2. What is reinforced plastics?
Reinforced Plastics or RP is developed to produce an exceptionally strong and corrosive
materials.
The Reinforced Plastics products contains 10% to 40% of plastic.
In some cases plastic content may reach up to 60% or more.
3. Reinforced Plastics are also called plastic composites or composites.
Plastic composites are tailor-made which provide the designer and customers to have
engineered flexibility to meet different properties, environment and create different shapes.
4. 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.
• 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.
5. Materials used for Hand lay-up Method
Resins – Any, e.g. epoxy, polyester, vinyl ester, phenolic.
Fibers – Any, although heavy aramid fabrics can be hard to wet-out by hand.
Advantages:
• Widely used for many years.
• Simple principles to teach.
• Low cost tooling, if room-
temperature cure resins are used.
• Wide choice of suppliers and
material types.
• Higher fiber contents, and
longer fibers than with spray lay-
up.
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.
• 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.
• 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..
7. Spray up method
• Fiber is chopped in a hand-held gun and fed into a spray of catalyzed resin directed
at the mold. The deposited materials are left to cure under standard atmospheric
conditions. • Materials Options: Resins: Primarily polyester. Fibers: Glass roving
only.
• Advantages:
- Continuous process
- Any materials can be used as
mold.
- Error can be corrected by re-
spraying.
• Disadvantages:
- Slow.
- inconsistency.
- No control of fiber orientation. –
Only one side finished.
- Environmental unfriendly.
9. Pultrusion
• Fibers are pulled from a creel through a resin bath and then on through a heated
die.
• The die completes the impregnation of the fiber, controls the resin content and
cures the material into its final shape as it passes through the die.
• This cured profile is then automatically cut to length.
• Fabrics may also be introduced into the die to provide fiber
direction other than at 0°.
• Pultrusion is a continuous process, producing a profile of
constant cross-section, a variant known as 'pulforming' allows
for some variation to be introduced into the cross- section.
10. Main Advantages:
• This can be a very fast, and therefore economic,
way of impregnating and curing materials.
• Resin content can be accurately controlled.
• Fiber cost is minimized since the majority is
taken from a creel.
• Structural properties of laminates can be very
good since the profiles have very straight fibers
and high fiber volume fractions can be obtained.
• Resin impregnation area can be enclosed thus
limiting volatile emissions.
Main Disadvantages:
• Limited to constant or near
constant cross-section components
• Heated die costs can be high.
• Typical Applications: Beams and
girders used in roof structures,
bridges, ladders, frameworks.
12. Filament Winding
• This process is primarily used for hollow, generally circular or oval sectioned
components, such as pipes and tanks.
• Fiber tows are passed through a resin bath before being wound onto a mandrel
in a variety of orientations, controlled by the fiber feeding mechanism, and rate
of rotation of the mandrel.
Main Advantages
• This can be a very fast and therefore economic
method of laying material down.
• Resin content can be controlled by metering the
resin onto each fiber tow through nips or dies.
• Fiber cost is minimized since there is no
secondary process to convert fiber into fabric
prior to use.
• Structural properties of laminates can be very
good since straight fibers can be laid in a complex
pattern to match the applied loads.
Main Disadvantages
• The process is limited to convex shaped
components.
• Fiber 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
unmolded, and therefore cosmetically
unattractive.
• Low viscosity resins usually need to be used
with their attendant lower mechanical and
health and safety properties.
14. Resin transfer molding
• Resin transfer molding is a closed molding process
• In this technique, as the name indicates, resin is
transferred over the already placed reinforcement
• Reinforcement in terms of either woven mat or strand mat
form is placed on the surface of lower half mold.
• A release gel is applied on the mold surface for easy removal of the
composite.
• The mold is properly closed and clamped. The clamping can be
done either perimeter clamping or press clamping mechanism
• The resin is pumped into the mold through ports and air is
displaced through other vents
• After curing, the mold is opened and composite product is taken
out
15. Advantage
• Composite part produced with this method has
good surface finish on both side surface of the
product.
• Any combination of reinforced materials
(including 3D) in any orientation can be
achieved.
• Fast cycle time can be achieved through
temperature control tooling device.
• Process can be manual control, semi-automated
or highly automated.
• Composite part thickness is uniform which is
determined by the mold cavity.
• The process does not require high injection
pressure
Disadvantages
• Mold cavity limits the size of the
composite.
• High tooling cost.
• There is limitation on reinforcing
materials due to the flow and
resin saturation of fibers.
17. Reaction Injection Molding
• First, the two parts of the polymer are mixed together. The mixture is
then injected into the mold under high pressure using an impinging
mixer.
• The mixture is allowed to sit in the mole long enough for it to expand
and cure.
• If reinforcing agents are added to the mixture then the process is
known as reinforced reaction injection molding (RRIM).
• Common reinforcing agents include glass fibers and mica. This process
is usually used to produce rigid foam automotive panels
18. Advantage
• Reaction injection molding can produce strong,
flexible, lightweight parts which can easily be
painted
• It also has the advantage of quick cycle times
compared to typical vacuum cast materials.
• 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.
• Another advantage of RIM processed foam is
that a high- density skin is formed with a low-
density core.
Disadvantages
• slow cycle times, compared to
injection molding, and expensive
raw materials.
20. Matched-die molding
• The composite material is pressed between heated matched dies -Pressure required
depends on the flow characteristics of the feed materials - The feed materials flows into
the contours of the mold and cures at high temp.
There are two types of matched die forming:
• Sheet molding compound
• Dough/bulk molding compound (DMC)
- These two molding technique utilize same type of high pressure molding
equipment but differ in the form of the material that is placed inside the
mold to form the part
21. Sheet molding compound (SMC)
• Sheet of resin-fiber blend which contains additives (curing agent, release agent &
pigments). Clean to be used & give good consistency in properties b) Dough molding
compound (DMC) Blends (in dough forms) of all the necessary constituents (but only
short fibers are used)
• SMC molding is a sheet material that is made by chopped glass fibers on to a sheet of
plastic film on which a resin- initiator-filler mixture has been doctored • Another film
which also has the resin mixture applied onto it, is placed on the top and then the
sandwich of resin mixture and the chopped glass is passed between the compaction rolls
to wet the fibers and mix the constituents
• The material is then cured and rolled up for shipment, A typical SMC incorporates
about 30- 50%fibres ,25%resin,25-45% filler.
22. Bulk Molding Compound
• BMC is a dough like mixture of chopped fiberglass resin initiator and fillers
that has a composition similar to that of SMC
• The resulting material is called a premix
• The fiberglass mixture is about 5-10% lower than SMC
• BMC is molded by placing a weighed amount of material onto the lower mold
• The mod are then closed under pressure ,temperature
Advantages
• Both interior and exterior surfaces
are finished
• Production rate can be high
• Labor cost are low
• Minimum trimming of parts are
molded
• Product has good mechanical
properties and closed part tolerance
Disadvantages
• More equipment is needed than layup
• Mold and tooling are costly than layup molds
• Transparent parts are not possible with
SMC and BMC
• Molding problems may cause surface
imperfections
• SMC and BMC have limited shelf life
