01 Introduksi Material Komposit

8/20/2019 01 Introduksi Material Komposit

1/45

MMF410803 Material

Komposit (2sks)

Prof. Dr. Ir. Anne Zulfia MSc


2/45

Pengenalan

Komposit SecaraUmum


3/45

The world of materials

PE, PP, PCPA (Nylon)

Polymers,elastomers

Butyl rubberNeoprene

Polymer foamsMetal foams

FoamsCeramic foams

Glass foams

Woods

Naturalmaterials

Natural fibres:Hemp, Flax,

Cotton

GFRPCFRP

CompositesKFRP

Plywood

Alumina

Si-Carbide

Ceramics,glasses

Soda-glassPyrex

SteelsCast ironsAl-alloys

MetalsCu-alloysNi-alloysTi-alloys


4/45


5/45

Pengertian Komposit

Komposit merupakan kombinasi dari duamaterial atau lebih yang memiliki fasayang berbeda menjadi suatu material baru

yang memiliki properti lebih baik darikeduanya.

Jika kombinasi ini terjadi dalam skalamakroskopis maka disebut sebagai

komposit.

Jika kombinasi ini terjadi secaramikoroskopis (molekular level) maka

disebut sebagai alloy atau paduan.


6/45

Two types of composites are:

Fiber Reinforced

Composites

Particle Reinforced

Composites


7/45

Particle reinforced composites support higher tensile,

compressive and shear stresses.

Figure 1. Examples for particle-reinforced composites.

(Spheroidized steel and automobile


8/45

The following are some of the reasonswhy composites are selected for certainapplications:

High strength to weight ratio (low density high tensile

strength)

High creep resistance

High tensile strength at elevated temperatures

High toughness


9/45

Examples of Composites• Natural

–Wood

• flexible cellulose fibers held together with

stiff lignin

–Bone

• strong protein collagen and hard, brittleapatite

• Artificial (man-made)

– constituent phases are chemicallydistinct


10/45

Definitions

• Composites often have only twophases

• Matrix phase

– continuous - surrounds other phase

• Dispersed phase

–discontinuous phase

Matrix (light)

Dispersed phase (dark)


11/45

Introduction

• Engineering applications often require unusualcombinations of properties

– esp. aerospace, underwater, and

transportation– can’t be achieved with a single material

– e.g. - aerospace requires strong, stiff, light,and abrasion resistant material

• most strong, stiff materials are denseand heavy

• most light materials are not abrasionresistant

• Solution is in composite materials


12/45

Examples of Composites• Natural

–Wood

• flexible cellulose fibers held together with

stiff lignin

–Bone

• strong protein collagen and hard, brittleapatite

• Artificial (man-made)

– constituent phases are chemicallydistinct


13/45

Figure 16.1 Some examples of composite materials: (a)plywood is a laminar composite of layers of wood veneer, (b)fiberglass is a fiber-reinforced composite containing stiff,strong glass fibers in a softer polymer matrix ( 175), and(c) concrete is a particulate composite containing coarsesand or gravel in a cement matrix (reduced 50%).


14/45

Properties of CompositesDependent on:

• constituent phases

• relative amounts• geometry of dispersed phase

– shape of particles

–particle size–particle distribution

–particle orientation


15/45

Composite Parameters

For a given matrix/dispersedphase system:

• Concentration

• Size

• Shape

• Distribution

• Orientation


16/45

Concentration

SizeShape

Distribution Orientation

Parameters


17/45

Classification of ArtificialComposites

Composites

Particulate Fiber Structural

Continuous Discontinuous

Laminates SandwichPanels

LargeParticle

DispersionStrengthened

Aligned Random


18/45

Particle-ReinforcedComposites

• Divided into two classes

– (based on strengthening mechanism)

• Large particle

– interaction between particles and matrix arenot on the atomic or molecular level

– particle/matrix interface strength is critical

• Dispersion strengthened

– 0.01-0.1 mm particles

– inhibit dislocation motion


19/45

Large Particle CompositesExamples:

• Some polymers with added fillers arereally large particle composites

• Concrete (cement with sand orgravel)

– cement is matrix, sand is particulate


20/45

Large Particle CompositesDesired Characteristics

• Particles should be approximatelyequiaxed

• Particles should be small and evenlydistributed

• Volume fraction dependent ondesired properties


21/45

Large-Particle CompositeMaterials

• All three material types

–metals, ceramics, and polymers

• CERMET (ceramic-metal composite)

– cemented carbide (WC, TiC embeddedin Cu or Ni)

– cutting tools (ceramic hard particles to

cut, but a ductile metal matrix towithstand stresses)

– large volume fractions are used (up to

90%!)


22/45

Large Particle CompositesConcrete

• Concrete is not cement)

–Concrete is the composite of cementand an aggregate (fine sand or coarse

gravel)• Reinforced concrete

–a composite (large particle composite) -

with a matrix which is a composite– steel rods, wires, bars (rebar,

sometimes stretched elastically whileconcrete dries to put system in

compression)


23/45

Dispersion StrengthenedComposites

• Metals and metal alloys– hardened by uniform dispersion of fine particles of a

very hard material (usually ceramic)

• Strengthening occurs through theinteractions of dislocations and theparticulates

• Examples• Thoria in Ni

• Al/Al2O3 sintered aluminum powder SAP

• GP zones in Al


24/45

CERMET Cutting Tool

Light phase - Matrix (Cobalt)

Dark phase- Particulate (WC)


25/45

Figure 16.7 Microstructure of analuminum casting alloy reinforced with

silicon carbide particles. In this case, thereinforcing particles have segregated tointerdendritic regions of the casting( 125). (Courtesy of David Kennedy,Lester B. Knight Cost Metals Inc .)


26/45

Klasifikasi Komposit

Komposit

Partikel Fiber Struktural

Continuous Discontinuous

Laminates SandwichPanels

LargeParticle

DispersionStrengthened

Aligned Random

Berdasarkan Bentuk dari Reinforcementnya


27/45

Fiber sebagai reinforced

Fiber yang digunakan harus:

• Mempunyai diameter yang lebihkecil dari diameter bulknya(matriksnya) namun harus lebihkuat dari bulknya

• Harus mempunyai tensile strengthyang tinggi


28/45

Figure 16.18 Photomicrographs of two fiber-reinforcedcomposites: (a) In Borsic fiber-reinforced aluminum, the fibersare composed of a thick layer of boron deposited on a small-

diameter tungsten filament ( 1000). (From Metals Handbook,

American Society for Metals, Vol. 9, 9th Ed., 1985 .) (b) In thismicrostructure of a ceramic-fiber–ceramic-matrix composite,silicon carbide fibers are used to reinforce a silicon nitridematrix. The SiC fiber is vapor-deposited on a small carbon

precursor filament (

125). (Courtesy of Dr. R.T. Bhatt, NASA

Lewis Research Center .)


29/45


30/45

Matriks yang dipadukan dengan fiber

berfungsi sebagai :• Penjepit fiber

• Melindungi fiber dari kerusakanpermukaan

• Pemisah antara fiber dan juga mencegahtimbulnya perambatan crack dari suatufiber ke fiber lain

• Berfungsi sebagai medium dimanaeksternal stress yang diaplikasikan kekomposit, ditransmisikan dandidistribusikan ke fiber.


31/45

Matriks yang digunakan harus :

• Ductility tinggi• Memiliki modulus elastisitans lebih

rendah daripada fiber

• Mempunyai ikatan yang bagusantara matriks dan fiber

• Biasanya secara umum yang

digunakan adalah polimer dan logam


32/45

a. Short(discontinuous) fiber reinforced composites

Aligned Random

b. Continuous fiber (long fiber) reinforced composites

Fib bi


33/45

Fiber yang biasadigunakan antara lain :

Fibers – Glass– Sangat umun digunakan, karena murah

sering digunakan untuk reinforcementdalam matrik polimer

– Komposisi umum adalah 50–

60 % SiO2dan paduan lain yaitu Al, Ca, Mg, Na, dll.– Moisture dapat mengurangi kekuatan dari

glass fiber– Glass fiber sangat rentan mengalami

static fatik– Biasanya digunakan untuk: piping, tanks,boats, alat-alat olah raga


34/45

Sifat-Sifatnya• Densitynya cukup rendah ( sekitar 2.55g/cc)

• Tensile strengthnya cukup tinggi (sekitar1.8 GPa)

• Biasanya stiffnessnya rendah (70GPa)• Stabilitas dimensinya baik• Resisten terhadap panas

• Resisten terhadap dingin• Tahan korosi


35/45

Keuntungan :

• Biaya murah

• Tahan korosi• Biayanya relative lebih rendah dari komposit

lainnya

Kerugian

• Kekuatannya relative rendah

• Elongasi tinggi

• Keuatan dan beratnya sedang(moderate)

Jenis-jenisnya antara lain :

– E-Glass - electrical, cheaper

– S-Glass - high strength


36/45

Fibers - Aramid (kevlar, Twaron)

Biasanya digunakan untuk : Armor,protective clothing, industrial,sporting goods

Keuntungan :kekutannya cukuptinggi, dan lebih ductile dari carbon


37/45

Carbon Fibers

• Densitaskarbon cukup ringan yaitu sekitar 2.3g/cc

• Struktur grafit yang digunakan untuk membuatfiber berbentuk seperti kristal intan.

• Karakteristik komposit dengan serat karbon :– ringan;

– kekuatan yang sangat tinggi;– kekakuan (modulus elastisitas) tinggi.

• Diproduksi dari poliakrilonitril (PAN), melalui tigatahap proses :

• Stabilisasi = peregangan dan oksidasi;

• Karbonisasi= pemanasan untuk mengurangi O, H, N;

• Grafitisasi = meningkatkan modulus elastisitas.


38/45

Pengaruh Orientasi Fiber

• Parameter Fiber– arrangement with respect to each other

– distribution

– concentration

• Orientasi Fiber– parallel to each other

– totally random– some combination


39/45

Flat flakes sebagai penguat (Flake

composites)

Fillers sebagai penguat (Filler composites)


40/45

Specific Material Properties:Bila dibandingkan dengan engineering materials yang lain,

FRPs sangat competitive ditinjau dari beratnya

Tensile

Strength

s

(Mpa)

Stiffness

E

(Gpa)

Mild Steel

Aluminium

Nylon

ConcreteRandom Fibre FRP

Alligned Fibre FRP

(Load // Fibres)

(Load Fibres)

Specific

Stiffness

E/ r

Specific

Strength

s / r

Density

r

(kg/m3)

7800

2700

1100

24001800

1600

1600

208

70

2.5

4020

200

3

400

200

80

20300

1500

50

1

0.97

0.09

0.630.42

4.69

0.07

1

1.44

1.42

0.163.25

18.3

0.61


41/45

Fiber Material Properties

Steel: density (Fe) = 7.87 g/cc; TS=0.380 GPa; Modulus=207 GPa

Al: density=2.71 g/cc; TS=0.035 GPa; Modulus=69 GPa

b S h


42/45

Fiber Strength


43/45

Structurtal Composite


44/45

©2003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning™

is a trademark used herein under license.

Figure 16.12 (a) Tapes containing aligned fibers can be joined to produce a multi-layered different orientations toproduce a quasi-isotropic composite. In this case, a0°/+45°/90° composite is formed.


45/45

©2003 Brooks/Cole, a division of Thomson Learning, Inc. Thomson Learning™

is a trademark used herein under license.

Figure 16.13 A three-dimensional weave for fiber-reinforced composites.

01 Introduksi Material Komposit

Documents