01. Pengenalan Material Komposit.pdf 2i1c35

Teknologi Komposit

Class info • Credits

: 3

• Semester

: 6

• ELO : students are able to explain composite materials, process and applications, calculate the mechanical and physical properties using Rule of Mixture, and understand the mechanical aspect of laminate composite • Grading Systems

: Homework, In Class Assgn., Midtest

• Textbook

:

• Hull, D., An Introduction to Composite Materials. 1981 • Matthew, F.L. and R.D. Rawlings, Composites Materials: Engineering and Science. 1993 • Bryan Harris, Engineering Composites Materials. 1999 • Gibson R.F., Principle of Composites Materials Mechanics. 1994

Class Schedule Date

Subject

Note

WNP

08/09 Feb 2017

SAP. Class Introduction. Definition & classification of composites

WNP

15/16 Feb 2017

Classification and function of matrix and reinforcement.

WNP

22/23 Feb 2017

Types of particle and fiber reinforcement

WNP

01/02 Maret 2017

Interfaces, interphases, angle

In Class Assignment

WNP

08/09 Maret 2017

WNP

15/16 Maret 2017

Homework

WNP

22/23 Maret 2017

Adsoprtion and wetting, interdiffusion bonding, electrostatic attraction, mechanical interlocking, bonding strength Effect of fiber length and orientation, effect of loading direction, matrix and fiber loading ratio Rule of mixture calculation

29/30 Maret 2017

Mid Test

AZ

05/06 April 2017

Metal matrix composites

AZ

12/13 April 2017

Ceramic matrix composites

AZ

19/20 April 2017

Polymer matrix composites

AZ

26/27 April 2017

Nano composites

AZ

03/04 Mei 2017

Composites laminates

AZ

10/11 Mei 2017

Laminate analysis, strength of laminate

17/18 Mei 2017

Final Test

Class Rules • Attendance is important but not mandatory • • • •

No sleep in class Candies and drinks are allowed Late arrival is acceptable Don’t be noisy

• Homework submission

• Submit electronically • Minus 10 points per day for late submission • No plagiarism, no copy-paste

• Mid test & Final test

• No cheating, no cell-phone, no restroom-break • Your answer-book will not be returned • Any complaint, please come to my office directly

THE WORLD OF MATERIALS

THE WORLD OF MATERIALS

TUJUAN PENGAJARAN 

Definitions in composite materials  Dispersed phase, matrix



Structure of composites  Particle-reinforced  Fiber reinforced  Structural composites

PENGERTIAN KOMPOSIT 

Komposit merupakan kombinasi dari dua material atau lebih yang memiliki fasa yang berbeda menjadi suatu material baru yang memiliki properti lebih baik dari keduanya.



Jika kombinasi ini terjadi dalam skala makroskopis maka disebut sebagai komposit.



Jika kombinasi ini terjadi secara mikoroskopis (molekular level) maka disebut sebagai alloy atau paduan.

PENGERTIAN KOMPOSIT 

Composites are formed from two or more types of materials. Examples include polymer/ceramic and metal/ceramic composites.



Composites are used because overall properties of the composites are superior to those of the individual components. For example: polymer/ceramic composites have a greater modulus than the polymer component, but aren't as brittle as ceramics.

DEFINISI KOMPOSIT 

Multiphase material

 Usually exhibits properties of both phases  Usually improves performance over either individual phase 

Composites have already been discussed

 Multiphase metal alloys, or ceramics or polymers

 Example, pearlitic steels, alt. Layers a + fe3c 

There are also composites spanning materials classes (e.g. ceramic and metals)

JENIS KOMPOSIT

Fiber Reinforced Composite

Particle Reinforced Composite

JENIS KOMPOSIT Particle – reinforced composites higher tensile, compressive and shears stresses Examples for particle – reinforced composites. (spheroidized steel and automobile tire)

APLIKASI KOMPOSIT 

Engineering applications often require unusual combinations 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 dense and heavy – most light materials are not abrasion resistant 

Solution is in composite materials

CONTOH KOMPOSIT 

Natural  Wood  flexible cellulose fibers held together with stiff lignin  Bone  strong protein collagen and hard, brittle apatite

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Artificial (man-made)  Constituent phases are chemically distinct

KLASIFIKASI KOMPOSIT BUATAN

SIFAT KOMPOSIT Depends on:  Constituent phases  Relative amounts  Geometry of dispersed phase – Size, shape, etc.

PARAMETER KOMPOSIT For a given matrix/dispersed phase system:  Concentration  Size  Shape  Distribution  Orientation

PARAMETER KOMPOSIT

KLASIFIKASI KOMPOSIT BUATAN

PARTICULATE – REINFORCED COMPOSITES 

Divided into two classes  (based on strengthening mechanism)



Large particle  interaction between particles and matrix are not on the atomic or molecular level  particle/matrix interface strength is critical



Dispersion strengthened  0.01-0.1 mm particles  inhibit dislocation motion

PARTICULATE COMPOSITE Large particle  Interaksi antara partikel dan matrik terjadi tidak dalam skala atomik atau molekular  Partikel seharusnya kecil dan terdistribusi merata  Contoh dari large particle composit: cement dengan sand atau gravel, cement sebagai matriks dan sand sebagai partikel

LARGE PARTICLE COMPOSITES - MATERIALS 

All three material types  Metals, ceramics, and polymers

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CERMET (ceramic-metal composite)  Cemented carbide (WC, TiC embedded in Cu or Ni)  Cutting tools (ceramic hard particles to cut, but a ductile metal matrix to withstand stresses)  Large volume fractions are used (up to 90%!)

LARGE PARTICLE COMPOSITES CERMET Cutting Tool Light phase - Matrix (Cobalt) Dark phase- Particulate (WC)

LARGE PARTICLE COMPOSITES Examples:  Some polymers with added fillers are really large particle composites

 Concrete (cement with sand or gravel) – cement is matrix, sand is particulate

LARGE PARTICLE COMPOSITES - CONCRETE 

Concrete is not cement)  Concrete is the composite of cement and 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 while concrete dries to put system in compression)

LARGE PARTICLE COMPOSITES Desired Characteristics  Particles should be approximately equiaxed  Particles should be small and evenly distributed  Volume fraction dependent on desired properties

VOLUME FRACTION IN LARGE PARTICLE COMPOSITES 

Elastic modulus is dependent on the volume fraction



“Rule of mixtures” equation  E- elastic modulus, V- volume fraction, m- matrix, p- particulate

 upper bound

Ec  EmVm  EpVp

 lower bound

Em E p Ec  Ep Vm  EmVp

RULE OF MIXTURES

DISPERSION STRENGTHENED COMPOSITES 

Metals and metal alloys  Hardened by uniform dispersion of fine particles of a very hard material (usually ceramic)

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Strengthening occurs through the interactions of dislocations and the particulates

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Examples  Thoria in Ni  Al/Al2O3 sintered aluminum powder SAP  GP zones in Al

KLASIFIKASI KOMPOSIT BUATAN

FIBER – REINFORCED COMPOSITES Fiber yang digunakan harus:  Mempunyai diameter yang lebih kecil dari diameter bulknya (matriksnya) namun harus lebih kuat dari bulknya  Harus mempunyai tensile strength yang tinggi

FIBER – REINFORCED COMPOSITES Matriks yang dipadukan dengan fiber berfungsi sebagai :  Penjepit fiber

 Melindungi fiber dari kerusakan permukaan  Pemisah antara fiber dan juga mencegah timbulnya perambatan crack dari suatu fiber ke fiber lain

 Berfungsi sebagai medium dimana eksternal stress yang diaplikasikan ke komposit, ditransmisikan dan didistribusikan ke

fiber.

FIBER – REINFORCED COMPOSITES Matriks yang digunakan harus :  Ductility tinggi  Memiliki modulus elastisitans lebih rendah daripada fiber  Mempunyai ikatan yang bagus antara matriks dan fiber  Biasanya secara umum yang digunakan adalah polimer dan logam

FIBER – REINFORCED COMPOSITES

GLASS FIBERS Fibers – Glass  Sangat umun digunakan, fiber yang murah adalah glass fiber yang sering digunakan untuk reinforcement dalam matrik polimer  Komposisi umum adalah 50 – 60 % SiO2 dan 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

GLASS FIBERS Sifat-Sifatnya  Densitynya cukup rendah ( sekitar 2.55 g/cc)  Tensile strengthnya cukup tinggi (sekitar 1.8 GPa)  Biasanya stiffnessnya rendah (70GPa)  Stabilitas dimensinya baik  Resisten terhadap panas

 Resisten terhadap dingin  Tahan korosi

GLASS FIBERS 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

ARAMID FIBERS Fibers - Aramid (kevlar, Twaron)  Biasanya digunakan untuk : Armor, protective clothing, industrial, sporting goods  Keuntungan :kekutannya cukup tinggi, dan lebih ductile dari carbon

CARBON FIBERS Carbon Fibers 

Densitas karbon cukup ringan yaitu sekitar 2.3 g/cc



Struktur grafit yang digunakan untuk membuat fiber berbentuk seperti kristal intan.

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Karakteristik komposit dengan serat karbon : – ringan; – kekuatan yang sangat tinggi; – kekakuan (modulus elastisitas) tinggi.



Diproduksi dari poliakrilonitril (PAN), melalui tiga tahap proses : – Stabilisasi = peregangan dan oksidasi; – Karbonisasi= pemanasan untuk mengurangi O, H, N; – Grafitisasi = meningkatkan modulus elastisitas

KLASIFIKASI KOMPOSIT BUATAN

STRUCTURAL COMPOSITES 

Definition  Composed of both homogeneous and composite materials

 Properties depend on constituent materials and on geometrical design of the elements 

Types  Laminar composites  Sandwich s

STRUCTURAL COMPOSITES

KOMPOSIT LAMINAR 

Two dimensional sheets or s with a preferred high-strength direction  Q. What is a natural example of this?  A. Wood

 Q. What is a man made example  A. Plywood - Layers are stacked and subsequently bonded together so that the high strength direction varies

KOMPOSIT SANDWICH 

Two strong outer sheets (called faces) separated by a layer of

less dense material or core (which has lower E and lower strength) 



Core  

Separates faces Resists deformation perpendicular to the faces

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Often honeycomb structures

Used in roofs, walls, wings

KOMPOSIT SANDWICH