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BMM 3643 Page 2
Lesson Outcomes:
After todays lecture, students areexpected to:
Analyze the process of elastomer
and polymer composite production,metal-matrix composite processes
Analyze the design considerationsfor plastics technology
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BMM 3643 Page 3
Processing Elastomers
Commonly shaped by extrusion orinjection moulding.
Extruded parts such as tubing, hoses &inner tubes.
Injection-moulded parts mostly used forautomobiles.
Also can be shaped by blow moulding &thermoforming.
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Calendering
For rubber & some thermoplastic sheet.
A warm mass of the compound is fedinto a series of rolls and then strippedoff in the form of a sheet.
Sheets produced are subsequently usedin thermoforming.
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BMM 3643 Page 5
Calendering
Schematic illustration of calendering. Sheets produced by this process
subsequently are used in thermoforming. The process also is used in
the production of various elastomer and rubber products.
BMM 3643 Page 6
Dipping
Discrete rubberproduct likesglove.
Metal form
repeatedlydipped into aliquid compound.
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BMM 3643 Page 7
ProcessingReinforcedPlastics
To obtain good bonding between thereinforcing fibers and the polymermatrix, fibers surface treated byimpregnation (sizing).
Short fibers added to thermoplastics forInjection moulding.
Long fibers used in the compressionmoulding.
Partially cured sheets called by variousterms such as;
BMM 3643 Page 8
1. Prepregs The continuous fibers aligned. Through surface treatment to
enhance adhesion to the matrix.
Individual sheet combined intolaminated structures Eg : Stabilizer for the jet fighter Typical products from prepreg are
panels for construction and electricalinsulation.
ProcessingReinforcedPlastics (cont.)
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BMM 3643 Page 9
Tapes used inMaking ReinforcedPlastic Parts
(a) Manufacturing process for polymer-matrix composite tape. (b) Boron-epoxy prepregtape. These tapes are then used in making reinforced plastic parts and components with
high strength-to-weight ratios, particularly important for aircraft and aerospace applications
and sports equipment. Source: (a) Courtesy of T. W. Chou, R. L. McCullough, and R. B.
Pipes. (b) Courtesy of Avco Specialty Materials/Textron.
(b)
BMM 3643 Page 10
Tape and Tape-Laying System
(b)(a)
(a) Single-ply layup of boron-epoxy tape for the horizontal stabilizer for an F-14 fighter
aircraft. (b) A 10-axis computer-numerical-controlled tape-laying system. This machine
is capable of laying up 75- and 150-mm (3- and 6-in.) wide tapes on contours of up to +/-
30 degrees and at speeds of up to 0.5m/s (1.7 ft/s). Source: (a) Courtesy of Grumman
Aircraft Corporation. (b) Courtesy of The Ingersoll Milling Machine Company.
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BMM 3643 Page 11
ProcessingReinforcedPlastics (cont.)
Forms of fibreglass (a) continuous strand roving (b)chopped strand (c) chopped strand mat (d) wovenroving
BMM 3643 Page 12
Production of Fiber-ReinforcedPlastic Sheets
Schematic illustration of the manufacturing process for producing fiber-reinforced
plastic sheets. The sheet still is viscous at this stage and later can be shped into
various products. Source: After T. W. Chou, R. L. McCullough, and R. B. Pipes.
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BMM 3643 Page 13
2. Sheet moulding compound(SMC) Chopped fibers deposited in random
directions over a layer of resin paste. Second layer of resin paste is deposited on
top, then pressed between rollers.
3. Bulk moulding compound (BMC)
The compounds are in the shape of billets
ProcessingReinforcedPlastics (cont.)
BMM 3643 Page 14
4. Thick moulding compound (TMC) Combines a characteristics of lower cost
BMC & higher strenghth SMC
ProcessingReinforcedPlastics (cont.)
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BMM 3643 Page 15
Moulding of Reinforced Plastics
Common moulding processes forreinforced plastics are;
1. Compression moulding Material placed between two moulds and
pressure is applied.
2. Vacuum-bag moulding/Pressure Prepregs are laid in the mould
Pressure to shape the product obtained bycovering the lay-up with a plastic bag andcreating a vacuum
BMM 3643 Page 16
Vacuum-Bag Forming andPressure-Bag Forming
Schematic illustration of (a) vacuum-bag forming, and (b) pressure-bag
forming. These processes are used in making discrete reinforced plastic
parts. Source: After T. H. Meister.
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BMM 3643 Page 17
3. Contact moulding (Open mouldprocessing) Used in making products with high surface-
area-to-thickness ratios. Use a single male or female mould. Can be done by hand lay-up or spray lay-
up.
Moulding of Reinforced Plastics(cont.)
BMM 3643 Page 18
Open-Mold Processing
Manual methods of processing reinforcedplastics: (a) hand lay-up, and (b) spray
lay-up. Note that, even though the
process is slow, only one mold is
required. The figures show a female
mold, but male molds also are used.
These methods also are called open-mold
processing. (c) A boat hull made by
these processes.
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BMM 3643 Page 19
Some other processes for reinforcedplastics are:
1. Filament Winding Resin and fibers are combined at the time
of curing Parts are formed on a rotating mandrel The reinforcing filament, tape is wrapped
continuously around the mandrel. Products example: pressure vessel,propellers, blades
ProcessingReinforcedPlastics (cont.)
BMM 3643 Page 20
Filament-Winding
(b)
(a) Schematic illustration of the filament-winding process; (b) fiberglass being
wound over aluminum liners for slide-raft inflation vessels for the Boeing 767
aircraft. The products made by this process have high strength-to-weight ratio and
also serve as lightweight pressure vessels. Source: Courtesy of Brunswick
Corporation.
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BMM 3643 Page 21
2. Pultrusion Produces long parts with various uniform
cross-section such as rod, flat strips andtubing.
Continuous reinforcement is suppliedthrough bobbins (prepreg feed system)
The bundle is mixed with a thermosettingbath then a performing die and a heated
steel die. The product is cured then.
ProcessingReinforcedPlastics (cont.)
BMM 3643 Page 22
Pultrusion
(a) Schematic illustration of the pultrusion process. (b) Examples of parts
made by pultrusion. The major components of fiberglass ladders (used
especially by electricians) are made by this process. Unlike aluminum
ladders, they are available in different colors but are heavier because of the
presence of glass fibers. Source: Courtesy of Strongwell Corporation.
(b)
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BMM 3643 Page 23
Metal matrix-compostie can be made bythe following processes:
1. Liquid-phase processing Casting involving liquid-matrix material
(aluminium, titanium) and solid reinfoircement(graphite, SiC, Al2O3)
2. Solid-phase processing
Powder-metallurgy techniques including coldand hot isostatic pressing.
Products examples, tungsten-carbide tools anddies with cobalt as the matrix.
Processing Metal-matrixComposite
BMM 3643 Page 24
Design Considerations ofplastics
Considerations for product design: Material selection to meet product
requirements
Product without stress concentration, sink
marks, ... Position of gate, runner, ejection pin for
tool design,
Elimination of premature failures based onliterature reviews.
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BMM 3643 Page 25
Considerations for tool design:
Tool material for manufacturing volumeand life
Tonnage of press & number of cavities in atool
Position of gate, runner, ejection pin for
tool design, ...
Design Considerations of plastics(cont.)
BMM 3643 Page 26
Design Modifications to MinimizeDistortion in Plastic Parts
Examples of design modifications to eliminate or minimize distortion in plastic parts:
(a) suggested design changes to minimize distortion; (b) stiffening the bottoms of
thin plastic containers by dominga technique similar to the process used to shape
the bottoms of aluminum beverage cans; and (c) design change in a rib to minimize
pull-in (sink mark) caused by shrinkage during the cooling of thick sections in
molded parts.
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Avoid sharp variation of wall thickness Avoid sharp corners
Example of Design Considerationsfor Plastics Processing
Provide generous draft angles, 5o or more
Avoid needs of side-pull (reading assignment)
Example of Design Considerationsfor Plastics Processing
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Core bosses to ensure uniform thickness (minimize impact ofvariable shrinkage)
Example of Design Considerationsfor Plastics Processing
Thats all for today..
Any questions??
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IQ + EQ + SQ = TQ
Thank You for coming and
see you again..