slide polymer matrix (2)
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PROCESSING OF POLYMER MATRIX COMPOSITES
GROUP 4NOORHAFIZAH BT MOHD YUSOFF
NUR AMIRA BT MAHMUDNURUL FARAHAH BT ADENAN
FATIN NADZIRAH BT SABRISITI MUNIRAH BT ABD RASHID
MATRICES COMPOSITE MATERIALS
FIBRES
Polymer Matrix Thermosetting (TS) polymers are the
most common matrix materials Principal TS polymers are:
Phenolics – used with particulate reinforcing phases
Polyesters and epoxies - most closely associated with PMCs
Thermoplastic molding compounds include fillers or reinforcing agents
Nearly all rubbers are reinforced with carbon black
MATERIAL SUITABILITYDepending on the applications.Not all materials are suitable for all applications.
Knows the pros and cons of the materials before using it for certain applications.
Factors to be consider :-Structural (stiffness, strength,
toughness)Thermal Electrical (conduct electricity or
not ?)Chemical (resistance)Aesthetic (will the materials
achieve the required look?)
FACTORS IN PROCESS SELECTION• Materials – matrix and
reinforcing(fibres) system• Reinforcing architecture required• Complexity of part geometry• Number to be manufactured• How quickly they are to be
manufactured
OPEN MOULDING
CLOSED MOULDING
Open Mold PMC Processes1. Hand lay‑up 2. Spray‑up3. Vacuum Bagging – uses hand-lay-up, uses
atmospheric pressure to compact laminate.
4. Filament Winding The differences are in the methods of
applying the laminations to the mold, alternative curing techniques, and other differences
Open Mold ProcessesFamily of FRP shaping processes that use a
single positive or negative mold surface to produce laminated FRP structures
The starting materials (resins, fibers, mats, and woven rovings) are applied to the mold in layers, building up to the desired thickness
This is followed by curing and part removal Common resins are unsaturated polyesters
and epoxies, using fiberglass as the reinforcement
Hand Lay‑Up MethodOpen mold shaping method in which
successive layers of resin and reinforcement are manually applied to an open mold to build the laminated PMC composite structure
Labor‑intensive Finished molding must usually be trimmed
with a power saw to size outside edgesOldest open mold method for PMC
laminates
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.
Hand Lay-Up Method
Products Made by Hand Lay‑Up Generally large in size but low in production
quantity - not economical for high production
Applications:Boat hullsSwimming poolsLarge container tanksMovie and stage propsOther formed sheets
SPRAY UPSuitable in making boats, transportation
components, tub/shower units in a large variety of shapes and sizes.
Chopped laminated – good comfortability and faster than hand lay-up.
Operator – control thickness and consistency
Operator dependant compared to hand lay-up.
Low production per volume but can produce more when using multiple molds.
Spray‑Up MethodLiquid resin and chopped fibers are sprayed
onto an open mold to build successive FRP laminations
Attempt to mechanize application of resin‑fiber layers and reduce lay‑up time
Alternative for step (3) in the hand lay‑up procedure
Figure 15.5 Spray‑up method
Spray-Up Method
Products Made by Spray‑UpBoat hulls, bathtubs, shower stalls,
automobile and truck body parts, recreational vehicle components, furniture, large structural panels, and containers
Movie and stage props are sometimes made by this method
Since products made by spray‑up have randomly oriented short fibers, they are not as strong as those made by lay‑up, in which the fibers are continuous and directed
Vacuum Bagging
Use atmospheric pressure to suck air from under vacuum bag, to compact composite layers down and make a high quality laminate (image from cgi.ebay.com).
Layers from bottom include: mold, mold release, composite, peel-ply, breather cloth, vacuum bag, also need vacuum valve, sealing tape.
Filament WindingResin‑impregnated continuous fibers are
wrapped around a rotating mandrel that has the internal shape of the desired PMC 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
Figure 15.8 Filament winding.
Filament Winding
Closed Mold ProcessesPerformed in molds consisting of two
sections that open and close each molding cycle
Tooling cost is more than twice the cost of a comparable open mold due to the more complex equipment required in these processes
Classification of Closed Mold Processes Three classes based on their counterparts
in conventional plastic molding: 1. Compression molding2. Transfer molding3. Injection molding4. Resin transfer molding5. Pultrusion
The terminology is often different when polymer matrix composites are molded
Compression Molding PMC ProcessesA charge is placed in lower mold section, and
the sections are brought together under pressure, causing charge to take the shape of the cavity
Mold halves are heated to cure TS polymer When molding is sufficiently cured, the mold
is opened and part is removed Several shaping processes for PMCs based
on compression moldingThe differences are mostly in the form of the
starting materials
Injection Molding PMC ProcessesInjection molding is noted for low cost
production of plastic parts in large quantities
Although most closely associated with thermoplastics, the process can also be adapted to thermosets
Processes of interest in the context of PMCs:Conventional injection moldingReinforced reaction injection molding
Pultrusion ProcessesSimilar to extrusion (hence the name similarity)
but workpiece is pulled through die (so prefix "pul‑" in place of "ex‑")
Like extrusion, pultrusion produces continuous straight sections of constant cross section
Developed around 1950 for making fishing rods of glass fiber reinforced polymer (GFRP)
A related process, called pulforming, is used to make parts that are curved and which may have variations in cross section throughout their lengths
PultrusionContinuous fiber rovings are dipped into a
resin bath and pulled through a shaping die where the impregnated resin cures
The sections produced are reinforced throughout their length by continuous fibers
Like extrusion, the pieces have a constant cross section, whose profile is determined by the shape of the die opening
The cured product is cut into long straight sections
Figure 15.11 Pultrusion process
Pultrusion Process
Materials and Products in PultrusionCommon resins: unsaturated polyesters,
epoxies, and silicones, all thermosetting polymers
Reinforcing phase: E‑glass is most widely, in proportions from 30% to 70%
Products: solid rods, tubing, long flat sheets, structural sections (such as channels, angled and flanged beams), tool handles for high voltage work, and third rail covers for subways.
Resin Transfer Molding (RTM)intermediate volume molding process inject resin under pressure into a mold
cavitycan be automated and is capable of
producing rapid cycle timesVacuum assist can be used to enhance
resin flow in the mold cavity.
resin is injected under pressure, using mix/meter injection equipment, and the part is cured in the mold
The reinforcement can be either a preform or pattern cut roll stock material
can be done at room temperatureproduces parts with two finished surfaces.laying up reinforcement material dry inside
the mold, any combination of materials and orientation can be used, including 3-D reinforcements
Part thickness is determined by the tool cavity
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