Phases of Composite Materials_sicakova

7/28/2019 Phases of Composite Materials_sicakova

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I. Phases of composite materials types and functions

ALENA SIKOVTECHNICAL UNIVERSITY OF KOICECIVIL ENGINEERING FACULTYDEPARTMENT OF MATERIAL ENGINEERING

LLP ERASMUS - IP 2012, PRAGUE


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Definition of the composite material

A multiphasematerial formed from a

combination of materials which differ incomposition or form, remain bonded together,

and retain their identities and properties.

Composites maintain an interface betweencomponents and act in concert to provide

improved specific or synergistic

characteristicsnot obtainable by any of the original components

acting alone


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Synergistic effect

QK = Q(A) + Q(B) + Q(C) + Q(A) . Q(B) . Q(C)sum effect synergistic effect

where: QK; Q(A); Q(B); Q(C) quality of composite / components A, B, C contain of components

Synergistic effect is one of the objectivecharacteristics differentiating the compositematerials from the other ones


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Phases of a composite material

Phaseis:

a region ofmatter thatpossesses uniform

intensivepropertiesthroughout itsvolume

a homogeneousarea of compositematerial

Discontinuous phase (stiffer andstronger) - filler/reinforcement,

Continuous phase (less stiff andweaker) - binder/matrix

Interphase between matrix andreinforcement


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surrounds and supports otherconstituents by keepingtheirrelative positions and holding themtogether,

protectsboth the reinforcementand whole the composite fromenvironment effects/deterioration;

transfersthe loading toreinforcement

protectsthe filler from abrasion (witheach other)

enhancessome of the properties ofthe resulting material (that filler aloneis not able to impart). Theseproperties are such as: transverse strength of a lamina impact resistance

providesbetter finish to final product

imparts special properties,such as electrical andmechanical, to improve thematrix properties,

provides some stiffeningandstrenghteningof the material,

provides control of cracksriseand development

MatrixMatrix FillerFiller

Roles of phases


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Systems of composite materials based

on ratio of individual phases

matrix

1st limiting system

Vc = Vm

matrixfiller

Composite of I. type

Vc = Vm + VfFiller is dispersed

Vfcan increase at the cost of Vm

up to maximal possible fillig of volume

2 nd limiting system

Vc = Vm + VfClosest packing of volume by filler


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Composite of II. type

Vc= V

f+ V

m+ V

v

Changing the ratio of phases ispossible only by reduction of matrixand incorporation of voids instead

Discrete voids

Composite of III. type

Vc = Vf+ Vm + Vv

Volume of voids increases, voids startto be continuous

3 rd limiting system

Vc = Vv + Vf

Without matrix

Composite is incoherent, loose


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Parameters influencing resulting properties of

a composite material

Volume (or weight) fraction of phases Shape, geometry, and distribution of the phases Orientation of filler/reinforcement in system

(isothropy/anisothropy) Individual properties of phases, compatibility of

components Bonding strength/ITZ (interfacial transition zone)

properties on the interface between the dispersed phaseand matrix

Interaction of composite and ambient environment Age of composite components Production technology


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Filler/reinforcement

Forms: Particles Flakes Fibers


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Filler/reinforcement - Orientation Isotropic

Having uniform properties in

all directions. The measuredproperties of an isotropicmaterial are independent ofthe axis of testing.

AnisotropicNot isotropic; having

mechanical and/or physicalproperties which vary withdirection relative to naturalreference axes inherent inthe material


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Classification of composite materialsbased on the form and orientation of

filler/reinforcement


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Filler/reinforcement - Particles

They usually reinforce a composite equally in all

directions. Particle fillers are usually of very small dimension(0,01 0,1 m) and they occupy app. 15% ofcomposite volume they are dispersed without mutualconnection

Typical particles in the terms of constructioncomposite materials are of bigger dimensions(granularity), such as sand and gravel


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Usual materials of particle fillers Natural rocks: granit, feldspar, silica, limestone,

gypsum, kaoline ... Glass microspheres, milled glass

Metal particles Ceramic particles


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Filler/reinforcement - Fibers

Natural Fibres:

Animal fibres: Silk, Wool, Spider silk, Sinew, Camelhair Vegetable fibres: Cotton, Jute, Bamboo, Sisal, Maze,

Hemp, Sugarcane, Banana, Ramie, Kapok, Coir,

Abaca, Kenaf, Flax, Raffia palmProcessed Fibres: Mineral fibres: Asbestos, Basalt, Glass Metal fibers: steel Polymer fibers: PE, PP, PVA ...


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Advanced fibres: fibres possessing high specific

strength [/]) Glass Carbon

Organic: aramid, kevlar Ceramic: borone, silicone


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Performance properties of fibers

High tensile strength

Specific modulus of elasticity Stability in actual matrix Shape

Surface treatment End treatment/shape Lenght and diameter aspect ratio (large aspect ratios

result in stronger composites, but they are more difficultto process)


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Forms of Fibrous CompositesSingle-layered composites: continious (Layer, Lamina, Ply - any of the term is used)

unidirectional bi-directional

discontinuous

random orientation preferred orientation


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Multi-layered composites:

Laminates

Hybrides


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Kinds of fibersSteel

The usual way of application is as short fibers torandom reinforcement of concrete they are made of cold drawn steel wire with low

content of carbon various shapes and endings (hooked, undulated or

flat) are produced in order to obtain correct anchoragein concrete


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Polypropylene

They are produced in two types: as fibrillated ones(bundles of several fibers) cut from a sheet; or

monofilaments cut from a yarn

Monofilaments Fibrillated fibers


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Glass

manufactured frommolten glass, fromwhich glassmonofilaments aredrawn and thengathered to strands.The strands are usedfor preparation ofdifferent glass fiber

products (yarns,rovings, wovenfabrics, mats)


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Carbon

They are commonly produced by the pyrolysis ofhydrocarbon precursors in a non-reactive atmosphere carbon fibers offer high strength, high stiffness, low

density, and low thermal expansion not achievable withany other structural fibers.

In addition, carbon fibers have high thermal and electricalconductivity which make them suitable for specialized

applications where thermal energy and electrical currentneed to be specifically controlled


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Carbon fibers allow to produce a composites withexcellent strength and stiffness and reduced weight


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The role of fibres in cementitious materials is

that they generally have two positive effects:

reduction of shrinkage strainsin early age of

concrete, when high risk of shrinkage cracks formationcomes fibers with lower modulus of elasticityaresufficient

carrying the stressescaused by external loads fibers with higher modulus of elasticityarerequired


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Properties of selected types

TypeDiameter

[mm]

Density

[g/cm3]

Tensilestrength

[GPa]

Modulus

of

elasticity

[GPa]

Ultimateelongation

[%]

Steel 0,1 - 1,0 7,8 0,3 - 2,0 200 0,5 - 3,5

Polypropylene 0,02 - 0,4 0,9 0,3 - 0,5 5 15 - 25

Glass 0,05 - 0,15 2,5 1,0 - 3,0 70 - 80 1,5 - 4,5

Carbon 0,008 - 0,01 1,9 1,0 - 3,0 230 - 400 0,5 - 1,0


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Matrix

The primary consideration in the selection of a matrix isits basic mechanical properties. For high-performancecomposites, the most desirable mechanical propertiesof a matrix are:

High modulus of elasticity, which influences the

compressive strength of the composite High tensile strength, which controls the intraply

cracking in a composite laminate

High fracture toughness, which controls plydelamination and crack growth


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Matrix Usual materials

Plastics

Metals Ceramics


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Matrix Usual materials - Plastics

Thermoplastics:

polypropylene, polyvinyl chloride (PVC), nylon,

polyurethane, poly-ether-ether ketone (PEEK), polyphenylene sulfide (PPS),

polysulpone


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Thermoplastics are increasingly used over thermosetsbecuase of the following reasons:

Processing is faster than thermoset composites sinceno curing reaction is required. Thermoplasticcomposites require only heating, shaping and cooling.

Better properties: high toughness (delamination resistance) and

damage tolerance, low moisture absorption chemical resistance

They have low toxity Cost is high


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Thermosets:

polyesters epoxies polyimides

other resins


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Properties of selected typesEpoxy Polyester Phenolic Polyamid

Modulus of elasticity

Em (MPa)4 500 4 000 3 000

4 000 -

19000Shear modulus of

elasticity Gm

(MPa)

1 600 1 400 1 100 1 100

Tensile strengthpm (MPa)

130 80 70 70

Density

(kg.m-3)1 200 1 200 1 300 1 400

Maximaltemperature

Tmax (oC)

90 -200 60 - 100 120 - 200 250 - 300


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Matrix Usual materials - Metals

Aluminum Titanium Copper


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Matrix Usual materials - Ceramics

Carbon Silicon carbide Silicon nitride

Lime, gypsum, cement


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Phase boundary - interfacial transition zone

Thin region in which the intensive properties change

discontinuously. Usually the properties of boundaryare worseas those of separate phases. At all kinds of composites there is a critical area, with

the highest probability of cracks and failure all ofcomposite. It is the weakest area of compositematerial

Good bonding(adhesion) between matrix phase and

dispersed phase provides better transfer of load


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Character of ITZ is influenced and can beoptimized by:

physical properties of particles/fibers (specificsurface area, surface coarseness, porosity, ),

chemical processes - reaction between matrix andfiller

technological processes: mixing, compacting,forming, curing of composite

I t f i l t iti


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Interfacial transition zone

Ways of modificationIn cementitious CM1.Through aggregate quality: optimal grading (means grading with

minimal void ratio. It can be reached usingaggregates of various grain size)

surface area - minimal shape - regular surface - coarse

2. Through matrix quality:

porosity, cracks and hydratation productscontrol due to minimal water/cement ratioand additive fine-grain materials(granulated blast furnace slag, fly ash,microsilica)


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Role of mineral fine-grain materials:

improvement in packing, that is, action as a filler withmuch more smaller particles than cement particles

better adhesion of matrix

aggregate


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In polymer CM:

aggregate must be of good quality, free of dust andother debris, and dry.

failure of these criteria can reduce the bond strengthbetween the polymer binder and the aggregate. bonding can be improved by some special chemical

admixtures


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LITERATURE: LEE, S. M. Preface to the Dictionary of Composite Materials Technology.

http://composite.about.com/od/referencematerials/l/blpreface.htm MORVA, T. Composite Building Materials. http://ezinearticles.com/?Composite-Building-

Materials&id=353965 CAMPBELL, F.C. Structural Composite Materials. Chap. 1: Introduction to Composite Materials.

2010. http://www.asminternational.org/content/ASM/StoreFiles/05287G_Sample_Chapter.pdf http://www.ewp.rpi.edu/hartford/~taurim/EP/Report%20Material/Resources/frc_chap_2.pdf ISHAI, O. Engineering Mechanics of Composite Materials.

http://www.globalspec.com/reference/60655/203279/chapter-1-introduction BARE, R. Composite materials. In Czech. SNTL. Praha 1988.

AGARWAL, B., BROUTMAN, L. Fiber composites. In Czech. SNTL. Praha 1987 KOPELIOVICH, D. Structure of Composites.

http://www.substech.com/dokuwiki/doku.php?id=structure_of_composites&DokuWiki=9cf99564549611b3ac3e32e5e472e368

LA, V.: Mechanika kompozitnch materil, 2006. In:http://www.kme.zcu.cz/download/predmety/mkm/1-uvod.ppt

SCRIVENER, K. at al. he Interfacial Transition Zone (ITZ) Between Cement Paste and Aggregate inConcrete. In Chemistry and Materials Science. Interface Science. Vol. 12, N. 4, 411-421, DOI:10.1023/B:INTS.0000042339.92990.4c

TREFIL, V. Influence of microsilica and nanosilica on the hardened concrete properties. In Czech.http://www.stavebnitechnologie.cz/view.php?cisloclanku=2002032802

What are composites?http://www.composites.ugent.be/home_made_composites/what_are_composites.html

MOHITE, PM: Composite Materials. In: http://home.iitk.ac.in/~mohite/Composite_introduction.pdf

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Phases of Composite Materials_sicakova