2. CONTENTS –MANUFACTURING OF COMPOSITES
Preparation of moulding compounds
Prepregs
Hand lay up method
Autoclave method
Filament winding method
Compression moulding
Reaction Injection moulding
3. PREPARATION OF MOULDING COMPOUNDS
High polymer material is mixed with 4 to 10
ingredients each of which discharges a useful
function during moulding or impart some useful
property to the finished artifact
5. TYPES OF MOULDING COMPOUNDING INGREDIENTS-
1.RESIN
It is a binder which holds different constituents together
Resin in the most specific use of the term is a
hydrocarbon secretion of many plants, particularly
coniferous trees.
Resins are valued for their chemical properties and
associated uses, such as the production of varnishes,
adhesives and food glazing agents
6. 1.RESIN
Synthetic resins are viscous liquids that are
capable of hardening permanently.
Otherwise, chemically they are very different from
the various resinous compounds secreted by
plants
8. 1.RESIN
Some are thermosetting plastics in which the term
"resin" is loosely applied to the reactant or product,
or both. "Resin" may be applied to one of two
monomers in a copolymer (the other being called a
"hardener", as in epoxy resins).
For those thermosetting plastics which require only
one monomer, the monomer compound is the
"resin.
10. TYPES OF MOULDING COMPOUNDING INGREDIENTS
2.PLASTICIZERS
Plasticizers are materials that are added to resins
to increase their plasticity and flexibility
They neutralise the part of the intermolecular forces
of attraction between macromolecules of resins
They impart a greater freedom of movement
between the polymeric macro molecules of resin
there by increasing the flexibility and plasticity of
the compound material.
11. 2.PLASTICIZERS
Phthalate esters are
plasticizers used in polyvinyl chloride
(PVC) to soften the hard PVC by
“lubricating” the areas between
polymer strands so that it can be
used in consumer products like
inflatable pools and food packaging.
Almost 90% of the market for plasticizer is for PVC, giving this
material improved flexibility and durability.
Plasticizers work by embedding themselves between the chains of
polymers, spacing them apart (increasing the "free volume"), and
thus significantly lowering the glass transition temperature for the
plastic and making it softer.
12. 2.PLASTICIZERS
Plasticizers evaporate and tend to concentrate in
an enclosed space; the "new car smell" is caused
mostly by plasticizers evaporating from the car
interior.
13. 3.FILLERS
Fillers are added to give the final plastic better
hardness , tensile strength , finish and workability.
Advantages :
Reduces cost
Reduces shrinkage
Reduces brittleness
Examples :
Carborundum,Quartz,Mica to provide extra hardness
Barium salts to make plastic impervious to X-rays
Addition of asbestos provides heat and corrosion
resistance .
14. 4.LUBRICANTS
Added to make moulding of plastic easier.
To impart a flawless , glossy finish to the products .
Prevents plastic material from sticking to the
fabricating equipment.
Eg: Waxes , Oils , soaps etc
15. 5.CATALYSTS OR ACCELERATORS
Are added only in case of thermosetting plastics.
Accelerates the polymerization of fusible resin
during moulding operation into crosslinked infusible
form .
Eg: Hydrogen peroxide
Acetyle sulphuric acid
Benzoyl peroxide
16. 6. STABILIZERS
Improve thermal stability during processing
Eg :
Vinyl chloride
UV light stabilizers are used frequently in plastics,
including cosmetics and films.
The primary function is to protect the substance
from the long-term degradation effects from light,
most frequently ultraviolet light.
20. PREPREGS
Prepreg is the industry term for high quality
reinforced fibers , which are preimpregnated with a
resin system and partially cured to B-stage.
B-stage is an intermediate cure stage of a thermosetting
resin that lies between the completely uncured stage
and a completely cured stage.
Ready to mold or cure material in sheet form which
may be tow , tape , cloth or mat impregnated with
resin.
21. ADVANTAGES
Consistent quality and consistent resin to
reinforcement ratio
Few rejections
Less variance in mechanical properties .
Finest quality material.
Reduce the handling damage to dry fibers.
Increased curing pressure reduces voids and
improves fiber wetting
22. PREPREGS
A prepreg consists of a reinforcement material
preimpregnated with a resin matrix in controlled
quantities.
The resin is partially cured to a B-stage, and in this
form is supplied to the fabricator, who lays up the
finished part and completes the cure with heat and
pressure.
The required heat and pressure will vary with the
resin system and the intended application.
24. METHODS OF PRODUCING PREPREG
1.Solvent Solution Pre-impregnation Process or
Solution Coating
2.Hot Melt Pre Impregnation Procedure.
Solution coating saturates the reinforcement with resin
dissolved in carrier solvent.
Hot melt coating uses heat and pressure to impregnate
the fibers with resin.
The prepreg is typically laid against the paper or
polyethylene film separator called interleaf so that the
preperg don’t stick on to itself and is wound around a
core.
25. 1.SOLVENT SOLUTION PRE-IMPREGNATION
PROCESS
Woven fabric or fiber yarn is passed through a resin
rich solution .
Prepreg is then dried to remove the solvent
Excess resin is then removed via doctor blade or
metering rolls
Then the product is staged to the cold stable
prepreg form (B-Stage )
27. HOT MELT PREIMPREGNATION PROCEDURE
It replaces solvent method because of
environmental concerns and a need to exert better
control over the amount of resin on the fiber .
Issues with Solvent method :
Stringent Air emission control regulations and liabilities .
High cost of maintaining solution ovens .
28. HOT MELT PREIMPREGNATION PROCEDURE
In this process woven fabric or fiber yarn is passed
over a series of rollers .
The molten polymeric resin wets the fibers and then
the resin impregnated sheet of fibers is compacted
over a sheet of release paper and subsequently
wrapped on rolls for storage .
31. HOT MELT PREIMPREGNATION PROCEDURE
At the hot melting machine , the fibers go through a
metered comb to maintain their parallel integrity for even
spreading , and are laid on a release film containing a
controlled amount of resin .
Another role of release film , either dry or film coated , is
positioned above the fibers.
The fibers sandwiched between the films are pulled along
the tape line with pull rollers as pressure is applied from
sets of heated compaction rolls metered to the prepreg
thickness
32. HOT MELT PREIMPREGNATION PROCEDURE
The compaction ensures that the fibers are evenly spread
apart and wet out .
Once through the heated compaction area , the sandwich
typically passes through cooling rolls before the carrier
paper is removed.
Great care is taken to control the temperature
Trimming is done at both sides of the prepreg to exact
width is down just before rewinding
At the end of the tapeline , windup rolls remove one layer
of carrier film and reroll it for disposal.
34. BLEED SYSTEM
The bleed system Prepregs are those, which
contain excess matrix that is bled off during the
cure cycle by the use of BLEEDER PILES.
Bleeder piles are the layers of fiber glass cloth or other
highly absorbent material
35. NO BLEED SYSTEM
Curing of prepreg takes place under heat and
pressure
Bleeder piles are generally not required for no
bleeding system
36. DISADVANTAGES OF PREPREGS
Shelf Life
Since the epoxy is in a B-stage, it is required to be
stored either refrigerated or frozen prior to use.
Additionally, the overall shelf life can be low.
37. DISADVANTAGES OF PREPREGS
Cost Prohibitive
When manufacturing composites through a process
such as vacuum infusion, the raw fiber and resin are
combined on site.
However, when using prepregs, the raw material must
first be prepregged. This is most often done off-site at a
specialized company that focuses on prepregs. This
added step in the manufacturing chain can add
increased cost, and in some instances close to double
the material cost.
39. WET/HAND LAY UP METHOD
Hand Lay-Up is well suited for low volume
production of product.
This method can be used for both corrosion barrier
and the structural portion.
41. WET/HAND LAY UP METHOD
A mold must be used for hand lay-up parts unless
the composite is to be joined directly to another
structure.
The mold can be as simple as a flat sheet or have
infinite curves and edges.
For some shapes, molds must be joined in
sections so they can be taken apart for part
removal after curing.
42. WET/HAND LAY UP METHOD
Reinforcement fibers can be cut and laid in the
mold.
It is up to the designer to organize the type, amount and
direction of the fibers being used.
Resin must then be catalyzed and added to the
fibers.
A brush or roller can be used to impregnate the
fibers with the resin.
The lay-up technician is responsible for controlling the
amount of resin and the quality of saturation.
43. MATERIALS USED FOR HAND LAYUP
Resins:
Any, e.g. epoxy, polyester, vinylester,
phenolic.
Fibres:
Any, although heavy aramid fabrics can
be hard to wet-out by hand.
44. HAND LAY UP METHOD ADVANTAGES
Advantages:
i) Widely used for many years.
ii) Simple principles to teach.
iii) Low cost tooling, if room-temperature cure resins
are used.
iv) Wide choice of suppliers and material types.
v) Higher fibre contents, and longer fibers than with
spray lay-up.
45. Hand Lay-Up Method
Figure 15.4 Hand lay-up : (1) mold is treated with mold release agent; (2) thin gel coat
(resin) is applied, to the outside surface of molding; (3) when gel coat has partially
set, layers of resin and fiber are applied, the fiber is in the form of mat or cloth;
each layer is rolled to impregnate the fiber with resin and remove air; (4) part is
cured; (5) fully hardened part is removed from mold.
47. HAND LAYUP METHOD - DISADVANTAGES
Resin mixing, laminate resin contents, and laminate
quality are very Dependent On The Skills of laminators.
Low resin content laminates cannot usually be achieved
without the incorporation of excessive quantities of
voids.
ii) Health and safety considerations of resins. The lower
molecular weights of hand lay-up resins generally
means that they have the potential to be more harmful
than higher molecular weight products. The lower
viscosity of the resins also means that they have an
increased tendency to penetrate clothing etc.
48. HAND LAYUP METHOD - DISADVANTAGES
iii) Resins need to be low in viscosity to be
workable by hand. This generally compromises
their mechanical/thermal properties due to the need
for high diluents levels.
50. PRODUCTS MADE BY HAND LAY-UP
Generally large in size but low in production
quantity - not economical for high production
Applications:
Boat hulls
Swimming pools
Large container tanks
Movie and stage props
Other formed sheets
The largest molding ever made was ship hulls for
the British Royal Navy: 85 m (280 ft) long
52. Filament winding process
Filament winding is automated processes for
creating parts of simple geometry wherein
continuous resin impregnated fibres are wound
over a rotating male tool called mandrel.
53. FILAMENT WINDING
Resin impregnated continuous fibers are wrapped around a
rotating mandrel that has the internal shape of the desired
FRP product; the resin is then cured and the mandrel
removed.
The fiber rovings are pulled through a resin bath
immediately before being wound in a helical pattern onto
the mandrel.
The operation is repeated to form additional layers, each
having a criss-cross pattern with the previous, until the
desired part thickness has been obtained.
56. TYPES OF FILAMENT WINDING PROCESS
(i) The Polar Or Planer Method
(ii) The High Helical Pattern Winding.
57. THE POLAR OR PLANER METHOD
A winding in which the filament path passes tangent
to the polar opening at one end of the chamber and
tangent to the opposite side of the polar opening at
the other end.
The polar or planer method of winding utilizes a
fixed mandrel and a shuttle that revolves around
the longitudinal axis of the part to form longitudinal
winding patterns.
This type of winding is used if the longitudinal fibres
are required with angle less than 25° to the mandrel
axis.
59. HELICAL WINDING PROCESS
A winding in which the filament or band advances
along a helical path, not necessarily at a constant
angle except in the case of a cylindrical article.In
the high helical pattern winding, the mandrel rotates
while the shuttle transverses back and forth. Both
the mandrel rotation and shuttle movement are in
the horizontal plane. By controlling the mandrel
rotation and shuttle speed, the fibre angle can be
controlled.
.
62. HELICAL WINDING PROCESS
After completion of the winding, the filament wound
structure is cured at room temperature or in an
oven.
The mandrel is removed after the curing. The
mandrel, which determines accurate internal
geometry for the component, is generally the only
major tool.
63. FILAMENT WINDING PROCESS
Low cost mandrel materials such as cardboard or
wood can be used for winding low cost routine
parts. For critical parts requiring close tolerances,
expensive mandrels designed for long term use
may be required.
For high temperature cure 315°C (600°F), graphite
mandrels with low thermal expansion may be
advantageous. However, attention should be paid
for potential difficulties for mandrel removal.
64. TYPES OF MANDRELS
Mandrels are either REMOVABLE or NON-
REMOVABLE.
Removable mandrels are classified according to
the removal techniques as:
• Entirely removed.
• Collapsible.
• Breakable or soluble.
65. THE SELECTION OF MANDREL
1. Part size and complexity
2. Size of openings
3. Resin system and its curing
4. The number of components to be
fabricated.
66. THE REQUIREMENTS FOR A MANDREL
It must be stiff and strong enough to support
its own weight and the weight of the applied
composite while resisting the fibre tension
pressure from winding and curing.
It must be dimensionally stable and should
have thermal coefficient of expansion greater
than the transverse coefficient of the
composite structure.
67. MATERIALS USED FOR CONSTRUCTION OF
MANDREL.
Low melting temperature alloys used for small
diameter applications.
Sand, soluble plaster and eutectic salts used for
irregular shapes.
Inflatable material used in applications where
sometimes the mandrel remains a part of the structure.
Segmented metal used for high production rates, and
where the mandrel can be withdrawn through a small
hole in the part.
68.
69.
70.
71.
72. This process utilises large tonnage presses wherein
the part is cured between two matched steel dies
under pressure and high temperature. The moving
platen is heated either by steam or electricity to
promote thermal curing.
73. Curing of the part is affected by the following
factors:
Size of platen, which determines the length and width of
the part, which can be cured.
Total tonnage of the press, which determines the
pressure to be exerted on the projected surface area of
the part.
74. After placing the laminate to be cured called the
'charge' in the core of the mold, the cavity is then
closed at a rate of usually 4-12 mm/sec.
In most cases the mold is heated to 150°C (302°F),
which causes the charge viscosity to be reduced.
With increasing mold pressure as the mold is
closed, the charge flows towards the cavity
extremities, forcing air out of the cavity.
75. The molding pressure based on projected part area
ranges from 0.7 to 9 MPa (100 to 1200 psi).
Higher molding pressure causes sink marks, while
lower pressure cause scumming of the mold and
porosity.
76. The curing time is usually between 25
sec to 3 minutes depending on several
factors including
resin-initiator-inhibitor reactivity
part thickness
component complexity
mold temperature.
77. ADVANTAGE OF THE COMPRESSION MOLDING
The primary advantage of the compression molding
is its ability of producing large number of parts with
little dimensional variations
A wide variety of shapes, sizes and complexity can
be produced by compression molding.
78.
79. DRAWBACKS
High tooling cost
Need for large heated presses.
Thus, this method is not practical for low volume
production.
81. Sheet moulding compound (SMC) or sheet
moulding composite is a ready to mould fibre-
reinforced polyester material primarily used in
compression moulding.
The sheet is provided in rolls weighing up to
1000 kg.
82.
83. SHEET MOULDING COMPOUND(SMC)
It refers to both material and process for producing
glass fiber reinforced polyester resin items .
SMC is a totally integrated compound in sheet form
that incorporates all reinforcements resin , chemical
thickness , fillers , mould release agents and other
ingredients .
Also includes pigments and shrink control agents
85. SHEET MOULDING COMPOUND(SMC
A SMC processing machine produces molding
compound in sheet form.
The glass fibre is added to a resin mixture that is
carried onto a plastic carrier film.
After partial cure, the carrier films are removed.
The sheet molding material is cut into lengths and
placed onto matched metal dies under heat and
pressure
87. ADVANTAGES OF SMC MOLDING PROCESS
High volume production.
Excellent part reproducibility.
Minimum material scrap.
Excellent design flexibility.
Parts consolidation.
88. BMC is a combination of chopped glass strands and Resin
in the form of a bulk pre-preg.
BMC is suitable for either compression or injection
molding.
Injection molding of BMC is used to produce complex
components such as electrical equipment, car
components, housings for electrical appliances and tools,
in large industrial volumes.
90. BULK MOULDING COMPOUND
Unlike SMC, it is not necessary to include a
maturation stage. Consequently, BMC pre-preg
formulations contain higher filler contents.
The chopped glass strands vary in length
depending on the level of performance required.
Reinforcement content generally ranges between
15 and 20 percent; however, it may reach 25
percent for the highest performance.
BMC uses a lower reinforcement content than SMC
and permits higher filler loadings with lower costs.
93. WET SYSTEM COMPRESSION MOULDING
Matrix ( Liquid Resin ) is pumped to dry
reinforcement in press mounted and heated
matched metal moulds
Hydraulic pressure forces the liquid resin to flow
through the reinforcement and hold the material in
place until cure is completed at the cure
temperature of 120C to 180C
94. WET SYSTEM COMPRESSION MOULDING
The equipment used for WCM is same as the BMC.
Matrix material is thermosetting polyester vinylester
and epoxy , resins filled with inert materials such as
clay , calcium carbonate and alumina , catalyst and
pigment to form a complete liquid system which
require only the addition of heat for curing
Reinforcement is chopped strand mats and
continuous strand mats
95. REINFORCED THERMOPLASTIC SHEET
COMPRESSION MOULDING
Utilizes precombined sheet of thermoplastic resin
and glass fiber reinforcement
These sheets are cut into blanks which are
preheated to a specified temperature and loded into
matched metal compression mould.
Under pressure , heat softened blanks flow and fill
the mould.
The mould is maintained at a temperature which
causes the sheet to solidify and allows demoulding
of the part
97. REINFORCED THERMOPLASTIC SHEET
COMPRESSION MOULDING
ADVANTAGES
Maximum design flexibility
Low capital cost
Tooling cost is low
Minimum material scrap
High volume production
98. REINFORCED THERMOPLASTIC SHEET
DISADVANTAGES
COMPRESSION MOULDING
DISADVANTAGES
Operater skill dependent
Lower impact resistance
Only one molded surface is obtained
Longer curig times required
101. INJECTION MOULDING
Injection molding is a manufacturing process for
producing parts from both thermoplastic and
thermosetting plastic materials.
102. INJECTION MOULDING
Material is fed into a heated barrel,
mixed, and forced into a mold cavity
where it cools and hardens to the
configuration of the cavity.
105. CLAMPING - the moving and
fixed platens of the injection
moulding machine holds the DWELLING - after the molten
mould tool together under plastic has been injected into the
pressure. mould pressure is applied to
ensure all cavities are filled.
INJECTION - the molten plastic COOLING - the plastic parts are
that has been melted from pellet then allowed to solidify in the
form in the barrel of the moulding mould.
machine is injected under
pressure into the mould.
106. OPENING - the moving platen moves away from the fixed platen separating
the mould tool.
EJECTION - rods, a plate or air blast then aids ejection of the completed
plastic moulding from the injection mould tool.
The length of time from closing the mould to ejecting the finished plastic
moulding is the cycle
107. PROCESS CHARACTERISTICS
Utilizes a ram or screw-type plunger to force molten
plastic material into a mold cavity .
Produces a solid or open-ended shape that has
conformed to the contour of the mold.
It is ideal for producing high volumes of the same
object
108. INJECTION MOULDING
wire spools, packaging, bottle caps,
automotive dashboards,
pocket combs,
, one-piece chairs and small tables,
storage containers,
mechanical parts (including gears),
and most other plastic products available today.
Injection molding is the most common method of
part manufacturing..[4].
109. ADVANTAGES OF INJECTION MOLDING
high production rates
repeatable high tolerances
the ability to use a wide range of materials
low labor cost
minimal scrap losses
little need to finish parts after molding
111. REACTION INJECTION MOLDING
It is similar to injection moulding except thermosetting
polymers which requires a curing reaction to occur
within the mold.
The RIM Process involves a chemical reaction between
the two liquid components. Initially, the liquids are held
in separate, temperature-controlled feed tanks. The
chemicals are fed through supply lines to metering units
that precisely meter both chemicals, at high pressure, to
a mixhead device.
113. RIM parts are created through a process that
begins when two liquid reactants - an Isocyanate
component and a Polyol resin mixture - are held in
separate tanks at an elevated temperature with
agitators.
These liquids are fed through supply lines at high
pressure to the mixhead.
114. When the injection begins, valves open in the
mixhead and the liquids enter a chamber in the
mixhead at high pressures (usually between 1,500
and 3,000 psi) and high speeds.
Here they are mixed by high-velocity
impingement.
From the mix chamber, the mixed liquid flows into
the mold at atmospheric pressure and undergoes
an exothermic chemical reaction, forming a polymer
in the mold.
115. Reaction time is usually expressed in seconds. For
extremely large parts the reaction time can be
extended to allow for proper filling of the mold.
116. ADVANTAGES
strong, flexible, lightweight parts which can easily
be painted.
The bi-component mixture injected into the mold
has a much lower viscosity than molten
thermoplastic polymers, therefore large, light-
weight, and thin-walled items can be successfully
RIM processed.
This thinner mixture also requires less clamping
forces, which leads to smaller equipment and
ultimately lower capital expenditures.
117. The disadvantages are slow cycle times, compared
to injection molding, and expensive raw materials.
