The fabrication methodology of a composite part depends mainly on three factors: (i) the characteristics of matrices and reinforcements, (ii) the shapes, sizes and engineering details of products, and (iii) end uses. The composite products are too many and cover a very wide domain of applications ranging from an engine valve to an aircraft wing. The fabrication technique varies from one product to the other.

1. COLLOQUIUM PRESENTATION
ON
COMPOSITE FABRICATION TECHNIQUES
1
Supervisor –
Dr. V.R.Komma
Mechanical Engg. Deptt.
MNNIT Allahabad
Submitted by –
Sandeep Kashyap(2015PR21)
M.Tech. (Prod. Engg.)

2. 1. INTRODUCTION
2. FABRICATION PROCESSES FOR POLYMER
MATRIX COMPOSITES(PMC)
3. FABRICATION PROCESSES FOR METAL
MATRIX COMPOSITES(MMC)
4. FABRICATION PROCESSES FOR CERAMIC
MATRIX COMPOSITES(CMC)
5. FUTURE CHALLENGES
6. CONCLUSION
REFERENCES
2
OUTLINE

3.  The fabrication methodology of a composite part depends
mainly on three factors:
(i) the characteristics of matrices and reinforcements,
(ii) the shapes, sizes and engineering details of products, and
(iii) end uses.
 The composite products are too many and cover a very wide
domain of applications ranging from an engine valve to an
aircraft wing.
 The fabrication technique varies from one product to the
other.
3
1. INTRODUCTION

4. Important moulding methods for fabrication of polymer
matrix composite structural parts may be classified
under :-
a) Matched Die Mould – Some of it includes
Compression Moulding, Cold Stamping, Press
Moulding and Injection Moulding.
b) Contact Mould (also called open mould) – Some of it
includes Vacuum Bag Moulding, Pressure Bag
Moulding and Autoclave.
c) Filament Winding and
d) Pultrusion
4
2. FABRICATION PROCESSES FOR PMC

5.  The common feature in this technique is moulds are
usually fabricated with cast iron, steel and aluminium
alloy.
 Fibre reinforced plastics or wooden moulds are also
used in some cold moulding processes.
 The mating surfaces of the moulds are first polished,
cleaned and coated with a release agent. Next a gel coat
is applied.
 The gel coat is not provided, when the moulded part is to
be adhesively bonded to another part, as the coat may not
allow proper bonding.
 Venting ports are provided in the moulds for escape of
excess resin and volatile matters.
5
a. Matched-Die Mould Methods

6. (i) Compression Moulding :
 Moulding material may be predetermined quantity of BMC, SMC or
prepregs.
 The moulds can have a single cavity or multiple cavities with complex
curved shapes.
 The pressure is applied by mounting the moulds in a mechanical or
hydraulic press or by some external means.
 On application of pressure and temperature, the mould material softens
and then flows and fills the mould cavity. Further, continuation of heat and
pressure accelerates curing.
6(PMC, Defense Handbook (2002))

7.  It is employed in fabrication of automobile body panels, housings for
electrical appliances and machines, covers, and several other parts.
(ii) Cold stamping Moulding :
 In this, the thermoplastic sheets are preheated, laid on the mould along
with reinforcements and then cold pressed.
 An extension of this method is continuous production of fibre reinforced
thermoplastic laminates is illustrated in Fig. below.
 Alternate layers of fibre fabrics and thermoplastic films are fed through
hot rollers that melt the resin and force it to penetrate and coat the
individual fibres. The consolidated laminate is then passed through cold
rollers which cure and harden the laminate.
7PMC, Defense Handbook (2002)

8. (iii) Press Moulding :
 It is used to make flat, slightly curved and corrugated laminates.
 On the application of pressure the excess resin is squeezed out and passes
through the pores of nylon cloth(i.e. peel ply to achieve required surface
finish) and perforations of Teflon film and gets absorbed by the bleeder
(e.g., jute cloth).
 The pressure is applied normally to allow uniform resin distribution. The
uniform flow of excess resin out of the moulding can be achieved by
applying vacuum to one of the surfaces of the mould cavity.
8
(PMC, Defense Handbook (2002))

9. (iv) Injection Moulding :
 It is suitable for thermoplastic resin systems.
 If the reinforcements are in the form of particles or very short fibres. The
mix is first heated in an injection chamber and then forced into the closed
mould cavity under high pressure and is allowed to cure. It is suitable for
fabrication of small to medium size parts such as valves, gears,
instrument panels, etc.
9
 If the reinforcements are in the
form of preforms, they are laid
in the mould cavity and the fluid
resin is then injected into the
mould cavity. The process is
known as resin injection
moulding.
 For larger mouldings such as
boat hulls, resin is injected at
several locations. (NV Srinivasulu (2012))

10. 10
 Some Applications of Match-Die Mould Method

11.  In this there is only one mould (Male or female), the surface of which is first
polished, cleaned and coated with a release agent & gel.
 The moulding materials are laid on the mould by either the hand lay-up process or
the spray-up process.
11
2.2 Contact Mould (also called open mould)
 In the hand lay-up process, woven rovings, or chopped strand mats are placed
layerwise, with each layer coated with resin using a brush or a spray gun.
Some time gap is allowed for the
applied resin coat to gel, before
laying the next layer and applying
resin to it. Squeeges or rollers are
used for uniform distribution of resin
and consolidation for the laminate.
 In the spray-up process, chopped
strands or particulate reinforcements
and the resin are sprayed
separately/simultaneously to the
mould surface. After which, the
moulding is allowed to cure.
(PMC, Defense Handbook (2002))

12.  For compact and voidless finished products, other improved techniques are
vacuum bag moulding, pressure bag moulding processes and autoclave
moulding.
(i) Vacuum Bag Moulding :
 The whole moulding system is covered with a flexible vacuum bag. The
edge of the bag is sealed using vacuum sealing compounds.
12
 Layers of bleeder,
perforated Teflon film,
and nylon peel ply, in
order.
 When vacuum is applied, volatiles, trapped air and excess resin escapes
out and further consolidates the laminate. The whole assembly can be
put in an oven, if a high temperature curing is needed.
(PMC, Defense Handbook (2002))

13. (ii) Pressure Bag Moulding :
 In this case, the vacuum bag is replaced by a pressure bag and the whole
system is covered by a pressure plate.
 The required pressure is then applied through an inlet pipe located at the
cover plate.
 The higher pressure ensures proper consolidation and densification of the
composite lay-up. However, the method cannot be applied to a male
mould.
13
(PMC, Defense Handbook (2002))

14. (iii) Autoclave Moulding :
 It is a highly sophisticated process in which controlled temperature and
pressure can be applied. In addition, vacuum is also applied to suck
volatile matters and entrapped air or gases.
 The whole assembly is put inside an autoclave. Curing takes place in
presence of simultaneous. pressure and temperature.
14
 After curing, the mould is
taken out of the autoclave.
 It yields highly densified
products and is therefore
favoured in fabrication of
major aerospace components
like aircraft wing parts,
helicopter blades, etc.
(PMC, Defense Handbook (2002))

15. 15
 Some Applications of Contact Mould Method

16. 16
2.3 Filament Winding
 The filament winding process is employed for fabrication of a continuous
fibre reinforced composite structure having an axis of revolution.
 Continuous fibre strands or rovings are first coated with resin in a resin
bath and then fed through rollers to squeeze out excess resin and finally
wound, under constant tension, around a collapsible mandrel.
 The mandrel is usually made of steel. However, other materials like
plastic foam and rubber are also used in fabrication of some mandrels.
(PMC, Defense Handbook (2002))
(PMC, Defense Handbook (2002))

17.  There are basically 2 types of filament winding patterns: helical winding
and biaxial winding.
 After winding is complete, the mandrel is removed from the carriage and
placed in an oven, if required, for curing. Filament wound products for
aerospace applications are normally cured in an autoclave.
 Common examples are tubes, pipes, cylindrical tanks, pressure vessels,
rocket motor cases, etc.
17

18. 18
2.4 Pultrusion
 In this continuous fibre strands taken from a number of spools are
sequentially pulled through a resin bath, a shaping guide and a hot die.
 The fibres are coated in the resin bath and the excess resin is squeezed out.
 The shaping guide provides a gradual change from a simpler to a more
complex pre-formed shape close to that of the pultruded part.
 The final shape is realized when the preformed shape is pulled through a
hot die and gets cured.
(PMC, Defense Handbook (2002))

19.  Continuous strand mats and woven fabrics can also be pulled along with
filament strands to provide better transverse properties to the pultruded
sections.
 The die is a very critical component in the fabrication process. It is usually
made of chromium plated steel and should have a highly smooth surface.
19
 Thermosets like epoxies and
polyesters are normally used in
the pultrusion process.
 A pultrusion machine
SPACETRUDER (developed at
Vikram Sarabhai Space Centre,
Trivandrum, India). It can
produce continuous lengths of
FRP sections such as rounds,
square bars, channels, angles,
etc.

20. 20
 Aluminium, magnesium, titanium and nickel alloys are
commonly used as metal matrices, although several other
matrix materials including super alloys have also been used.
 Both metal and ceramic reinforcements are employed.
 Important moulding methods for fabrication of MMC parts
may be classified under :-
(i) Diffusion Bonding
(ii) Powder Metallurgy Process
(iii) Casting
3. FABRICATION PROCESSES FOR MMC

21.  Composite laminates are produced by consolidating alternate layers of
precursor wires or fibre mats and metal matrix sheets or foils under
temperature and pressure.
 A monotape (i.e., a unidirectional lamina) in which a fibre mat is
sandwiched between two metal sheets or foils, forms the basic building
block.
 Several complex composite components can be fabricated by stacking
monotapes as per design requirements.
 Under temperature and pressure metal sheets or foils diffuse through
fibre layers to form a laminate. A multilayered laminate may have any
desired stacking sequence.
 Carbon fibres have been successfully combined with matrices like
aluminium, magnesium, copper, tin, lead and silver to make a wide
range of carbon fibre reinforced metal composites.
21
(i) Diffusion Bonding

22.  One interesting example is the 3.6m long high gain antenna boom that
acted as a wave guide for the Hubble space telescope. The boom is made
with diffusion bonded carbon fibre reinforced aluminium composite.
22
(MMC, Defense Handbook (2002))

23.  Almost all metals and their alloys can be converted into powder form by
atomization techniques.
 In one process (known as powder cloth process), metal matrix powders
are mixed with an organic binder and then blending with a high purity
Stoddard solution.
 On application of low heat, Stoddard solution evaporates leaving behind
dough-like mixture which, on rolling, yields a metal powder cloth.
 Alternate layers of powder clothes and fibre mats, when hot press bonded,
form a composite laminate. Binders usually burn out without leaving any
residue.
 When reinforcements are in form of short fibres and particulates, metal
matrix powder and reinforcements are thoroughly blended and degassed to
remove volatiles and then composite ingot is formed by hot pressing in
vacuum.
 Composite ingot is then used to fabricate structural components using
secondary fabrication processes. 23
(ii) Powder Metallurgy Process

24.  In thermal spray processes, metal powders, are deposited on fibre
substrates using either plasma spray or arc spray techniques.
 Plasma spray technique is employed to deposit spherical metal powders
that are injected in the plasma stream (the temperature is about 10,000K
and the traveling speed is around Mach 3) within the throat of the gun.
Powder particle should melt, but not vaporize before reaches substrate.
 Arc spray technique uses continuous metal matrix wires of 0.16-0.32 cm
dia. 2 wires of opposite charge are fed through an arc spray gun. Electric
arc produced causes tips to melt. Argon gas stream carries and deposit
them on substrates.
24
(Kaczmara J.W. (2000)) (Kaczmara J.W. (2000))

25.  Monotapes produced by thermal spray processes are fabricated by
diffusion bonding processes for structural components
 The powder metallurgy process has been used to produce composites such
as boron and carbon fibres with aluminium alloy, SiC fibres with
chromium alloys, boron and Al2O3 fibres with titanium alloy, and
several other composite systems.
25
 Some Applications of Powder Metallurgy Process :

26.  Casting or liquid infiltration is process in which molten matrix is
infiltrated into a stack of continuous fibre or discontinuous reinforcements
and is then allowed to solidify between the inter-reinforcement spaces.
 Some important casting methods are stir castings, pressure/squeeze
castings, and centrifugal casting.
 In stir casting, required amount of metal matrix is weighted and placed in
graphite crucible and heated to melt using furnace. All the pre- weighted
reinforcing elements are mixed with molten metal and a constant vigorous
stirring was done for 15 to 20 minutes until a clear vortex formed.
26
(iii) Casting

27.  At the pouring temperature, the molten mixture was poured into the
permanent mould and allowed to solidify for few minutes. After complete
solidification it is withdrawn and machined accordingly.
 In Centrifugal casting, solidification takes place in a rotating mould. In
this process, the centrifugal acceleration forces the heavier discontinuous
reinforcements to concentrate near the outer periphery and the lighter ones
lie closer to the axis of rotation.
 Pressure/Squeeze casting is the process in which the molten matrix is
infiltrated, under high pressure, onto a preheated stack of discontinuous
reinforcements or fibre preforms laid on a metal die. Solidification takes
place also under pressure. The Toyota piston, made of ceramic fibre and
aluminium matrix, is one such example.
27

28. 28
 Some Applications of Casting Process :

29. 29
 Ceramic such as glass, glass-ceramics, borides, carbides,
graphite, nitrides and silicates reinforced with ceramic
particles, whiskers and fibers provide enhanced strength and
toughness even at high temperatures.
 Important moulding methods for fabrication of CMC parts
may be classified under :-
(1) Hot Press Sintering
(2) Liquid Infiltration
(3) Reaction Sintering
(4) Chemical Vapour Deposition Process
4. FABRICATION PROCESSES FOR CMC

30.  SiC whiskers are very commonly used to reinforce matrices such as glass,
ZrO2, B4C, Al2O3, Si3N4 and several other ceramics.
 Number of glass systems such as lithium aluminosilicate (LAS),
magnesium aluminosilicate (MAS) etc. have been hot pressed at
relatively lower temperature without causing any damage to the
reinforcement. 30
4.1 Hot Press Sintering
(Mehdi Shahedi Asl (2015))

31.  Infiltration of molten ceramics is similar to the resin injection molding
process.
 The high melting points of ceramics, may degrade the reinforcements.
 This problem can be overcome by the use of polymer precursors that bring
down the process temperature.
31
4.2 Liquid Infiltration
 However, during the conversion of
a polymer precursor to the ceramic
matrix, a lot of volatile matters
escape causing shrinkage of the
matrix. The matrix also becomes
porous.
 The porosity can be reduced to a
large extent by reimpregnation.
Several precursor polymers have
been studied to produce SiC and
Si3N4matrices.

32.  Reaction sintering eliminates problems associated with hot press sintering
and liquid infiltration, such as fibre damage, matrix shrinkage, etc.
 In this process, ceramic matrices are reaction formed.
 For eg., silicon nitride(RBSN) is made from finely divided silicon powders
and subsequently reacted in a mixed nitrogen/hydrogen atmosphere at
1,200 to 1,250 °C. The nitrogen permeates the porous body and reacts with
the silicon to form silicon nitride within the pores. The piece is then heated
to 1,400 °. The entire reaction-sintering process can last up to two weeks.
Although up to 60 percent weight gain occurs during nitriding,
dimensional change is less than 0.1 percent.
 The SiC matrix has also been successfully reaction bonded with SiC and
carbon mixture powder exposed to a liquid/vapour Si.
 This is a “net shape” process.
 Main drawback is that resulting composite may have excessive porosity.
32
4.3 Reaction Sintering

33.  The preform is kept in a high temperature furnace (reactor).
 A carrier gas (H2, Ar, He, etc.) stream passes through a vessel containing
gaseous reagents and carries their vapour into the reactor.
 Chemical reaction of reagents leads to the formation and deposition of
ceramic matrix vapour on the heated surface of the preform.
 Other reaction powders diffuse out of the preform and are carried by the
flowing gas stream out of the furnace.
 The deposition process continues, until all the inter fibre spaces are filled
up resulting in a homogeneous and more or less void free composite.
 Main advantage is that it causes minimum damage to the fibres(due to low
pressure & temperature) and also this process permits fabrication of
composite parts with irregular shapes.
 A typical reaction such as
CH3 + SiCl3 → SiC + 3HCL
is responsible for deposition of SiC vapour.
33
4.4 Chemical Vapour Deposition Process

34.  This process been found to yield superior carbon-carbon composites and
has been used to produce aerospace components such as aircraft brake
discs and engine exit nozzles, rotors, etc.
34
 Some Applications of CMCs :

35.  A major challenge relating to composite design is the unavailability
of simulation tools and a general lack of composite material
characterization.
 Manufacturing is an issue for composites in the automotive sector
when one considers the high production volumes required. One
reason is the cost of the raw materials, and the lack of suitable
manufacturing processes.
 There is an ever-increasing demand for the manufacturing of large
and complex shaped parts, which are either quite expensive or very
difficult to fabricate.
 More improved fibres are needed that are stable for long times at
high temperature.
35
5. Future Challenges

36.  Due to their higher strength-to-weight ratios, composite materials
have an advantage over conventional metallic materials; although,
currently it is expensive to fabricate composites.
 Components must be designed with composites in mind from the
onset of the design process. For this reason, the designer must have
a good understanding of the candidate materials and must be well
versed in the manufacturing techniques that may be employed.
 Day by day, there is an increased number of developments in the
area of fabrication science in tune with the requirement of
dimensions, strength, applications of composite.
36
6. Conclusion

37. 1. Basutkar A.G. and Kolekar A., ” A Review on Properties and Applications of
Ceramic Matrix Composites”, IJRSI, Vol. II, Issue XII, 2015, pp:28-30
2. Awalellu K.A., “A Review on Properties and Applications of Polymer
Matrix Composites”, IJRSI, Vol. III, Issue IA, 2016, pp:53-55
3. Begg A.R., ”Application of Metal Matrix Composite”, BP Metal Composites Ltd., 1991,
pp:42-45
4. Akay M., “An Introduction to Polymer Matrix Composites”, Bookboon.com, Vol. 1, 2015.
5. “Metal Matrix Composite Handbook”, Department of Defence USA, Volume 4 of 5, 2002.
6. “Polymer Matrix Composite Handbook”, Department of Defence USA, Volume 4 of 5,
2002.
7. “Ceramic Matrix Composite Handbook”, Department of Defence USA, Volume 4 of 5,
2002.
8. Krishnakanth K. and Sivakuma E.R., “Design and Fabrication of Composite Gears “,
IJIRSET, 2015, pp:364-372
9. Rawal S., “Metal Matrix Composites for Space Application”, MMC for space:Overview,
2001, pp:14-17.
10. Divya H.V., Naik L.L., and Yogesha B.,”Processing Techniques of Polymer Matrix
Composites – A Review” International Journal of Engineering Research and General
Science, Volume 4, Issue 3, 2016, pp: 357-362.
37
REFERENCES

38. 11. Halbig M.C., Jaskowiak M.H., Kiser J.D. and Zhu D., “Evaluation of Ceramic Matrix
Composite Technology for Aircraft Turbine Engine Applications”, NASA Glenn Research
Centre, 2013, pp:1-11.
12. Kaczmara J.W., Pietrzakb K., and Włosinskic W., “The production and application of metal
matrix composite materials “, Journal of Materials Processing Technology, 2000, pp: 58-67
13. Donato et al., “Process for producing ceramic matrix composite by liquid infiltration”, U.S.
Patents, 1998, Patent No. 5,853,653
14. Macke A., Schultz B.F., and Rohatgi P., “MMC for Automotive Industry”, Center for
Composite Materials,University of Wisconsin–Milwauke”, 2012,pp:19-23.
38
REFERENCES (Contd.)