KOMPOSITE2034304-3 SKS

TEKNIK MESIN S1

FT-UNNES

Maret – Juni 2015

Dr. Rahmat Doni Widodo, ST., MT.

Email : rahmat.doni2015@gmail.com

PENDAHULUAN

Mata Kuliah : KOMPOSIT

Kode Mata Kuliah : E2034304

SKS : 3

Semester : Genap 2014/2015

Staf Pengajar : Rahmat Doni Widodo (RDW)

Tujuan Pengajaran : Memahami jenis- jenis, sifat, proses pabrikasidan penggunaan dari material komposit

Sistem Evaluasi :

Kehadiran : 5 %

Tugas : 15 %

Ujian Tengah Semester (UTS) : 30 %

Presentasi : 15 %

Ujian Akhir Semester (UAS) : 35 %

SATUAN ACARA PENGAJARAN (SAP)

Pertemuan Tanggal Pokok Bahasan

1 5 Maret 2015

Maksud dan tujuan dibuatnya material komposit, struktur, klasifikasi, konsep desain dan aplikasi material komposit.

2 12 Maret 2015

Isotropy dan Anisotropy pada komposit, KarakteristikPenguat dan Matrik, Unindirectional pada Lapisan (Ply), Pabrikasi Woven, Mats dan Reinforce Matrix.

3 19 Maret 2015Definisi struktur Sandwich, Sifat struktur Sandwich, Pabrikasi dan desain struktur Sandwich.

4 26 Maret 2015Konsep dasar desain, bentuk, kerusakan, dan sifat padastruktur Laminate.

5, 6 dan 72, 9 dan 16 April

20015

Konsep dasar sifat mekanik, ketahanan pada: bebandinamis, korosi, temperatur, lelah pada material komposit.

8 23 April 20015 UJIAN TENGAH SEMESTER

SATUAN ACARA PENGAJARAN (SAP)

Pertemuan Tanggal Pokok Bahasan

9 30 April 2015

Sifat elektrik berupa konduktifitas, Volume tahananelektrik, Daya elektrik dan tahanan panas, Efek strain terhadap sifat elektrik, Kuat sambungan mekanikterhadap sifat elektrik pada material komposit.

10 7 Mei 2015Konsep dasar Sifat thermal berupa: Expansi panas, Panasjenis, dan konduktifitas panas pada material komposit.

11 21 Mei 20015Proses pembuatan atau pabrikasi material kompositmelalui proses molding, dan proses selain molding.

12 dan 1328 Mei dan 4 Juni

2015

Aplikasi material komposit untuk konstruksi transportasidan kepentingan lainnya.

14 dan 15 11 dan 18 Juni 2015

Prsentasi dari hasil review jurnal yang berhubungandengan Faktor-fakrot yang mempengaruhi sifat padamaterial komposit melalui review journal penelitian.

25 Juni 2015 Minggu Tenang

16 2 Juli 2015 UJIAN AKHIR SEMESTER

References

Vincent K.S. Choo, Fundamentals of Composite Materials, Knowen Academic Press Inc, 1990

Derek Hull, An Introduction to Composite Materials, Cambridge University Press, 1981.

Deborah D.L. Chung, Composite Materials : Science and Applications Ed.2, Springer-Verlag, 2010.

Suong V. Hoa, Principles of the Manufacturing of Composite Materials, DEStech Publications Inc, 2009.

Sanjay K. Mazumdar, Composites Manufacturing : Materials, Product and Process Engineering, CRC Press, 2002.

References

Daniel Gay, Suong V. Hoa, Stephen W. Tsai, Composite Materials: Design and Applications, CRC Press, 2003.

Campbell F.C., Structural Composite Materials, ASM International, 2010.

Ajayan P.M., Schadler L.S., and Braun P.V., Nanocomposite Science and Technology, Wiley-VCH Verlag, 2003.

Abdul Hamid Zureich and Alan T. Nettles, Composite Materilas : Testing, Design and Acceptance Criteria, ASTM International, 2002.

Jurnal-jurnal hasil penelitian yang relevan denganbahan kajian.

BAHAN KOMPOSIT (COMPOSITE MATERIALS)

Merupakan penggabungan dua macammaterial atau lebih dengan fase yangberbeda.

Untuk skala atomic - mikro , logam, polimer, dankeramik dapat digolongkan KOMPOSIT.

Pd KOMPOSIT bisa terjadi reaksi antar komponenpenyusunnya shg akan muncul fase ketiga ygmemiliki sifat berbeda dari fase pertma maupunfase ke dua

Composite

• Combination of two or more individual materials

• Design goal: obtain a more desirable combination of properties (principle of combined action)

– e.g., low density and high strength

Advantages of Composite Materials

• Stronger and stiffer than metals on a density basis

• Capable of high continuous operating temperatures

• Highly corrosion resistant

• Tailorable thermal expansion properties

• Tunable energy management characteristics

• Outstanding durability

• Low Observable

Disadvantages

- complex production methods

- difficult processing (cutting, forming)

- difficult joining

- often impossible to repair

- sometimes brittle

- high cost

Composites can be found in:-Boat hulls

-The aerospace industry (structural components as well as engines and motors)

-Automotive parts (panels, frames, dashboards, body repairs)

-Bathtubs, hot tubs, swimming pools-Cement buildings, bridges

-Surfboards, snowboards, skis-Golf clubs, fishing poles, hockey sticks

-Trees are technically composite materials, plywood-Electrical boxes, circuit boards, contacts

-Everywhere

Pd Komposit dikenal istilah :

MATRIK (fase Pertama)

REINFORCEMENT (fase Kedua)

Fase Pertama (Matrik) berfungsi sbg PENGIKAT

Fase Kedua(Reinforcement) berfungsi sbg PENGUAT

KLASIFIKASI KOMPOSIT:

1. CMC (Ceramic Matrix Composites)

2. MMC (Metal Matrix Composites)

3. PMC (Polymer Matrix Composites)

Matrix

- continuous phase

- joins the reinforcement together

- transfers external loads onto the reinforcement

- determines external shape

- materials:- metals (MMC): Al, Mg, Ti, Fe, Ni, Co- ceramics (CMC): concrete, SiC, Al2O3, - polymers: polyesters, polyamides, epoxy resins, asphalt

Reinforcement

- embedded into matrix

- improvement of matrix properties: stiffness, hardness, fracture toughness, thermal shock resistance, wear resistance, friction coefficient, thermal conductivity

- different forms: powder, fibers (continuous-discontinuous, aligned-random), laminates

- materials:- metals: wires: Fe, powders: W, Mo- ceramics: fiberes: glass, SiC and carbon; particles: SiCand Al2O3, metal oxides- polymers: Kevlar, Nylon

METALS

POLYMERS

CERAMICS

Metal-Polymer Composites atauMetallic Matrix Composites (MMC)

Metal-Ceramic Composites atauMineral Matrix Composite/Ceramic Matrix Composites (CMC)

Ceramic-Polymer Composite atauOrganik Matrix Composite/ Polymer Matrix Composites (PMC)

Metal Matrix Composites (MMC)

• Metal matrix composites (MMCs), as the nameimplies, have a metal matrix. Examples of matricesin such composites include aluminum, magnesium,and titanium.

• Typical fibers include carbon and silicon carbide.

• Metals are mainly reinforced to increase or decreasetheir properties to suit the needs of design. Forexample, the elastic stiffness and strength of metalscan be increased, and large coefficients ofthermal expansion and thermal and electricconductivities of metals can be reduced, by theaddition of fibers such as silicon carbide.

Advantages of MMC’s

• Metal matrix composites are mainly usedto provide advantages over monolithicmetals such as steel and aluminum.These advantages include higher specificstrength and modulus by reinforcing low-density metals, such as aluminum andtitanium; lower coefficients of thermalexpansion by reinforcing with fibers withlow coefficients of thermal expansion, suchas graphite; and maintaining propertiessuch as strength at high temperatures.

Advantages of MMC’s

• Advantages over polymer matrixcomposites. These include higher elasticproperties; higher service temperature;insensitivity to moisture; higher electricand thermal conductivities; and betterwear, fatigue, and flaw resistances.

• The drawbacks of MMCs over PMCsinclude higher processing temperaturesand higher densities.

Fabrication MethodFabrication methods for MMCs are varied. Onemethod of manufacturing them is diffusion bondingwhich is used in manufacturing boron/aluminumcomposite parts. A fiber mat of boron is placedbetween two thin aluminum foils about 0.05 mmthick. A polymer binder or an acrylic adhesive holdsthe fibers together in the mat. Layers of these metalfoils are stacked at angles as required by the design.The laminate is first heated in a vacuum bag toremove the binder. The laminate is then hot pressedwith a temperature of about 500°C and pressure ofabout 35 MPa in a die to form the required machineelement.

Applications of MMC’s

• Space: The space shuttle usesboron/aluminum tubes to support itsfuselage frame. In addition todecreasing the mass of the spaceshuttle by more than 145 kg,boron/aluminum also reduced thethermal insulation requirements becauseof its low thermal conductivity. The mastof the Hubble Telescope uses carbon-reinforced aluminum.

• Military: Precision components of missileguidance systems demand dimensionalstability — that is, the geometries of thecomponents cannot change during use.Metal matrix composites such asSiC/aluminum composites satisfy thisrequirement because they have highmicroyield strength. In addition, thevolume fraction of SiC can be varied tohave a coefficient of thermal expansioncompatible with other parts of the systemassembly.

• Transportation: Metal matrixcomposites are finding use now inautomotive engines that are lighter thantheir metal counterparts. Also, becauseof their high strength and low weight,metal matrix composites are thematerial of choice for gas turbineengines.

Ceramic Matrix Composites (CMC)

Ceramic matrix composites (CMCs) have aceramic matrix such as alumina calciumalumino silicate reinforced by fibers suchas carbon or silicon carbide.

Advantages of CMC’s

• High strength,

• Hardness,

• High service temperature limits for ceramics,

• Chemical inertness, and

• Low density.

However, ceramics by themselves have low fracture toughness. Under tensile or impactloading.

Reinforcing ceramics with fibers, such assilicon carbide or carbon, increases theirfracture toughness because it causesgradual failure of the composite. Thiscombination of a fiber and ceramic matrixmakes CMCs more attractive forapplications in which high mechanicalproperties and extreme servicetemperatures are desired.

Advantages of CMC’s

Manufacturing Method of CMC

One of the most common methods tomanufacture ceramic matrix composites is calledthe hot pressing method. Glass fibers incontinuous tow are passed through slurryconsisting of powdered matrix material, solventsuch as alcohol, and an organic binder (Figure1.31). The tow is then wound on a drum and driedto form prepreg tapes. The prepreg tapes can nowbe stacked to make a required laminate. Heatingat about 500°C burns out the binder. Hot pressingat high temperatures in excess of 1000°C andpressures of 7 to 14 MPa follows this.

Carbon Carbon Composites

Carbon–carbon composites use carbon fibers in a carbon matrix. Thesecomposites are used in very high-temperature environments of up to 3315°C, and are 20 times stronger and 30% lighter than graphite fibers.

Carbon Carbon Composites

Carbon–carbon composites use carbon fibers in a carbon matrix. Thesecomposites are used in very high-temperature environments of up to 3315°C, and are 20 times stronger and 30% lighter than graphite fibers.

Advantages of C-C Composites

• Carbon is brittle and flaw sensitive likeceramics. Reinforcement of a carbon matrixallows the composite to fail gradually and alsogives advantages such as ability to withstandhigh temperatures, low creep at hightemperatures, low density, good tensile andcompressive strengths, high fatigue resistance,high thermal conductivity, and high coefficient offriction.

• Drawbacks include high cost, low shear strength,and susceptibility to oxidations at hightemperatures.

Processing a c–c compositeLow-pressure carbonizationA graphite cloth is taken, impregnated by resin(such as phenolic, pitch, and furfuryl ester), and laidup in layers. It is laid in a mold, cured, and trimmed.The part is then pyrolized, converting the phenolicresin to graphite. The composite is thenimpregnated by furfuryl alcohol. The process drivesoff the resin and any volatiles. The process isrepeated three or four times until the level ofporosity is reduced to an acceptable level. Eachtime, this process increases its modulus andstrength. Because carbon–carbon compositesoxidize at temperatures as low as 450°C, an outerlayer of silicon carbide may be deposited.

• Mechanical fasteners: Fasteners needed forhigh temperature applications are made ofcarbon–carbon composites because they loselittle strength at high temperatures.

NATURAL FIBERS

• abaca, coconut, flax, hemp, jute, kenaf and sisal are the most common — are derived from the bast or outer stem of certain plants.

• They have the lowest density of any structural fiber but possess sufficient stiffness and strength for some applications.

• The automotive industry, in particular, is using these fibers in traditionally unreinforced plastic parts and even employs them as an alternative to glass fibers. European fabricators hold the lead in use of these materials, in part because regulations require automobile components to be recyclable.

Types of Natural Fiber

Banana Fiber

Hemp Fiber

Jute Fiber

Kenaf Fiber

Sugarcane-

Bagasse

Fiber

Applications1. Car parts

Door

panels

Exterior body

parts

Car

Hood

Front bumpers

and fenders

Various interior

parts

Natural fiber composites vs. synthetic fiber composites

Study Materials Application Performance

Schmidt & Meyer

(1998)

Hemp-EPDM-PP

vs. GF-EPDM-

PP

Auto Insulation

component (Ford

car)

Hemp fibers are

able to replace

glass fibers

Diener & Siehler

(1999)

GF-PP vs. Flax-

PP

Auto car panel

(Mercedes A car)

Successfully

passed all test

Wotzel et al.

(1999)

Hemp – Epoxy

vs. ABS

Auto side panel Do not discuss

the performance

Corbiere-Nicollier

et al. (2001)

China reed-PP

vs. Glass-PP

Transport pallet Satisfying

service

requirement

Source : Joshi et al. (2003)

Weight Reduction

Component Study NFRP

component

Base

component

Auto side panel Wotzel et al. 820 g (hemp-

epoxy)

1125 g (ABS)

Auto insulation Schmidt &

Meyer (1998)

2.6 kg (hemp-

PP)

3.5 kg (GF-PP)

Transport-Pallet Corbiere-

Nicollier et al.

(2001)

11.77 kg (China

reed – PP)

15 kg (GF – PP)

Source : Joshi et al. (2003)

2. Recreation and Leisure

Decking product

Railing

Patio furniture

3. Insulated Roofing

Roof

sandwich

with foam

core

Roof

sandwich

structure

with

bamboo

core

Applications4. Door panel

Mechanics Terminology

The approach to analyze the mechanical behaviorof composite structures is:

1. Find the average properties of a composite plyfrom the individual properties of theconstituents. Properties include stiffness,strength, thermal, and moisture expansioncoefficients. Note that average properties arederived by considering the ply to behomogeneous. This is called the micromechanicsof a lamina.

2. Develop the stress–strain relationships for a unidirectional/bidirectional lamina. Loads may be applied along the principal directions of symmetry of the lamina or off-axis. Also, one develops relationships for stiffness, thermal and moisture expansion coefficients, and strengths of angle plies. Failure theories of a lamina are based on stresses in the lamina and strength properties of a lamina. This is called the macromechanics of a lamina.