Composite Lecture Main

8/8/2019 Composite Lecture Main

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COMPOSITECOMPOSITEMATERIALSMATERIALS


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COMPOSITESCOMPOSITES--Composite materialsComposite materials are engineered materials madeare engineered materials made

from two or more constituent materials that remainfrom two or more constituent materials that remain

separate and distinct while forming a single componentseparate and distinct while forming a single component

--Generally, one material forms a continuous matrix whileGenerally, one material forms a continuous matrix whilethe other provides the reinforcementthe other provides the reinforcement

-- The two materials must be chemically inert with respectThe two materials must be chemically inert with respect

to each other so no interaction occurs upon heating untilto each other so no interaction occurs upon heating until

one of the components melts, an exception to thisone of the components melts, an exception to this

condition is a small degree ofcondition is a small degree of interdiffusioninterdiffusion at theat the

reinforcementreinforcement--matrix interface to increase bondingmatrix interface to increase bonding


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COMPOSITESCOMPOSITES

Composites can be found in:Composites can be found in:--Boat hullsBoat hulls

--The aerospace industry (structural components as wellThe aerospace industry (structural components as wellas engines and motors)as engines and motors)

--Automotive parts (panels, frames, dashboards, bodyAutomotive parts (panels, frames, dashboards, bodyrepairs)repairs)

--Sinks, bathtubs, hot tubs, swimming poolsSinks, bathtubs, hot tubs, swimming pools

--Cement buildings, bridgesCement buildings, bridges

--Surfboards, snowboards, skisSurfboards, snowboards, skis

--Golf clubs, fishing poles, hockey sticksGolf clubs, fishing poles, hockey sticks--Trees are technically composite materials, plywoodTrees are technically composite materials, plywood

--Electrical boxes, circuit boards, contactsElectrical boxes, circuit boards, contacts

--EverywhereEverywhere


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Composites can be classified by theirComposites can be classified by their

matrix material which include:matrix material which include:

--Metal matrix composites (MMCs)Metal matrix composites (MMCs)

--Ceramic matrix composites (CMCs)Ceramic matrix composites (CMCs)

--Polymer matrix composites (PMCs) orPolymer matrix composites (PMCs) or

sometimes referred to as organic matrixsometimes referred to as organic matrix

composites (OMCs)composites (OMCs)


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MMCMMC -- Metal Matrix CompositesMetal Matrix Composites--The matrix is relatively soft and flexible.The matrix is relatively soft and flexible.

--The reinforcement must have high strength and stiffnessThe reinforcement must have high strength and stiffness

--Since the load must be transferred from the matrix to theSince the load must be transferred from the matrix to the

reinforcement, the reinforcementreinforcement, the reinforcement--matrix bond must be strong.matrix bond must be strong.

MMC use:MMC use:

--Two types of particulates ( dispersion strengthened alloysTwo types of particulates ( dispersion strengthened alloys

and regular particulate composites)and regular particulate composites)

--Or long fiber reinforcementsOr long fiber reinforcements


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PMCPMC -- Polymer Matrix CompositesPolymer Matrix Composites--The matrix is relatively soft and flexibleThe matrix is relatively soft and flexible

--The reinforcement must have high strength and stiffnessThe reinforcement must have high strength and stiffness

--Since the load must be transferred from matrix toSince the load must be transferred from matrix to

reinforcement, the reinforcementreinforcement, the reinforcement--matrix bond must be strongmatrix bond must be strong

CMCCMC Ceramic Matrix CompositesCeramic Matrix Composites

--The matrix is relatively hard and brittleThe matrix is relatively hard and brittle

--The reinforcement must have high tensile strength to arrestThe reinforcement must have high tensile strength to arrest

crack growthcrack growth

--The reinforcement must be free to pull out as a crack extends,The reinforcement must be free to pull out as a crack extends,

so the reinforcementso the reinforcement--matrix bond must be relatively weakmatrix bond must be relatively weak


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Classification based onClassification based on

reinforcementreinforcement FibreFibre reinforced compositesreinforced composites

Particle reinforce compositesParticle reinforce composites

Structural compositesStructural composites Hybrid compositesHybrid composites


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Types of Composite MaterialsTypes of Composite Materials

There are five basic types of composite materials:There are five basic types of composite materials: FiberFiber,,

particleparticle,, flakeflake,, laminarlaminaror layered andor layered and filledfilled composites.composites.


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FIBER REINFORCEDFIBER REINFORCED

COMPOSITESCOMPOSITES--Fiber reinforced composites provide improved strength,Fiber reinforced composites provide improved strength,

fatigue resistance, Youngs modulus and strength tofatigue resistance, Youngs modulus and strength toweight ratio over the constituent materials.weight ratio over the constituent materials.

--This is achieved by incorporating strong, stiff, yet brittleThis is achieved by incorporating strong, stiff, yet brittlefibers into a more ductile matrix.fibers into a more ductile matrix.

--Generally speaking the fiber supplies the strength andGenerally speaking the fiber supplies the strength andstiffness while the matrix binds the fibers together andstiffness while the matrix binds the fibers together and

provides a means of transferring the load between fibersprovides a means of transferring the load between fibers

--The matrix also provides protection for the fibersThe matrix also provides protection for the fibers


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CHARACTERISTICS OFFIBERCHARACTERISTICS OFFIBER

REINFORCED COMPOSITESREINFORCED COMPOSITES

--Many factors must be considered when designing a fiberMany factors must be considered when designing a fiber--

reinforced composite including the length, diameter, orientation,reinforced composite including the length, diameter, orientation,amount and properties of the constituents, and the bondingamount and properties of the constituents, and the bonding

between them.between them.

--The method used to produce the final product is also veryThe method used to produce the final product is also very

important as it dictates the type of properties just mentioned asimportant as it dictates the type of properties just mentioned as

well as the quality of the product.well as the quality of the product.


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CHARACTERISTICS OFFIBERCHARACTERISTICS OFFIBER

REINFORCED COMPOSITESREINFORCED COMPOSITESFiber length and diameter: Fiber dimensions are characterized byFiber length and diameter: Fiber dimensions are characterized by

their aspect ratiotheir aspect ratio l/dl/dwherewhere ll is the fiber length andis the fiber length and dd is theis the

diameter.diameter.The strength improves when the aspect ratio is large.The strength improves when the aspect ratio is large.

Typical fiber diameters are from 10Typical fiber diameters are from 10 QQm to 150m to 150 QQm.m.

Fibers often fracture because of surface imperfections. MakingFibers often fracture because of surface imperfections. Making

the diameter small reduces its surface area, which has fewerthe diameter small reduces its surface area, which has fewerflaws.flaws.

Long fibers are preferred because the ends of the fiber carry lessLong fibers are preferred because the ends of the fiber carry less

of the load. Thus the longer the fiber, the fewer the ends and theof the load. Thus the longer the fiber, the fewer the ends and the

higher the load carrying capacity of the fibers.higher the load carrying capacity of the fibers.


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FIBER ORIENTATIONFIBER ORIENTATION

--Maximum strength isMaximum strength is

obtained when long fibers areobtained when long fibers are

oriented parallel to theoriented parallel to the

applied loadapplied load

--The effect of fiber orientationThe effect of fiber orientation

and strength can be seen inand strength can be seen in

the plotthe plot


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--The properties of fiberThe properties of fiber

composites can becomposites can be

tailored to meet differenttailored to meet differentloading requirementsloading requirements

--By using combinations ofBy using combinations of

different fiber orientationdifferent fiber orientation

quasiquasi--isotropic materialsisotropic materials

may be producedmay be produced

Figure (a) shows a unidirectional arrangement

Figure (b) shows a quasi-isotropic arrangement


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--A three dimensionalA three dimensional

weave is also possibleweave is also possible

--This could be foundThis could be found

when fabrics are knittedwhen fabrics are knitted

or weaved togetheror weaved together


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B. Particle CompositesB. Particle Composites ParticlesParticles usuallyusually reinforcereinforce aa compositecomposite equallyequally inin allall directionsdirections

(called(called isotropicisotropic)).. PlasticsPlastics,, cermetscermets andand metalsmetals areare examplesexamples ofofparticlesparticles..

TheThe volumevolume ofof thesethese particlesparticles usuallyusually 2525 --5050%% ofof thethe volumevolume

ParticlesParticles used to strengthen a matrix do not do so in the sameused to strengthen a matrix do not do so in the same

way as fibers. For one thing, particles are not directional likeway as fibers. For one thing, particles are not directional like

fibers. Spread at random through out a matrix, particles tend tofibers. Spread at random through out a matrix, particles tend toreinforce in all directions equally.reinforce in all directions equally.

Cermets

(1) OxideBased cermets

(e.g. Combination of Al2O3 with Cr)

(2) CarbideBased Cermets(e.g. Tungstencarbide, titaniumcarbide)

Metalplastic particle composites

(e.g. Aluminum, iron & steel, copper particles)

Metalinmetal Particle Composites andDispersion Hardened Alloys

(e.g. Ceramicoxide particles)


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Structural CompositesStructural Composites Laminar compositesLaminar composites

22--d sheets or panelsd sheets or panels

Stacked and bound with orientation inStacked and bound with orientation in

altering directionsaltering directions

Improved strength in 2 or moreImproved strength in 2 or more

directions in 2d, but not 3d.directions in 2d, but not 3d.

SandwichSandwich PanelsPanels

Face sheets with uniform strength areFace sheets with uniform strength are

separated by a core or honeycomb.separated by a core or honeycomb.

honeycomb

adhesive layerface sheet


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Hybrid compositesHybrid composites

It consist of two or more types of fibersIt consist of two or more types of fibersembedded in a common matrix.embedded in a common matrix.

They provide dimensional stability, less weightThey provide dimensional stability, less weight

and improve fatigue and fracture resistance.and improve fatigue and fracture resistance.

These are used for sporting goods and lightThese are used for sporting goods and lightweight orthopedic components.weight orthopedic components.

The most common hybrid composites areThe most common hybrid composites are

carboncarbon--aramidaramid reinforced epoxy (whichreinforced epoxy (which

combines strength and impact resistance) andcombines strength and impact resistance) and

glassglass--carbon reinforced epoxy (which gives acarbon reinforced epoxy (which gives a

strong material at a reasonable price).strong material at a reasonable price).


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COMMERCIALLY AVAILABLECOMMERCIALLY AVAILABLE

FORMS OF REINFORCEMENTFORMS OF REINFORCEMENT

Random mat and woven fabric

(glass fibers)


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COMMERCIALLY AVAILABLECOMMERCIALLY AVAILABLE

FORMS OF REINFORCEMENTFORMS OF REINFORCEMENT

Carbon fiber woven fabric

glass-carbon reinforced epoxy


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MANUFACTURING OFMANUFACTURING OF

COMPOSITESCOMPOSITESHand LayHand Lay--Up/SprayUp/Spray--UpUp

--Oldest and most commonly used manufacturing methodOldest and most commonly used manufacturing method

--Usually used to produce polyester or epoxy resin parts such as boatUsually used to produce polyester or epoxy resin parts such as boat

hulls, tanks and vessels, pickhulls, tanks and vessels, pick--up truck canopiesup truck canopies--The method is quite simple, the resin and reinforcement is placedThe method is quite simple, the resin and reinforcement is placed

against the surface of an open (one sided) mold and allowed to cure oragainst the surface of an open (one sided) mold and allowed to cure or

in the case of sprayin the case of spray--up the resin/reinforcement is sprayed onto theup the resin/reinforcement is sprayed onto the

mold with a spray gunmold with a spray gun

--Often a gel coat is applied to the mold prior toOften a gel coat is applied to the mold prior toproduce a better surface quality and protect theproduce a better surface quality and protect the

composite from the elementscomposite from the elements

--A gel coat is a resin usually 0.4 to 0.7 mmA gel coat is a resin usually 0.4 to 0.7 mm

thick, commonly seen on the outer surface ofthick, commonly seen on the outer surface of

smaller boatssmaller boats


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Continuous protrusion processContinuous protrusion process

Continuous protrusionContinuous protrusion: Continuous strand fibers: Continuous strand fibers

are impregnated in resin bath, fed intoare impregnated in resin bath, fed into heatedheated

diedie andand drawn.drawn.

Used to produce beams,Used to produce beams, channels,andchannels,and pipes.pipes.


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COMPOSITESCOMPOSITESFilament WindingFilament Winding


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TheThe fibresfibres are fed through a resin bath andare fed through a resin bath and

the feeding mechanism traverses thethe feeding mechanism traverses thelength of the mandrel.length of the mandrel.

The layers ofThe layers of fibrefibre are applied to form theare applied to form the

required thickness of the laminate. Therequired thickness of the laminate. The

mandrel rotating speed and the traversingmandrel rotating speed and the traversing

speed dictate thespeed dictate the fibrefibre winding angle.winding angle.

The cure process is generally initiatedThe cure process is generally initiated

once the winding is complete either byonce the winding is complete either byheating the mandrel while it is still on theheating the mandrel while it is still on the

machine or by removing it and placing themachine or by removing it and placing the

part in an oven.part in an oven.


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COMPOSITESCOMPOSITESFilament WindingFilament Winding


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COMPOSITESCOMPOSITESResin Transfer MoldingResin Transfer Molding

--Resin transfer molding is a manufacturing method that isResin transfer molding is a manufacturing method that is

quite similar to injection molding where plastic is injectedquite similar to injection molding where plastic is injectedinto a closed moldinto a closed mold

--In the RTM process the preform (precut piece(s) ofIn the RTM process the preform (precut piece(s) of

reinforcement) is placed in the mold, the mold is closedreinforcement) is placed in the mold, the mold is closed

and the thermoset plastic matrix is injected into the mold,and the thermoset plastic matrix is injected into the mold,once the matrix is cured the part is ejectedonce the matrix is cured the part is ejected


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COMPOSITESCOMPOSITESResin Transfer MoldingResin Transfer Molding


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VacuumVacuum--Bag MoldingBag Molding PrePre--impregnated fiber is applied to the mould either by hand orimpregnated fiber is applied to the mould either by hand or

machine.machine.

The fiber area is covered with a rubber or plastic bag and the airThe fiber area is covered with a rubber or plastic bag and the air

removed using a vacuum pump.removed using a vacuum pump.

Further pressure and increased temperature are applied by placingFurther pressure and increased temperature are applied by placing

the mould in an oven or autoclave and the resin is cured.the mould in an oven or autoclave and the resin is cured. Under the applied pressure, the layers ofUnder the applied pressure, the layers of prepregprepreg are fused togetherare fused together

and any excess resin removed. The vacuum allows for voids to beand any excess resin removed. The vacuum allows for voids to be

collapsed producing a laminate with a very low void content.collapsed producing a laminate with a very low void content.

The release mechanism consists of a special film applied to eachThe release mechanism consists of a special film applied to each

surface which allows air and excess resin to pass through it.surface which allows air and excess resin to pass through it. The main advantage of this manufacturing method is that componentsThe main advantage of this manufacturing method is that components

of high quality with excellent properties can be produced. This is stillof high quality with excellent properties can be produced. This is still

thethe favouredfavoured method of the aerospace industry.method of the aerospace industry.


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