This is about the manufacturing of composites.

2. PROCESSING TECHNIQUES
 Structural: continuous aligned fibres
 Semi structural: continuous non aligned fibres
 Non structural: discontinuous fibres (Covering,
protecting, a coating or a box closure-
discontinuous fiber)
 Primarily classified as
Sheet Molding Compound (SMC)
Bulk Molding Compound (BMC)

3. PMC MANUFACTURING PROCESS

4. Comparison between thermoplastics and thermosets

5.  Open mould processes (Hand lay up)
 Closed mould processes (Resin Transfer Molding)
 Continuous processes (Pultrusion)
Resin Transfer Molding
Hand lay up Pultrusion
TYPES OF MANUFACTURING PROCESSES

6.  Production rate
 Cost of production
 User requirements
 Performance requirements
 Total production volume
 Size of the parts
 Strength of the parts
 Surface finish of the final product
 Geometry of the product
 Material
 Factors Affecting Fabrication
Processes
FACTORS AFFECTING FABRICATION PROCESSES
 The automobile market requires a high rate of production.
For example, 10000 units per year (40 per day) to 5000000
per year ( 20000 per days)
 In the aerospace market, production requirements are usually
in the range of 10 to 100 per year
 Hand lay-up and wet lay-up processes cannot be used for
high volume production.
 Compression molding and injection molding are used to
meet high-volume production needs.
 Cost
 Tooling
 Labor
 Raw materials
 Process cycle time
 Assembly time

7. FABRICATION PROCESSES OF FIBROUS COMPOSITES
 HAND LAY-UP
 SPRAY LAY-UP
 AUTOCLAVE CURING
 PULTRUSION
 RESIN TRANSFER MOLDING - RTM
 FILAMENT WINDING
 COMPRESSION MOLDING
 INJECTION MOLDING
 BLOW MOLDING
 INFILTRATION

8.  Advantages:
 The process results in low cost tooling with the use of room-
temperature cure resins.
 The process is simple to use.
 Any combination of fibres and matrix materials are used.
 Higher fibre contents and longer fibres as compared to other
processes.
 Disadvantages:
 Since the process is worked by hands, there are safety and
hazard considerations.
 The resin needs to be less viscous so that it can be easily worked
by hands.
 The quality of the final product is highly skill dependent of the
labours.
 Uniform distribution of resin inside the fabric is not possible.
 It leads to voids in the laminates.
 Possibility of diluting the contents.
 Applications:
 The process is suitable for the fabrication of wind-turbine blades, boats and architectural mouldings.
HAND LAY-UP
 The mold is coated by a release anti-adhesive agent, preventing
sticking the molded part to the mold surface.
 The prime surface layer of the part is formed by applying gel
coating.
 A layer of fine fiber reinforcing tissue is applied.
 Layers of the liquid matrix resin and reinforcing fibers in form of
woven fabric, rovings or chopped strands are applied. The resin
mixture may be applied by either brush or roll.
 The part is cured (usually at room temperature).
 The part is removed from the mold surface.

9. SPRAY LAY-UP
 The spray-up process offers the following advantages:
 It is suitable for small to medium-volume parts.
 It is a very economical process for making small to large parts.
 It utilizes low-cost tooling as well as low-cost material systems.
 It is not suitable for making parts that have high structural requirements.
It is difficult to control the fiber volume fraction as well as the thickness.
 The process offers a good surface finish on one side and a rough surface finish
on the other side.
 The process is not suitable for parts where dimensional accuracy and process
repeatability are prime concerns.
 The spray-up process does not provide a good surface finish.
 Only short fibres can be used in this process.
 Similar to wet/hand lay-up process, the resins need to be of low viscosity so
that it can be sprayed.
 Simple enclosures, lightly loaded structural panels, e.g. caravan bodies, truck fairings, bathtubs, shower trays, some
small dinghies.
 Advantages:
 Disadvantages:
 Applications:

10.  Large components can be fabricated.
 Since, the curing of matrix material is carried out under controlled
environment, the resin distribution is better as compared to hand or spray
lay-up processes.
 Less possibility of dilution with foreign particles.
 Better surface finish.
 Advantages:
 Initial cost of tooling is high.
 Running and maintenance cost is high.
 Not suitable for small products.
 Disadvantages:
 The process is suitable for aerospace, automobile parts like wing
box, chassis, bumpers, etc
 Applications:
AUTOCLAVE CURING
Autoclave Curing is a method in which a part, molded by one of the open molding methods, is cured by a subsequent application of
vacuum, heat and inert gas pressure.
 The molded part is first placed into a plastic bag, from which air is exhausted by a vacuum pump. This operation removes air
inclusions and volatile products from the molded part.
 Then heat and inert gas pressure are applied in the autoclave causing curing and densification of the material.
 Autoclave Curing enables fabrication of consistent homogeneous materials. The method is relatively expensive and is used for
manufacturing high quality aerospace products.

11.  The process is suitable for mass production.
 The process is fast and economic.
 Resin content can be accurately controlled.
 Fibre cost is minimized as it can be taken directly from a creel.
 The surface finish of the product is good.
 Structural properties of product can be very good as the
profiles have very straight fibres.
 Advantages:
 Limited to constant or near constant cross-section components.
 Heated die costs can be high.
 Products with small cross-sections alone can be fabricated.
 Disadvantages:
 Beams and girders used in roof structures, bridges,
ladders, frameworks
 Applications:
PULTRUSION
Pultrusion is an automated, highly productive process of fabrication of Polymer Matrix Composites in form of continuous long
products of constant cross-section.
Pultrusion process involves the following operations:
1.Reinforcing fibers are pulled from the creels. Fiber (roving) creels
may be followed by rolled mat or fabric creels. Pulling action is
controlled by the pulling system.
2.Guide plates collect the fibers into a bundle and direct it to the resin
bath.
3.Fibers enter the resin bath where they are wetted and impregnated
with liquid resin. Liquid resin contains thermosetting polymer, pigment,
fillers, catalyst and other additives.
4.The wet fibers exit the bath and enter preformer where the excessive
resin is squeezed out from fibers and the material is shaped.
5.The preformed fibers pass through the heated die where the final
cross-section dimensions are determined and the resin curing occurs.
6.The cured product is cut on the desired length by the cut-off saw.

12.  The process is very efficient.
 Suitable for complex shapes.
 High fibre volume laminates can be obtained with very low void contents.
 Good health and safety, and environmental control due to enclosure of resin.
 Possible labour reductions.
 Both sides of the component have a moulded surface. Hence, the final
product gets a superior surface finish
 Better reproducibility.
 Relatively low clamping pressure and ability to induce inserts.
 Advantages:
 Matched tooling is expensive and heavy in order to withstand pressures.
 Generally limited to smaller components.
 Unimpregnated areas can occur resulting in very expensive scrap parts.
 Disadvantages:
 Hollow cylindrical parts like motor casing, engine covers, etc.
 Applications:
RESIN TRANSFER MOLDING - RTM
Resin Transfer Molding is a process in which a pre-weighed amount of a polymer is preheated in a separate chamber (transfer
pot) and then forced into a preheated mold through a sprue, taking a shape of the mold cavity and performing curing due to heat
and pressure applied to the material.
The method is used primarily for molding thermosetting resins (thermosets), but some thermoplastic parts may also be produced
by Transfer Molding.

13.  Resin content is controlled by nips or dies.
 The process can be very fast.
 The process is economic.
 Complex fibre patterns can be attained for better load bearing of the structure.
 Advantages:
 Resins with low viscosity are needed.
 The process is limited to convex shaped components.
 Fibre cannot easily be laid exactly along the length of a component.
 Mandrel costs for large components can be high.
 The external surface of the component is not smoothly finished.
 Disadvantages:
 Pressure bottles, rocket motor casing, chemical storage tanks, pipelines,
gas cylinders, fire fighters, breathing tanks etc.
 Applications:
FILAMENT WINDING
Filament Winding method involves a continuous filament of reinforcing material wound onto a rotating mandrel in layers at
different layers. If a liquid thermosetting resin is applied on the filament prior to winding the, process is called Wet Filament
Winding. If the resin is sprayed onto the mandrel with wound filament, the process is called Dry Filament Winding.

14.  Good surface finish on both sides
 Faster production
 Low cost
 More uniform density
 Uniform shrinkage due to uniform flow
 Improved impact strength due to no degradation of fibers
during flow
 Dimensional accuracy
 Internal stressed and warping are minimized
 Less labor requirement
 Advantages:
 Curing time large
 Uneven parting lines present
 Not suitable for low volume production because of high
investment needed for dies and press
 Not suitable to produce very large-sized products
 Scrap cannot be reprocessed
 Disadvantages:
Appliance housing , Radio cases, Automotive exterior panels,
Electrical parts
 Applications:
COMPRESSION MOLDING
Compression Molding is a process in which a molding polymer is squeezed into a preheated mold taking a shape of the mold
cavity and performing curing due to heat and pressure applied to the material. The method is used mostly for molding
thermosetting resins (thermosets), but some thermoplastic parts may also be produced by Compression Molding.

15. INJECTION MOLDING
Advantages:
 Mass Production
 Design Flexibility
 Produce the complex product in different shapes and designs
 Labor Cost will be low
 Waste of Material Very Low
Disadvantages:
 Expensive Tooling Investment
 Inflexibility once the tool has been produced
 Surface Defects (such as blemishes and sink marks)
 Thermal Expansion Issues (primarily on materials with high
shrink rates)
Applications of plastic injection Molding
 Mechanical Parts (Gears)
 automotive parts and components
 storage containers
 tables
 wire spools
 bottle caps
Injection Molding is a process in which molten polymer is
forced under high pressure into a mold cavity through an opening
(sprue).
The plastic injection molding process cycle in 9 steps:
1.Material enters the barrel
2.Material melts and mixes
3.Volume of material (Shot sizes in barrel is created)
4.Mold closes
5.Injection of the plastic into the mold cavity
6.Molten material cooled (during this process, steps 1-3 are preparing for
next cycle)
7.Mold opens
8.Part ejects
9.Return to Step 4 for the next cycle

16. BLOW MOLDING
Blow Molding is a process in which a heated hollow thermoplastic tube (parison) is inflated into a closed mold conforming the
shape of the mold cavity.
 The parison is extruded vertically in downward direction between two mold
halves.
 When the parison reaches the required length the two mold halves close
resulting in pinching the top of parison end and sealing the blow pin in the
bottom of the parison end.
 Parison is inflated by air blown through the blow pin, taking a shape
conforming that of the mold cavity. The parison is then cut on the top.
 The mold cools down, its halves open, and the final part is removed.
Advantage:
•Low tooling cost
•Fast production rate.
•Ability to mold complex.
•Little scrap generated.
•Recycling.
•Large hollow parts.
Disadvantage:
•Only for hollow parts .
•Defect may be seen .
•Thick parts can not be manufectured.

17. INFILTRATION
Infiltration is a liquid state method of composite materials fabrication, in which a preformed dispersed phase
(ceramic particles, fibers, woven) is soaked in a molten matrix metal, which fills the space between the dispersed
phase inclusions.
Squeeze Casting Infiltration process has the following steps:
•A preform of dispersed phase (particles, fibers) is placed into the
lower fixed mold half.
•A molten metal in a predetermined amount is poured into the lower
mold half.
•The upper movable mold half (ram) moves downwards and forces
the liquid metal to infiltrate the preform.
•The infiltrated material solidifies under the pressure.
•The part is removed from the mold by means of the ejector pin.
The method is used for manufacturing simple small parts (automotive
engine pistons from aluminum alloy reinforced by alumina short
fibers).

18. Links
http://www.substech.com/dokuwiki/doku.php?id=composites