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Ing. Blanka Tomkov, Ph.D.Ing. Blanka Tomkov, Ph.D. Department of Textile MaterialsDepartment of Textile Materials

3. Textile Composites3. Textile Composites

Composite PropertiesComposite Properties

MajorMajoreffectseffects


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Effects influencing composite propertiesEffects influencing composite properties

Properties of componentsProperties of components

mechanicalmechanical,, thermalthermal,, electricalelectrical etcetc..

GeometryGeometry andand distributiondistribution ofofcomponentscomponents

includingincluding porespores VolumeVolume fraction of componentsfraction of components

Properties ofProperties ofinterface (interface (adhesionadhesion)) interaction of componentsinteraction of components


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Ing. Blanka Tomkov, Ph.D.Ing. Blanka Tomkov, Ph.D. Department of Textile MaterialsDepartment of Textile Materials33


Properties of componentsProperties of components


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Selected properties of main fibrousSelected properties of main fibrousreinforcementsreinforcements


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Selected properties of main matricesSelected properties of main matrices

MostMost usefuluseful composition of componentscomposition of components

Highest efficiency ofHighest efficiency of SYNERGIC EFFECTSYNERGIC EFFECT




The shape of dispersed componentThe shape of dispersed component It is chosen dueIt is chosen due toto the function of componentthe function of component

Composite reinforcementComposite reinforcement

short fibres made from low cost materialsshort fibres made from low cost materials

technology similar totechnology similar to standard plastic technologiesstandard plastic technologies

the load is transfered between fibres and matrixthe load is transfered between fibres and matrix

throughthrough fibresfibres surfacessurfaces

through fibres endsthrough fibres ends

continuous fibrescontinuous fibres

highest reinforcing effecthighest reinforcing effect

the load is transferred mainly through the fibresthe load is transferred mainly through the fibres clip effectclip effect

tensile strength of fibres is influenced by their lengthtensile strength of fibres is influenced by their length

longer fibreslonger fibres lowerlowertensile strengthtensile strength

strength is also influencedstrength is also influenced byby moisture and temperaturemoisture and temperature




GeometryGeometry of one continuous phase systemof one continuous phase system

GeometryGeometry characteristicscharacteristics

size and distribution of particlessize and distribution of particles

shape of particlesshape of particles

System characteristicsSystem characteristics

concentrationconcentration(volume(volume fractionfraction ofofparticles)particles)

concentration distribution of particlesconcentration distribution of particles

((range ofrange ofphasesphases mixturemixture)) Different concentration distributionsDifferent concentration distributions --same concentrationsame concentration

orientation of particlesorientation of particles topology of particlestopology of particles

interaction of particlesinteraction of particles

C




GeometryGeometry limits for componentlimits for component volumevolume fractionsfractions

Example: VolumeExample: Volume fraction of spheresfraction of spheres -- the same diameter,the same diameter,various formationvarious formation

Simple cubic 52 %Simple cubic 52 %

BodyBody--centered cubic 60 %centered cubic 60 %

FaceFace--centered cubic 74 %centered cubic 74 %

Random formation of spheresRandom formation of spheres volume ratiovolume ratio 6060 63 %63 %

Random formation of spheresRandom formation of spheres

with various diameterswith various diameters

volume ratiovolume ratio 8585 90 %90 %

3 T til C it3 T til C it


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Properties of fiberProperties of fiber--matrixmatrix interfaceinterface

3 T til C it3 T til C it




FiberFiber--MatrixMatrix interfaceinterface

NanoNano--sized boundary between fibres and matrixsized boundary between fibres and matrix

interfaceinterface boundary between any twoboundary between any two phasesphases

dropdrop changechange ofofchemicalchemical andand

physical propertiesphysical properties

resultresult ofoftwo surfacestwo surfaces interaction,interaction,

thatthat dependsdepends onon thethe surface structuresurface structure

and propertiesand properties of both phasesof both phases thethe structurestructure andand propertiesproperties ofofinterfaceinterface differdifferfromfrom bothboth

phasesphases

3 T til C it3 Textile Composites




Each systemEach system possesspossess specificspecific interfaceinterface IdealIdeal interfaceinterface

infinitelyinfinitely

thinthin

,,

tighttight

,,

nono defectsdefects

RealReal interfaceinterface

complicated chemical andcomplicated chemical and physical structurephysical structure

Important influenceImportant influence onon composite propertiescomposite properties

e.g.e.g.

fracture toughnessfracture toughness

corrosive behaviourcorrosive behaviour

3 Textile Composites3 Textile Composites




InIn compositescomposites areare importantimportant

TheThe structure ofstructure ofinterfaceinterface

what itwhat it is made from andis made from and howhow??

Physical properties ofPhysical properties ofinterfaceinterface mechanicalmechanical

great difference between mechanical properties of fibres andgreat difference between mechanical properties of fibres andmatricesmatrices

thethe tensiontension isis transferredtransferred from matrix tofrom matrix to fibresfibres through thethrough theinterfaceinterface

other important propertiesother important properties

elektricalelektrical

opticaloptical

thermalthermal



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Impact of joining components on interfaceImpact of joining components on interface

propertiesproperties Various layersVarious layers

different propertiesdifferent properties

no chemical bonds, no physical joiningno chemical bonds, no physical joining

no tensile strength of compositeno tensile strength of composite

inin--plane modulus depends on the specimen clampingplane modulus depends on the specimen clamping

All layers tightly fixed in jawAll layers tightly fixed in jaw

CLIP EFFECTCLIP EFFECT all layer carry tensionall layer carry tension

Strength and stiffness of compositeStrength and stiffness of composite

fibres are bonded by matrixfibres are bonded by matrix



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Composites with weak interfaceComposites with weak interface

lower strength and stiffnesslower strength and stiffness

more flexiblemore flexible

Composites with strong interfaceComposites with strong interface high strength and stiffnesshigh strength and stiffness

hard, brittlehard, brittle

Character of joining between fibres and matrixCharacter of joining between fibres and matrix

atomic distributionatomic distribution

chemical properties of fibreschemical properties of fibres conformation and chemical properties of matricesconformation and chemical properties of matrices

Strength of joinings is affected byStrength of joinings is affected byADHESIONADHESION



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Mechanisms of adhesionMechanisms of adhesion

Five main mechanismsFive main mechanisms

joining between fibres and matricesjoining between fibres and matrices

they work either separately or in conjunctionthey work either separately or in conjunction

Adsorption and wettingAdsorption and wetting

InterdiffusionInterdiffusion

Electrostatic attractionElectrostatic attraction

Chemical bondChemical bond

Mechanical adhesionMechanical adhesion



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Adsorption and wettingAdsorption and wetting

AdsorptionAdsorption Adsorption is the accumulation ofAdsorption is the accumulation ofatomsatoms orormoleculesmolecules on the surface of materialon the surface of material

This process creates a film of theThis process creates a film of the adsorbateadsorbate (the molecules or atoms being(the molecules or atoms beingaccumulated) on the adsorbent's surfaceaccumulated) on the adsorbent's surface

WettingWetting

-- contact anglecontact angle

SGSG == SLSL ++ LGLG.cos.cos

= 0 = 0

spontaneous wettingspontaneous wetting

= 180 = 180

no wettingno wetting

Wetting of real surface:Wetting of real surface:

TwoTwo electrically neutral, hard, roughelectrically neutral, hard, rough

surfacessurfaces also roughnesses in microscopic scalealso roughnesses in microscopic scale

contamination by oxides, dust particlescontamination by oxides, dust particles

etc.etc.

contact points onlycontact points only

Improvement of wettingImprovement of wetting

cleaning and smoothing of surfacecleaning and smoothing of surface

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InterdiffusionInterdiffusion

strength of joining is influenced bystrength of joining is influenced by number of diffusive moleculesnumber of diffusive molecules

conformation of moleculesconformation of molecules

molecular movementmolecular movement entanglementsentanglements

Electrostatic attractionElectrostatic attraction

two oppositely charged surfacestwo oppositely charged surfaces

interaction of acid and baseinteraction of acid and base

oppositely charged ionsoppositely charged ions

positively charged groups on molecular ends are attracted bypositively charged groups on molecular ends are attracted by

anions rised from polymer orientationanions rised from polymer orientation

strength of interface depends on charge densitystrength of interface depends on charge density

it is not wetit is not wet--stablestable



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Chemical bondChemical bond

chemical groups on fiber surfacechemical groups on fiber surface

+ compatible chemical group of matrix+ compatible chemical group of matrix

Mechanical adhesionMechanical adhesion Two surfaces are just mechanically stuckedTwo surfaces are just mechanically stucked

high shear strengthhigh shear strength

depends on size of irregularitiesdepends on size of irregularities

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