slide polymer matrix (2)

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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