c5 Composite Materials

8/8/2019 c5 Composite Materials

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COMPOSITECOMPOSITE

MATERIALSMATERIALS


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ISSUES TO ADDRESS

What are the classes and types ofcomposites?

Why are composites used instead ofmetals, ceramics, or polymers?

What are some typical applications?


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2

Composites:

The combination of two or more materials in order

to create a new material, the properties of which

will better suited to a specific application

Matrix:

--The continuous phase

--Purpose is to:

transfer stress to other phasesprotect phases from environment

--Classification: MMC, CMC, PMC

metal ceramic polymer

woven

fibers

crosssectionview

0.5mm

0.5mm

Reprinted with permission fromD. Hull and T.W. Clyne, AnIntroduction to CompositeMaterials, 2nd ed., Cambridge

University Press, New York, 1996,Fig. 3.6, p. 47.

TERMINOLOGY/CLASSIFICATIONTERMINOLOGY/CLASSIFICATION

Dispersed phase:--Purpose: enhance matrix properties.--Classification: Particle, fiber, structural


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Composites

Combine materials with the objective ofgetting a more desirable combination ofproperties

Ex: get flexibility & weight of a polymer plus thestrength of a ceramic

Principle of combined action

Mixture gives averaged properties


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COMPOSITES

Particlereinforced

Fiberreinforced

Structural

LargeParticle

Dispersionstrengthened

Continuous(aligned)

Discontinuous(short)

LaminatesSandwich

panels

AlignedRandomlyoriented


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Particle-reinforced composites 2 subclassifications;

LARGE: the particle-matrix interactions cannot be treated onthe atomic/molecular level. Ex: concrete

DISPERSION-STRENGTHENED : particles are normally much

smaller; between 10 to 100 nm. Ex: thoria-dispersed nickel Particles used for reinforcing:

ceramics and glasses such as small mineral particles,

metal particles such as aluminum

amorphous materials, including polymers and carbon black.

Particles are used

to increase the modulus of the matrix,

to decrease the permeability of the matrix,

to decrease the ductility of the matrix

to produce inexpensive composites.


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Particle-reinforced

Examples:

-Sp eroidite

steel

matrix:ferrite (E)

(d ctile)

particles:cementite( e3 )

( rittle)

- / o

cemented

car ide

matrix:co alt(d ctile)

particles:

( rittle,ard)

- tomo ile

tires

matrix:r er(compliant)

particles:

(stiffer)

Qm

Vm:

- ol%! Qm

Qm

dapted from ig ,

allister e ( ig iscopyrig t UnitedStates Steel

orporation, 9 )

dapted from ig 4,

allister e ( ig 4 isco rtesy

ar oloySystems,Department,

General Electricompany )

dapted from ig

,

allister e ( ig

isco rtesy GoodyearTire and R er

ompany )

COMPOSITE SURVEY: Particle-I

Fi er-reinforced tructural


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Composite Survey: Particle-II

Concrete gravel + sand + cement- Why sand andgravel? Sand packs into gravel voids

Reinforced concrete - Reinforce with steel rerod or remesh- increases strength - even if cement matrix is cracked

Prestressed concrete - remesh under tension during setting ofconcrete. Tension release puts concrete under compressive force

- Concrete much stronger under compression.

- Applied tension must exceed compressive force

Particle-reinforced Fiber-reinforced Structural

threaded

rod

nut

Post tensioning tighten nuts to put under tension


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Examples:

an automobile tire which has carbon blackparticles in a matrix of polyisobutyleneelastomeric polymer.

spheroidized steel where cementite istransformed into a spherical shape whichimproves the machinability of the material.

concrete where the aggregates ( sand and gravel)are the particles and cement is the matrix


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Fiber-reinforced composites Reinforcing fibers can be made of metals, ceramics, glasses or

polymers

Fibers increase the modulus of the matrix material.

Fibers are difficult to process into composites which makes fiber-

reinforced composites relatively expensive. Examples:

sports equipment, such as a time-trial racing bicycle framewhich consists of carbon fibers in a thermoset polymer matrix.

Body parts of race cars and some automobiles are compositesmade of glass fibers (or fiberglass) in a thermoset matrix.

The strength and other properties of fiber-reinforced compositesare influence by

the arrangement or orientation of the fibers relative to oneanother

the fiber concentration


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Composite Survey: Fiber-I

Fibers very strong

Provide significant strength improvement tomaterial

Ex: fiber-glass Continuous glass filaments in a polymer matrix

Strength due to fibers

Polymer simply holds them in place



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Composite Survey: Fiber-II

Fiber Materials Whiskers - Thin single crystals - large length to

diameter ratio

graphite, SiN, SiC

high crystal perfection extremely strong, strongestknown

very expensive


Fibers

polycrystalline or amorphous

generally polymers or ceramics

Ex: Al2O3 , Aramid, E-glass, Boron, UHMWPE

Wires

Metal steel, Mo, W


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Aligned Continuous fi ersFi er-reinforced

rticle-reinforced tructur l

Ex mples:

From W Funk nd E Bl nk, Creepdeform tion of Ni3Al-Mo in-situcomposites", Met ll Tr ns A

ol 19(4),pp 987-998, 1988 Used

ith

permission

fr cturesurf ce

m trix: E(Mo) (ductile)

fi ers:K (Ni3Al) ( rittle)

Qm

--Met l: K'(Ni3Al)-E(Mo)

y eutectic solidific tion

--Gl ss / iC fi ersformed y gl ss slurry

Egl ss = 76G ; E iC = 4 G

From F L M tthe

s nd R L R

lings, Composite M teri ls;Engineering nd cience, Reprinted

, CRC

ress, Boc

R

ton, FL,

( ) Fig 4 , p 145 (photo y D vies); ( ) Fig 11

, p 349 (microgr ph y H Kim, Rodgers, nd R D R

lings) Used

ith permission of CRC ress, Boc R ton, FL

( )

( )

COMPOSITE SURVEY: Fiber-I


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Discontinuous, random 2D fi ersFi er-reinforcedartic e-reinforced tructura

Examp e: Car on-Car on--process: fi er/pitch, then

urn out at up to 2500C

--uses: disk rakes, gastur ine exhaust f aps, nose

cones

Other variations:--Discontinuous, random 3D

--Discontinuous, 1D

fi ers iein p ane

vie onto p ane

C fi ers:ver stiffver strong

C matrix:ess stiffess strong

Adapted from F! L ! Matthe " s and R ! L ! Ra" # ings, Composite Materia # s; Engineeringand

$

cience, Reprint ed ! , CRC % ress, BocaRaton, FL, 2000. (a) Fig. 4.24(a), p. 151; (

&)

Fig. 4.2( & ) p. 351. Reproduced " ithpermission of CRC % ress, Boca Raton, FL.

(b)

(a)

COMPOSITE SURVEY: Fiber-II


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Composite Production Methods-I

Pultrusion Continuous fibers pulled through resin tank, then

preforming die & oven to cure

Adapted from Fig.16.13, Callister 7e.


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Composite Production Methods-II

Filament Winding Ex: pressure tanks

Continuous filaments wound onto mandrel

Adapted from Fig. 16.15, Callister 7e. [Fig.16.15 is from N. L. Hancox, (Editor), FibreComposite Hybrid Materials, The MacmillanCompany, New York, 1981.]


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Fiber-reinforcedParticle-reinforced

9

tructural

tackedandbondedfiber-reinforced sheets-- stacking sequence: e.g., 0/90

-- benefit: balanced, in-plane stiffness

andwich panels-- lowdensity, honeycombcore

-- benefit: smallweight, largebending stiffness

Adaptedfrom

Fig. 16.16,Callister 6e.

Adaptedfrom Fig. 16.17,Callister 6e. (Fig. 16.17 isfrom Engineered Materials

Handbook,'

ol. 1, Composites, A(

M International, Materials Park, OH, 1987.

COMPOSITE SURVEY: Structural

honeycomb

adhesivelayerface sheet


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Structural composites

Common structural composite types are:

Laminar:

Is composed of two-dimensional sheets or panelsthat have a preferred high strength direction such

as is found in wood and continuous and alignedfiber-reinforced plastics.

The layers are stacked and cemented togethersuch that the orientation of the high-strengthdirection varies with each successive layer.

One example of a relatively complex structure ismodern ski and another example is plywood.


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Sandwich Panels:

Consist of two strong outer sheets which arecalled face sheets and may be made of aluminumalloys, fiber reinforced plastics, titanium alloys,

steel. Face sheets carry most of the loading and

stresses.

Core may be a honeycomb structure which hasless density than the face sheets and resists

perpendicular stresses and provides shear rigidity. Sandwich panels can be used in variety of

applications which include roofs, floors, walls ofbuildings and in aircraft, for wings, fuselage andtailplane skins.


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ADVANTANGES OF COMPOSITE

High strength to weight ratio (lowdensity high tensile strength)

High creep resistance

High tensile strength at elevatedtemperatures

High toughness

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