ch16_composie material

7/26/2019 ch16_composie material

1/23

Chapter 16 - 1

ISSUES TO ADDRESS...

What are the classes and types of composites?

What are the advantages of using compositematerials?

How do we predict the stiffness and strength of the

various types of composites?

Chapter 16: Composite Materials


2/23

Chapter 16 - 2

Composite

Combination of two or more individualmaterials

esign goal! obtain a more desirablecombination of properties "principle of

combined action#

$ e%g%& low density and high strength


3/23

Chapter 16 - '

Composite!

-- (ultiphase material that is artificiallymade%

)hase types! -- (atri* - is continuous

-- ispersed - is discontinuous andsurrounded by matri*

Terminology/Classii!ation

+dapted from ,ig% 16%1"a#&

Callister & Rethwisch 9e%


4/23

Chapter 16 -

ispersed phase! -- )urpose!

((C! increase y& TS& creep resist%

C(C! increase K.c

)(C! increase E& y& TS& creep resist%

-- /ypes! particle& fiber& structural

(atri* phase! -- )urposes are to! - transfer stress to dispersed phase

- protect dispersed phase from

environment

-- /ypes! ((C& C(C& )(C

metal ceramic polymer

Terminology/Classii!ation

0eprinted with permission from

% Hull and /%W% Clyne&An

Introduction to Composite Materials&

2nd ed%& Cambridge niversity )ress&

ew 3or4& 1556& ,ig% '%6& p% %

woven

fibers

crosssectionview

7%8mm

7%8mm


5/23

Chapter 16 - 8

Classii!ation o Composites

Large-

particle

Dispersion-

strengthened

Particle-reinforced

Continuous

(aligned)

Aligned Randomly

oriented

Discontinuous

(short)

Fiber-reinforced

Laminates Sandwich

panels

Structural

Composites

+dapted from ,ig% 16%2&

Callister & Rethwisch 9e%


6/23

Chapter 16 - 6

Classii!ation: "arti!le#Reinor!e$ %i&

9*amples!

,ig% 1%12& Callister &

Rethwisch 9e%"Copyright 151 by nited

:tates :teel Corporation%#

- :pheroidite

steel

matri*!ferrite "#

"ductile#

particles!cementite",e

'C#

"brittle#

67;m

,ig% 16%& Callister &

Rethwisch 9e%"Courtesy of Carboloy

:ystems epartment&


7/23Chapter 16 -

Classii!ation: "arti!le#Reinor!e$ %ii&

Concrete$ gravel > sand > cement > water - Why sand andgravel? :and fills voids between gravel particles

0einforced concrete $ 0einforce with steel rebar or remesh

- increases strength - even if cement matri* is crac4ed

)restressed concrete - 0ebar=remesh placed under tension during setting of concrete

- 0elease of tension after setting places concrete in a state of compression

- /o fracture concrete& applied tensile stress must e*ceed this

compressive stress

)article-reinforced ,iber-reinforced :tructural

threaded

rod

nut

)osttensioning$ tighten nuts to place concrete under compression


8/23Chapter 16 -

9lastic modulus& Ec& of composites!

-- two @rule of mi*tureA e*tremes!

+pplication to other properties!

-- 9lectrical conductivity& e! 0eplace EBs in euations with eBs%

-- /hermal conductivity& k! 0eplace EBs in euations with kBs%

,ig% 16%'& Callister &

Rethwisch 9e%"0eprinted with permission

from 0% H% Droc4&ASTM

roceedin!s& Eol% 6'& 156'%

Copyright +:/( .nternational&

177 Farr Harbor rive& West

Conschohoc4en& )+ 152%#

Classii!ation: "arti!le#Reinor!e$ %iii&

lower limit!

1

EcG

"m

Em>

"p

Ep

upper limit! c m mE G " E > "pEp


ata!Cu matri*

w=tungsten

particles

7 27 7 67 7 177

187

277

287

'77'87

vol tungsten

E"


9/23Chapter 16 - 5

Classii!ation: 'i(er#Reinor!e$ %i&

,ibers very strong in tension

$ )rovide significant strength improvement to the

composite

$ 9*! fiber-glass - continuous glass filaments in apolymer matri*


10/23Chapter 16 - 17

Classii!ation: 'i(er#Reinor!e$ %ii&

,iber /ypes$ Whis4ers- thin single crystals - large length to diameter ratios

graphite& silicon nitride& silicon carbide

high crystal perfection $ e*tremely strong& strongest 4nown

very e*pensive and difficult to disperse


$ ,ibers

polycrystalline or amorphous

generally polymers or ceramics

9*! alumina& aramid& 9-glass& boron& H(W)9

$ Wires

metals $ steel& molybdenum& tungsten


11/23Chapter 16 - 11

'i(er Alignment

alignedcontinuous

aligned randomdiscontinuous

,ig% 16%& Callister &Rethwisch 9e%

/ransverse

direction

Iongitudinal

direction


12/23Chapter 16 - 12

+ligned Continuousfibers 9*amples!

,rom W% ,un4 and 9% Flan4& @Creep

deformation of i'+l-(o in-situ

compositesJ& Metall# Trans# AEol% 15"#& pp%

5-55& 15% sed with permission%

-- (etal! B"i'+l#-$"(o#

by eutectic solidification%

Classii!ation: 'i(er#Reinor!e$ %iii&


matri*! $"(o# "ductile#

fibers! B"i'+l# "brittle#

2;m

-- Ceramic!


13/23

Chapter 16 - 1'

iscontinuous fibers& random in 2 dimensions 9*ample! Carbon-Carbon -- fabrication process!

- carbon fibers embedded

in polymer resin matri*&

- polymer resin pyrolyLed

at up to 2877MC%

-- uses! dis4 bra4es& gas

turbine e*haust flaps&

missile nose cones%

Nther possibilities! -- iscontinuous& random '

-- iscontinuous& aligned

+dapted from ,%I% (atthews and 0%I% 0awlings&

Composite Materials% En!ineerin! and Science&

0eprint ed%& C0C )ress& Foca 0aton& ,I& 2777%

"a# ,ig% %2"a#& p% 181K "b# ,ig% %2"b# p% 181%

"Courtesy .%O% avies# 0eproduced with

permission of C0C )ress& Foca 0aton& ,I%

Classii!ation: 'i(er#Reinor!e$ %i)&


"b#

fibers liein plane

view onto plane

C fibers!very stiffvery strong

C matri*!less stiffless strong

"a#

877 ;m


14/23

Chapter 16 - 1

Critical fiber length for effective stiffening P strengthening!

9*! ,or fiberglass& common fiber length Q 18 mm needed

Classii!ation: 'i(er#Reinor!e$ %)&


fiber diameter

shear strength of

fiber-matri* interface

fiber ultimate tensile strength

,or longer fibers& stress transference from matri* is more efficient:hort& thic4 fibers! Iong& thin fibers!

Iow fiber efficiency High fiber efficiency


15/23

Chapter 16 - 18

Composite Stiness:

*ongit+$inal *oa$ing

Continuous fibers- 9stimate fiber-reinforced compositemodulus of elasticity for continuous fibers

Iongitudinal deformation

cG m"m

> &"& and ec

G em

G e&

volume fraction isostrain

EclG Em"m> E " EclG longitudinal modulus

c ' composite

G fibermG matri*


16/23

Chapter 16 - 16

Composite Stiness:

Trans)erse *oa$ing

.n transverse loading the fibers carry less of the load

ecG em"m

> e&"& and c

G m

G &

G

f

f

m

m

ctE

V

E

V

E+=

EctG transverse modulus

c ' composite

G fibermG matri*

isostress

Ect=

EmE

f

VmEf+VfEm


17/23

Chapter 16 - 1

9stimate of Ecdfor discontinuous fibers!

-- valid when fiber length R

-- 9lastic modulus in fiber direction!

efficiency factor!-- aligned! KG 1 "aligned parallel#

-- aligned! KG 7 "aligned perpendicular#

-- random 2! KG '= "2 isotropy#

-- random '! KG 1=8 "' isotropy#

/able 16%'& Callister & Rethwisch 9e%":ource is H% Drenchel& (i)re Reinorcement&

Copenhagen! +4ademis4 ,orlag& 156%#

Composite Stiness


EcdG Em"m> KE"


18/23

Chapter 16 - 1

Composite Strength


9stimate of for discontinuous fibers!cd"

2% When lR lc

l

1% When lQ lc

l

l


19/23

Chapter 16 - 15

Composite "ro$+!tion Metho$s %i&

,ig% 16%1'& Callister & Rethwisch 9e%

)ultrusion Continuous fibers pulled through resin tan4 to impregnate fibers with

thermosetting resin .mpregnated fibers pass through steel die that preforms to the desired shape )reformed stoc4 passes through a curing die that is

$ precision machined to impart final shape$ heated to initiate curing of the resin matri*


20/23

Chapter 16 - 27

Composite "ro$+!tion Metho$s %ii&

,ilament Winding$ Continuous reinforcing fibers are accurately positioned in a predetermined

pattern to form a hollow "usually cylindrical# shape$ ,ibers are fed through a resin bath to impregnate with thermosetting resin$ .mpregnated fibers are continuously wound "typically automatically# onto a

mandrel$ +fter appropriate number of layers added& curing is carried out either in an

oven or at room temperature

$ /he mandrel is removed to give the final product

,ig% 16%18& Callister & Rethwisch 9e%S,rom % I% Hanco*& "9ditor#& (i)re Composite *y)rid

Materials& /he (acmillan Company& ew 3or4& 151%T


21/23

Chapter 16 - 21

Iaminates-

-- stac4ed and bonded fiber-reinforced sheets

- stac4ing seuence! e%g%& 7U=57U

- benefit! balanced in-plane stiffness+dapted from

,ig% 16%16&

Callister &

Rethwisch +e%

Classii!ation:Str+!t+ral


:andwich panels -- honeycomb core between two facing sheets

- benefits! low density& large bending stiffness

honeycombadhesive layer

face sheet

,ig% 16%1& Callister & Rethwisch 9e%"0eprinted with permission from En!ineered

Materials *and)ook& Eol% 1& Composites&

+:( .nternational& (aterials )ar4& NH& 15%#


22/23

Chapter 16 - 22

Composite ,eneits

)(Cs! .ncreased E=

E"


23/23

Chapter 16 - 2'

Composites types are designated by!

-- the matri* material "C(C& ((C& )(C# -- the reinforcement "particles& fibers& structural#

Composite property benefits! -- ((C! enhanced E& & creep performance

-- C(C! enhanced KIc

-- )(C! enhanced E-,& y& TS-, )articulate-reinforced! -- /ypes! large-particle and dispersion-strengthened

-- )roperties are isotropic

,iber-reinforced!

-- /ypes! continuous "aligned# discontinuous "aligned or random#

-- )roperties can be isotropic or anisotropic

:tructural! -- Iaminates and sandwich panels

S+mmary

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ch16_composie material