components with continuous
    lengths and constants cross-sectional 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

20
Schematic Diagram of pultrusion process
21
  • 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)

22
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23
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)

24
Schematic diagram of filament winding process
Helical
Circumferential
Polar
25
  • 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

26
Some Commercial PMCs
  • 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

27
  • 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

28
Effect of different types of Coupling Agents on
the strength of epoxy laminates as a Function of
the Time exposed to Boiling Water
29
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
30
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

31
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

32
  • 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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