FIBER REINFORCED

PLASTICS (FRP)

Submitted by,

Menon Lakshmi Suresh

Divya C S

Amrutha K S

Lini cleetus C

DEFINITION

Fiber Reinforced Polymer (FRP)

Composites are defined as:

“A matrix of polymeric material that is

reinforced by fibers or other

reinforcing material”

Processes

• Matched die molding

• RTM

• Spray-up

• Hand lay-up

• Filament winding

• Pultrusion

• RIM

Benefits Of FRP

• HIGH STRENGTH/WEIGHT RATIO

• ORIENTATED STRENGTH

• DESIGN FLEXIBILITY

• LIGHTWEIGHT

• CORROSION RESISTANCE

• LOW MAINTENANCE/LONG-TERM DURABILITY

• LARGE PART SIZE POSSIBLE

• TAILORED AESTHETIC APPEARANCE

• DIMENSIONAL STABILITY

• LOW THERMAL CONDUCTIVITY

• LOW INSTALLED COSTS

FRP COMPOSITE

CONSTITUENTS

• RESINS (POLYMERS)

• REINFORCEMENTS

• FILLERS

• ADDITIVES

MATERIALS: RESINS

• PRIMARY FUNCTION:

“TO TRANSFER STRESS BETWEEN

REINFORCING FIBERS AND TO PROTECT

THEM FROM MECHANICAL AND

ENVIRONMENTAL DAMAGE”

• TYPES:

– THERMOSET

– THERMOPLASTIC

RESINS

THERMOSET THERMOPLASTIC

POLYESTER ACETAL

VINYL ESTER ACRYRONITRILE BUTADIENE

STYRENE (ABS)

EPOXY NYLON

PHENOLIC POLYETHYLENE (PE)

POLYURETHANE POLYPROPYLENE (PP)

POLYETHYLENE

TEREPHTHALATE (PET)

Matrix Materials – FRP

• Intermediate length fiber reinforcement

– The longer the fibers, the more difficult it is to coat the fibers

enough to reap strength benefits

– Low viscosity thermosets “wet-out” the materials better than high

viscosity thermoplastics

– Generally use unsaturated polyester and vinylester resins for

FRP

• Very long fibers or continuous fibers

– Typically used with thermosets, also for “wet-out” reasons

– Used generally in advanced composite parts and have greater

material property requirements

– Generally use epoxy resins

Reinforcements

• Three main types of fibers

– Fiberglass

– Carbon fiber or Graphite

– Organic fibers, aramids (kevlar)

• Hand lay-up technique is the simplest method of

composite processing.

• The processing steps are quite simple

First of all, mould is treated with a release agent-to prevent sticking

Gel coat layers are placed on the mold- to give decorative and protective surface

Put the reinforcement (woven rovings or chopped strand mat)

The thermosetting resin is mixed with a curing

agent, and applied with brush or roller on the

reinforcement

Curing at room temperature. After curing either

at room temperature or at some specific

temperature, mold is opened and the developed

composite part is taken out and further

processed.

Hand lay-up method finds application in many

areas like aircraft components, automotive parts,

boat hulls, diase board, deck etc.

• The schematic of hand lay-up is shown in figure

1.

Materials used

Matrix Epoxy, polyester, polyvinyl ester, phenolic

resin, unsaturated polyester, polyurethane

resin

Reinforcemen

t

Glass fiber, carbon fiber, aramid fiber,

natural plant fibers (sisal, banana, nettle,

hemp, flax etc.)

(all these fibers are in the form of

unidirectional mat, bidirectional (woven)

mat, stitched into a fabric form, mat of

randomly oriented fibers)

Raw materials used in hand lay-up method

Variation of hand lay-up

Mould is treated with a release agent-to prevent sticking

Gel coat layers are placed on the mold- to give decorative and protective surface

The gun sprays the mixture of chopped fiber, resin & catalyst on to a mould

Rolled out to remove entrapped air & give a smooth surface

Poor roll out can induce structural weakness by leaving air bubbles, dislocation of fibers and poor wet out

• Spray lay-up method is used for lower load carrying parts like small boats, bath tubs, fairing of trucks etc

Concept of spray-up process

Materials used

Matrix Epoxy, polyester, polyvinyl ester, phenolic

resin, unsaturated polyester, polyurethane

resin

Reinforcement Glass fiber, carbon fiber, aramid fiber,

natural plant fibers (sisal, banana, nettle,

hemp, flax, coir, cotton, jute etc.)

(all these fibers are in the form of

chopped short fibers, flakes, particle fillers

etc.)

Raw materials used in spray up method

[image courtesy:-www.engr.ku.edu]

RESIN TRANSFER MOLDING (RTM

Typical Preform Fiber Weaves

Polyester resins

Epoxy resins

Phenolic resins and other thermo set resins

Type of material for which process is used

RTM PROCESS

• impregnating preformed dry reinforcement in a

closed mold with wet thermosetting resin under

pressure

• production rate comparison

– 2 - 8 pph (parts per hour)

– spray-up @ 0.5 pph

– SMC, injection molding @ 30 pph (chopped fibers,

high pressures requires >>$ tooling)

REINFORCEMENTS RESINS

typeE-glass, S-glass

carbon/graphite

aramid

formmat

fabric

textile preform architecture

(knitted, braided, 3-D stitched)

preforms - preshaping of

reinforcement

Polyester

vinyl ester

epoxy

RTM EQUIPMENT

• resin/curing agent (catalyst) mixing equipment– positive displacement piston pumping cycle

– maintain accurate ratio control between resin and curing agent

– RTM process requires low injection pressures (30 psi - 100 psi)

– piston type positive displacement pumps are critical due to changing back pressure conditions - as resin is pushed through reinforcement an increasing back pressure builds against metering pumps - if slippage occurs at pump, resin/curing agent ratio will be affected

• with resin system components accurately metered, sent through flexible hoses to a mix head

MOLD DESIGN

• gasket around perimeter

• inlet injection port

– located at the lowest point of mold

– plug or check valve incorporated

• vent ports located at highest point of mold

• for high volume, tightly toleranced parts may use

press - controls parallelism of mold set during

opening and closing and holds mold closed

during injection (alternative is manually clamping

or fastening)

RTM PROCESS

• may or may not take place under vacuum (assists in minimizing air entrapment)

• mixer/injection head is inserted into mold

• injection pressure pushes check valve off its seat and allows resin to begin filling

• air is pushed ahead of resin

• resin will begin flowing from vent ports– if part design is simple may be full

– if part design complex, may require slight overfill to vent all air

• vent ports are pinched off and internal pressure causes inlet check valve to close

RTM PROCESS ISSUES

• critical to control infusion rate and flow front of

resin so that it infiltrates fiber preform evenly and

completely, but quickly before gelling

• resin is injected in center of part to guard against

formation of air pockets and minimize distance

resin must travel

• care must be exercised to insure reinforcement

does not move during injection (fiber wash)

ADVANTAGES DISADVANTAGES

- -Faster Production

Labor Savings

Dimensional Tolerances

Surface Finish

Lower Material Wastage

Very large and complex shapes can

made efficiently

Greater Tooling Design and

Construction Skills Required

Higher Tool Cost

Reinforcement loading may

be difficult with complex parts

Mold design is complex

ApplicationsWing Panel

Truck pannel

Aerospace parts

boat hulls

wind turbine blades

aircraft radar.

helmet, bathroom fixtures, car body etc

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FILAMENT WINDING

shaft

Filament Winding (one-step process)

-very high rate process

-Amenable to automated machine control

(little labor required)

-pressure bottle and cylindrical shapes

-rapidly growing variety applications

-continuous roving/yarns/strands

-Continuous filaments wound a mandrel(tool)

Major concerns in filament windings

-Resin selection

-Viscosity

-Need diluent or heat to lower viscosity

-Curing requirements

Fiber Requirements

-high tensile strength

-highest mechanical quality

-finishes to improve handling

REINFORCEMENTS RESINS

fiber in roving form

E-glass, S-glass

carbon/graphite

aramid

hybrids (within layer and

layer to layer)

wet or prepreg

epoxy

vinyl ester

polyester

Epoxy resins

Polyester resins

Phenolic resins

Silicone resins

29

Filament WindingsImpregnation methods

-Wet winding

-Fiber is impregnated immediately

-Most common in aerospace

-Most economical

Prepreg winding

- resin and fiber

combined in separate step

-better control

-better wet-out

-allows use of resin with

viscosities too high for wet

winding

Wind fibers are n two ways:

-planar winding: side by side no

cross over

-Helical winding: mandrel

moves while feeding

Filament Windings

Mandrel: can be in sections (removed piece by piece) can be salt or

sand (dissolved)

-after winding, product is cured on mandrel with heat alone (under

tension)

-tension can affect void content, resin content, thickness or part.

Filament Windings

32

Filament Windings

Characteristics of filament winding

-automation

-no prepreg step

-low labor cost

-high machine cost

Tape winding

-similar to filament winding except uses prepreg tape

-Wrapped around mandrel using rolling machine

-Used for golf clubs/pipes/tubes/fishing rods

ADVANTAGES DISADVANTAGES

-highly reproducible nature of the process

(layer to layer, part to part)

-continuous fiber over the entire part

high fiber volume is obtainable

-ability to orient fibers in the load direction

-fiber and resin used in lowest cost form

-autoclave not necessary

-a very fast and economic method

-Lack of ductility

-Low modulus of elasticity

-part configuration must facilitate mandrel

extraction (no trapped tooling)

-mandrel could be complex and expensive

-inability to wind reverse curvature

-inability to easily change fiber path within

one layer

-as wound external surface may not be

satisfactory for some applications

FILAMENT WINDING

APPLICATIONS

• surfaces of revolution

– cylinders, pipe or tubing

– spherical or conical

– pressure

• Storage tank

• Railway tank car

• Pipe

• Aerospace

Pultrusion

Pultrusion: a process for producing continuous length of shapes with a

constant cross section by pulling resin-impregnated fibers through a

heated die where curing occurs.

Characteristics

-Pultrusion produces parts with

-high fiber volume, high percentage of unidirectional

reinforcement.

-primarily a method for thermosetting resins

-one of few continuous FRP process

-Accounts for 3% of total FRP

-based on continuous fibers

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Pultrusion

Process Steps:

-String-up of desired fiber pattern

-Resin impregnation

-Preforming shape around mandrel (if necessary)

-Pre-heat (augmented cure)

-Cut finished part to length

-Speed: 0.5 to 10 ft/min

-Throughput: up to 4 lb/min

RESINS REINFORCEMENTS

polyesters

vinyl ester

Epoxies(aromatic

amine, anhydride

cures)

type

E-glass, S-glass

carbon/graphite

aramid

form

roving

mat

fabric

ADVANTAGES DISADVANTAGES

continuous process

-easy to automate, low labor

-High output; very long parts are

possible

-Uses inexpensive forms of

reinforcement

-Selective placement of reinforcement

relatively easy

-Low scrap

-Cross-sections must generally be

uniform

-difficult to maintain tight tolerances

-quick curing resin systems typically

have lower mechanical properties

-complexity of process

APPLICATIONS OF PULTRUSION

• Truck & bus components, such as body panels

and drive shaft

• Construction members such as building panels,

window & door frames, beams,pipes,cable trays

etc.

• Electrical equipment such as ladders,booms for

cherry picker trucks,tool handles etc.

• Sporting goods such as ski poles & fishing rods

Moulding Methods

Matched-die moulding

-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

mould and cures at high temp.

• Matched die or Compression molding

– Reduced flow path over injection or extrusion

– SMC compression molding allows for continuous

fibers, mats or weaves

– These processes offer parts that are finished on both

sides where most other composite processes do not

REACTION INJECTION MOULDING

RIM utilizes highly reactive two-component resins that are low-viscosity

liquids at room temperature

To initiate mixing and injection,the piston in the mixhead moves up and the

two resin components collide in the mixing chamber under high speed and

high pressure

The resin streams collide at 100-200m/s resulting in pressures of 10-40MPa

Following mold filling, the piston purges the mixhead of remaining resin

Since crosslinking is initiated by mixing and is very rapid,the resin gels

within seconds after the mold has been filled,paertially aided by heating of

the mould

To ensure complete crosslinking,it is important that exactly correct

proportions of resin components are mixed

DIAGRAM OF RIM

REINFORCED REACTION

INJECTION MOLDING

• Reinforced Reaction Injection Molding (RRIM) is

a process used to produce polyurethane and

polyurea thermoset polymers

• In RRIM short fibers are added to one of the

resin components prior to final resin mixing

• It has proved difficult to include fibers longer

than 0.5mm, since this leads to a too high

viscosity

• Although even such short fibers provide

significantly increased stiffness, damage

tolerance, dimensional tolerance and lower CTE

over what RIM components may offer, articles

produced through RRIM nevertheless have poor

structural properties from a composite view point

• This process is mainly used in automative

industry, where short cycle times and low labour

cost is important

STRUCTURAL REACTION

INJECTION MOLDING

• A subset of RIM is structural reaction injection molding (SRIM), which

uses fiber meshes for the reinforcing agent. The fiber mesh is arranged

in the mold and the polymer mixture is injection molded over it

• SRIM is the result of conceptually combining RTM and RIM

• In SRIM the reinforcement is first placed in the mold and following

mold closure the highly impingement-mixed resin is injected into the

mold to impregnate the reinforcement

• SRIM is used for long series where the significantly higher initial cost

for injection equipment may be written off

ADVANTAGES/DISADVANTAGE

S OF RIM PROCESS

– RIM resin builds viscosity rapidly (higher average viscosity during mold filling)

• applications must be simple geometries

• SRIM preform must be less complex and lower in reinforcement content

• parts do not normally flash out of mold parting line sufficiently to require sealing beyond metal land area or a pinch off around perimeter of part (low viscosity of RTM resin requires gasket or o-ring)

– highly reactive nature of RIM resin systems leads to cycle times currently faster than achieved with RTM process

– mix ratios of RIM resin systems nearly 1:1 in volume

• ideally suited to impingement mixing process

• self-cleaning mix element

• RTM ratios (as high as 100:1 by volume) require mixing in a static mixer and subsequent solvent flush

Applications

Roofs

Interior Panels

Energy Absorbing Bumpers

External Body Panels / Hoods / Air Deflectors

Fenders

Tractor Fender Deck

Or any other component that requires strength

and less weight