Wear Behavior of Carbon Nanotube (CNT)Short Natural Fiber Reinforced Epoxy Composite.

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UNIVERSITI TEKNIKAL MALAYSIA MELAKA

Wear Behavior of Carbon Nanotube (CNT)/Short Natural Fiber

Reinforced Epoxy Composite

This report submitted in accordance with requirement of the Universiti Teknikal Malaysia Melaka (UTeM) for the Bachelor Degree of Manufacturing Engineering

(Engineering Materials) (Hons.)

MOHD ALI BIN ROSLI B051010172 890211045127

FACULTY OF MANUFACTURING ENGINEERING 2013

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UNIVERSITI TEKNIKAL MALAYSIA MELAKA

BORANG PENGESAHAN STATUS LAPORAN PROJEK SARJANA MUDA

TAJUK: Wear Behavior of Carbon Nanotube (CNT)/Short Natural Fiber Reinforced Epoxy Composite

SESI PENGAJIAN: 2012/2013 Semester 1 Saya MOHD ALI BIN ROSLI

mengaku membenarkan Laporan PSM ini disimpan di Perpustakaan Universiti Teknikal Malaysia Melaka (UTeM) dengan syarat-syarat kegunaan seperti berikut: 1. Laporan PSM adalah hak milik Universiti Teknikal Malaysia Melaka dan penulis. 2. Perpustakaan Universiti Teknikal Malaysia Melaka dibenarkan membuat salinan

untuk tujuan pengajian sahaja dengan izin penulis.

3. Perpustakaan dibenarkan membuat salinan laporan PSM ini sebagai bahan pertukaran antara institusi pengajian tinggi.

4. **Sila tandakan (√)

SULIT

TERHAD

TIDAK TERHAD

(Mengandungi maklumat yang berdarjah keselamatan atau kepentingan Malaysiasebagaimana yang termaktub dalam AKTA RAHSIA RASMI 1972)

(Mengandungi maklumat TERHAD yang telah ditentukan oleh organisasi/badan di mana penyelidikan dijalankan)

Alamat Tetap:

No 53 Jalan TTP 1 Taman Tambak Paya Permai, 75460 Melaka

Tarikh: 28 Jun 2013

Disahkan oleh:

Cop Rasmi:

Tarikh: _______________________ ** Jika Laporan PSM ini SULIT atau TERHAD, sila lampirkan surat daripada pihak berkuasa/organisasi berkenaan dengan menyatakan sekali sebab dan tempoh laporan PSM ini perlu dikelaskan sebagai SULIT atau TERHAD.

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DECLARATION

I hereby, declared this report entitled “Wear Behavior of Carbon Nanotube (CNT)/Short Natural Fiber Reinforced Epoxy Composite” is the result of my

own research excepted as cited in the references

Signature : ………

Author’s Name : ………

Date : ………

MOHD ALI BIN ROSLI 28 JUN 2013

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APPROVAL

This report is submitted to the Faculty of Manufacturing Engineering of UTeM as a partial fulfillment of the requirements for the degree of Bachelor of Manufacturing Engineering (Engineering Materials) (Hons.). The member of the supervisory is as follow:

……… (Principal Supervisor)

……… (Co - Supervisor)

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ABSTRAK

Prestasi sifat tribologi serat semulajadi polimer komposit didapati telah berjaya di tingkatkan, tetapi, beberapa faktor perlu diambi kira sebelum komposit ini diterima pakai dengan meluas berbanding penggunaan serat sintetik. Maka, ianya dipercayai bahawa pemerbadanan funtionalized nanomaterial dapat membantu meningkatkan lagi prestatsi tribologi serat semulajadi polimer komposit. Fokus kajian ini bertujuan untuk menganalisa sifat kehausan karbon nanotuib (CNT) dan serat kenaf yang pendek epoksi komposit (EP/KNF/CNT) pada kadar fungsi CNT yang berbeza. Komposisi komposit telah dihasilkan dari kuantiti malar 4 wt% serat kenaf dan kadar campuran CNT yang berbeza iaitu 0.1, 0.3 dan 0.5wt%. Bagi memastikan daya lekatan antara serat dan matrik, serat kenaf telah di rawat dengan 6% natrium hidroksida dan fungsi karboksil CNT telah digunakan. Komposit yang dibentuk melalui process vacuum casting menunjukkan kadar liang kosong rendah dari 1%. Ujian tribologi ke atas komposit telah dijalankan pada daya normal 40 N, pada dua kelajuan yang berbeza (1 dan 2 m/s) untuk jarak sejauh 3.75 km. Umumnya, penambahan serat kenaf telah menurunkan kadar spesifik kehausan epoksi dan penambahan CNT meningkatkan lagi ketahanan kehausan komposit. Bagaimanapun, kadar spesifik kehausan pada 1 m/s lebih tinggi dari 2 m/s kerana abrasive wear diperhatikan telah berlaku pada halaju 1 m/s manakala adhesive wear berlaku pada halaju yang tinggi. Daripada semua komposit, EP/KNF/CNT0.5 komposit menunjukkan kadar ketahanan kehausan yang hebat dengan 90.2% peningkatan pada 1 m/s dan 75.4% peningkatan pada 2 m/s halaju luncur berbanding epoksi tulen. Sebaliknya, terdapat perubahan yang tidak menentu pada pekali geseran disebabkan oleh perubahan kestabilan dimensi komposit terhadap haba geseran yang terhasil menghampiri paras suhu peralihan kaca komposit.

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ABSTRACT

Tribological performance of natural fiber reinforced polymer composite is found to be improved but there are some consideration that need to be adressed before natural fiber-reinforced polymer composite gain widespread acceptance as compared to synthetic fiber ones. Thus, it is perceived that incorporation of functionalized nanomaterials may help to improve the tribological behavior of the natural fiber reinforced polymer composite. This study aimed to investigate the dry sliding wear behavior of carbon nanotubes (CNT) and short kenaf fiber reinforced epoxy (EP/KNF/CNT) composite as a function of CNT loading. The composition of the composite was made up of a constant 4 wt% of kenaf fiber and varying CNT loading at 0.1, 0.3 and 0.5 wt%. To ensure better fiber-matrix interfacial adhesion, the kenaf fiber was treated with 6% sodium hydroxide and carboxyl-functionalized CNT was used. The composite fabricated via vacuum casting technique which exhibited less than 1% of void inclusion. Tribological testing of the composite was conducted at 40N load at two different sliding velocities (1 and 2 m/s) for a distance of 3.75 km. Generally, addition of kenaf fiber reduced the specific wear rates of pristine epoxy and further incorporation of CNT enhanced the wear resistance of the composite. However, it was noted that the specific wear rates at 1 m/s is higher than that of 2 m/s because abrasive wear was observed in the former one while adhesive wear was more profound in the latter. Among all, EP/KF/CNT0.5 composite showed a superior wear resistance behaviour with 90.2% improvement at 1 m/s and 75.4% improvement at 2 m/s sliding velocity as compared to the pristine epoxy. On the other hand, there was erratic change on the coefficient of friction of the composite due to the dimensional instability of the composite in regard to frictional heat generated which was closed to the glass transition temperature of the composite.

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DEDICATION

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ACKNOWLEDGEMENT

First and foremost, all praise to the Most Gracious and the Most Merciful Allah for giving the time and opportunity to complete this PSM project successfully. Without His help, none of these could be done smoothly.

Deepest gratitude goes to my beloved parents; Mr. Rosli B. Mohd Deni and Mrs. Ramlah Bt. Yunos for their endless love. Their support and encouragement has seen me through tumultuous times. A deep and sincere appreciation goes to my supervisor, Ms Chang Siang Yee for her guidance, advice, concern, and understanding throughout the PSM project. She was very helpful and committed in simulating suggestion and encauragement. In addition, I would like to express my appreciation to my co-supervisor, Prof Qumrul Ahsan, who always showered me with new knowledge and assisted me in doing this project. Without them, this project may not be completed successfully.

Lots of appreciation also goes to the my friends especially Nurul Noor Nadhirah, Siti Aisyah, Nor Fariha, Nor Effendy, Mohd Firdaus, Safuan, Mohd Irwan and all BMFB 09/13 students for their continuous support in completing this project. The last but not least, special thanks to my family, lecturers and lab technician for giving in so much, either directly or indirectly, to help me to complete the project. Your help was unconditional and thank you very much.

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TABLE OF CONTENT

Abstrak i

Abstract ii Dedication iii

Acknowledgement iv Table of Content v

List of Tables viii

List of Figures ix

List Abbreviations, Symbols and Nomenclatures xii

CHAPTER 1: INTRODUCTION 1

1.1 Background of Study 1

1.2 Problem Statement 4

1.3 Objective 5

1.4 Scope 5

CHAPTER 2: LITERATURE REVIEW 6

2.1 Tribology 6

2.1.1 Classification of Wear 7

2.2 Signification Polymer Matrix Composite In Tribology 8

2.3 Tribology Characterization of Polymer Composite 12

2.3.1 Effect of Operating Parameter 13

2.3.2 Polymer Matrix Response 14

2.3.2.1 Epoxy 15

2.3.3 Effect of Fiber Reinforcement 17 2.3.4 Effect of Micro- and Nano-Fillers 18 2.3.5 Hybrid Composite 19 2.3.6 Role of Carbon Nanotubes 21 2.4 Natural Fiber Reinforced Composite 26

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2.4.1.1 Kenaf Fiber 29

2.4.2 Drawback of Natural Fiber 31

2.4.3 Affect of Treatment on Natural Fiber 33 2.4.4 Thermal Behaviour of Natural Fiber Reinforced Composite 34 2.4.5 Tribological Behaviour of Natural Fiber Reinforced Composite 35 2.5 Overview on Polymer Composite Fabrication 38

2.5.1 Vacuum Casting 40

CHAPTER 3 : METHODOLOGY 42

3.1 Materials 42

3.1.1 Epoxy and Hardener 42

3.1.2 Kenaf Fiber 43

3.1.3 Carbon Nanotubes 44

3.14 Sodium hydroxide 45

3.2 Methods 46

3.2.1 Raw Material Preparation 46

3.2.1.1 Chemical Treatment 46

3.2.1.2 Pulverization Process 46

3.2.2 Raw Material Characterization 47

3.2.1.1 Fourier Transform Infrared (FTIR) 47 3.2.2.2 Scanning Electron Microscopy (SEM) 48

3.2.3 Dispersion and Mixing Method 48

3.2.4 Composite Fabrication 50

3.2.5.1 Master Pattern Fabrication 50

3.2.5.2 Silicon Rubber Mold Fabrication 52

3.2.5.3 Vacuum Casting Process 54

3.2.5.4 Sample Cutting and Polishing 57

3.2.5 Physical Characterization 58

3.2.6.1 Density Measurement 58

3.2.6.2 Void Content Measurement 59

3.2.6 Composite Characterization 60

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3.2.7 Wear Test 61

3.2.8 Microscopic Observation 62

3.2.9 Flow Chart Methodology 63

CHAPTER 4 : RESULTS & DISCUSSION 64

4.1 Characterization of raw materials 64

4.1.1 Scanning electron microscopy 64

4.1.1.1 Effect of alkaline treatment 64

4.1.1.2 Effect of pulverization 65

4.1.2 Fourier transform infrared spectroscopy 66

4.1.2.1 Kenaf fiber 66

4.1.2.2 Multi-walled carbon naotube 67

4.2 Characterization of composite 68

4.2.1 Density measurement 68

4.2.2 Void content 70

4.2.3 Differential scanning calorimetry 71

4.3 Tribological testing 73

4.3.1 Wear performance of composite 73

4.3.2 Frictional characteristic of composite 82

CHAPTER 5: CONCLUSIONS & FUTURE WORK 84

5.1 Conclusions 84

5.2 Future work 86

REFERENCES

APPENDICES

Gantt Chart PSM I Gantt Chart PSMII

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viii

LIST OF TABLES

2.1 Representative friction and wear application of polymer and composite (Tuszynski, 1995)

2.2 Common polymeric material use in tribology (Stachowiak, 2005) 14 2.3 Typical properties of epoxy (Matthews et al., 1999) 16 2.4 Physical and mechanical properties of some natural fibers and

synthetic fibers.

2.5 Properties of filled/reinforced polypropylene composite (Rowel et al as cite in Akil et at., 2011)

2.6 Common manufacturing technique for PMC (Matthew, 1999) 39

3.1 Product specification of EpoxAmite 100 Epoxy mixed with 102 MEDIUM Hardener

3.2 3.3

Geometry of MWCNTs

Chemical and physical data of NaOH

44 45 3.4 3.5 4.1 4.2 4.3 4.4

Nomenclature and composition of CNT/KNF/EP hybrid composite

Mixing time of the mixture

Density measurement of composite

Void content measurement of composite EP/KNF/CNT composite

Specific wear rates of composite

Improvement in specific wear rates of composites at different sliding velocity as compared to pristine epoxy

49 57 68 70 73 74

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LIST OF FIGURES

2.1 Basic chemical structure of epoxy groups 15 2.2

2.3

Contact mode of SCFRP composite with additional nanoperticles (Chang et. al., 2010)

Chemical reaction of MWCNT-COOH and epoxy matrix (Theodore et al., 2010)

20 22

2.4 2.5

Classification of natural fiber (Akil et at., 2011) Kenaf Stalk (Aji et al., 2009)

28 30 2.6 Fiber orientation respect to the sliding direction (Chin et al.,

2009)

3.1 Raw kenaf fiber 43

3.2 Multi-walled carbon nanotubes 44 3.3 Pulverizer (Material Labs, FKP) 47 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 Ultrasonicator

2D drawing with detail dimension

Fuse deposition machine (AMC lab, FKP) Master pattern

Step in producing Silicone rubber Mold a) Lower half of mold b) Completed mold Vacuum Casting Machine (AMC Lab, FKP) Vacuum casting component

MCP 5/10 manual Control Panel Vacuum-casted pristine epoxy sample.\

Electronic Densimeter (MD-300S, AlfaMirage, Japan) Differential Scanning Calorimetry (Polymer Lab, FKP) Inverted Microscope (Tribology Lab, FKM)

Flow Chart Methodology

49 51 51 52 52 53 54 55 56 57 58 60 62 63

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x 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10 4.11 4.12

SEM micrograph of surface morphology of (a) untreated and (b) treated kenaf fiber with 6% NaOH solution for 4 hours.

Pulverized kenaf fiber

FTIR spectrum of untreated- and treated kenaf fiber FTIR spectrum of MWCNT-COOH

Measured and theoretical density of composites Void content of composites

DSC scan

Glass transition temperature of pristine epoxy and its composites Comparison of specific wear rates of composite in conjuction with different sliding velocities with the constant load of 40 N and sliding distance of 3.75 km.

Macro view of wear surface of composite at normal load 40 N for constant sliding distance of 3.75 km at different sliding speed of 1 and 2 m/s. Arrow indicates the sliding direction.

Epoxy wear surface at, a) 1m/s b) 2 m/s sliding velocities with normal load 40 N and constant sliding distance of 3.75 km. Remarks: (Sd-sliding direction, Ck-Crack, Ad-Adherence of wear debris, Fc-Fatigue cracking, Rg-rough surface, Sm-smooth surface, Sc-scratches)

Formation of back transfer film on the wear surface of pristine epoxy at 2 m/s sliding velocity with normal load 40 N and constant sliding distance 3.75 km.

65 66 66 67 69 70 71 72 74 76 77 78 4.13 4.14 4.15

Wear Epoxy/Kenaf fiber at a) 1m/s b) 2m/s. (Remarks : Sd-sliding direction, Ep-epoxy, Kf- Kenaf fiber, Db-debonding, Wear surface of (a) EP/KNF/CNT/0.1 and (b) EP/KNF/CNT0.5, at 1 m/s sliding velocity with normal load 40 N and constant sliding distance of 3.75 km. (Remarks: Sd-sliding direction, F-fiber, Fb-Fiber bending)

Sample condition during dry sliding wear testing at 2 m/s sliding velocity with normal load 40 N and constant sliding distance of 3.75 km. (a) EP (b) EP/KNF, (c) EP/KNF/CNT0.1 and (d)

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xi 4.16

4.17

4.18

EP/KNF/CNT0.5

Protruding effect of pristine epoxy at 2 m/s sliding velocity with normal load 40 N and constant sliding distance of 3.75 km.

Frictional heat of composite at 2m/s sliding speed with 40 N normal loads at constant sliding distance of 3km.

Comparison of coefficient of friction of EP/KNF/CNT composite at different sliding velocity (1 and 2 m/s) with normal load 40 N at constant sliding distance of 3.75 km

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xii

LIST OF ABBREVIATIONS, SYMBOLS AND

NOMENCLATURE

C - Carbon

CMC - Ceramic Matrix Composite

CNT - Carbon Nanotube

COOH - Carboxylic Groups

CuF - Fluoride Copper

CuO - Oxide copper

CuS - Sulfide Copper

EP - Epoxy

EP/KNF - Epoxy/ 4wt% Kenaf

EP/KNF/CNT0.1 - Epoxy/ 4wt% Kenaf/Carbon nanotube 0.1wt% EP/KNF/CNT0.3 - Epoxy/ 4wt% Kenaf/Carbon nanotube 0.3wt% EP/KNF/CNT0.5 - Epoxy/ 4wt% Kenaf/Carbon nanotube 0.5wt% FTIR - Fourier Transform Infrared

H - Hydrogen

MMC - Metal Matrix Composite Mo ₂ - molybdenumdisulfide

MWCNT - Multi-walled Carbon nanotubes

O2 - Oxygen

OH - Hydroxyl

PA6 - Polyamide 6

PEEK - Polyetheretherketone

PI - Polyimide

PMC - Polymer Matrix Composite PTFE - Polytetrafluoroethylene

SiC - Silicon Carbide

SRFP - Short fiber reinforced polymer Tg - glass transition temperature

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xiii

TiO - Titanium Oxide

UHMWPE - Ultra high molecular weight polyethylene

�� - Frictional forces

�� - Normal load

� - Average roughness

µ - Coefficient of friction

GPa - Gigapascal

m/s - Meter per second

MPa - Megapascal

ºC - Degree Celcius

p - Pressure

Tg - Gass transition temperature

v - Velocity

Ws - Specific wears rates

Wt% - Weight Percent

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1 This chapter provides the background, problem statement, objective as well as scope of the study.

1.1 Background of study

“Tribology” was derived from the Greek word tribos which means rubbing. The

science of tribology is comprised from three factors, which are friction, wear and lubrication of materials. In the application perspective, it deals with interface between two or more bodies in relative motion such as bearing, gears, piston-cylinder assembly and etc. Friction is the resistance to motion that occurs whenever one solid body is in contact with another solid body (Brostow et al., 2010). The root of friction between two surfaces in relative motion is the key to finding answer to the ever-increasing problems of huge financial losses due to wear and friction (Chand et al., 2008). The wear represents a surface damage or removal of material from one or both side of solid surface that are in contact during motion. The irregularity of the surface is the reason of wear occurs and would result in dimensional changes of the component and causes damage to the surface.

Nowadays, advanced materials such as polymer matrix composite (PMC), metal matrix composite (MMC) ceramic matrix composite (CMC) and carbon-carbon composite comprise the four main groups of tribo-materials. Among these materials, PMC have showed immerse potential because of their self lubrication properties, lightweight and resistance to wear, corrosion and organic solvent (Thomas et al.,

INTRODUCTION

CHAPTER 1

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2 2007). The promising phenomena when polymers slide against metal counterface, is the formation of transfer film. Bahadur et al. (1999) mentioned that the role of transfer film in polymer-metal sliding contact has long been realized as being responsible for the gradual transition from a transient wear behaviour to steady state wear behaviour. Also, it is widely believed that transfer films provide shielding of the soft polymer surface from the hard metal asperities. As most polymers are self-lubricating materials, the transfer film of polymer can act as a lubricant so that the coefficient of friction is much lower.

For polymers that posses high specific wear rates in the unreinforced condition, incorporation of almost any type of reinforcing fibers would result in significant reduction in wear and improve mechanical properties (Chand et al., 2008). The commonly used synthetic fibers such as glass, carbon, graphite and aramid are available as short, long fiber or fabric for reinforcement in thermoset as well as thermoplastic. Among the numerous fibers used for PMC, Kim et al. (2011) reported that glass fiber-reinforced PMC shows good tribological properties due to the superb bond strength with the matrix, but it may cause damage the counter surface by abrasion. The presence of continuous fiber reinforcement in plastic shows higher wear resistance than that of short fiber reinforced polymer. The fact is that higher length-to-fiber ratio results in more contact load transfer from matrix to fiber (Stachowiak, 2006; Chand et al., 2008). However, short fiber reinforced polymer are more favoured because of the potential for easy, cost effective and rapid moldability (Bahadur et al., 1990)

On the other hand, effect of particulate reinforcement or fillers such as oxide copper (CuO), sulfide copper (CuS), fluoride copper (CuF), silicon carbide (SiC), titanium oxide (TiO) are also well-known to enhance mechanical and tribological properties of polymer composite (Chang et al., 2010). The improvement of wear resistance due to either enhancement of modulus and hardness of materials or improved bonding between transfer film and metallic counterpart. Apart from that, when inoganic particles are used to combination with functional fillers such as polytetrafluoroethylene (PTFE), short-glass ,aramid and carbon fiber polymer with high wear resistance can be obtained (Stachowiak, 2006; Chand et al., 2008).

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3 Recently it was found that the contact surface was reduced with the presence of nanoparticles, in such a way that stress concentration on the individual fiber was minimized with dispersed nano-filler in contact region which consequently protected the polymer matrix in the interfacial region from the thermal mechanical failure (Stachowiak, 2006).

The major drawback of using synthetic fiber in tribo materials is about the environmental issue. The production of synthetic composite requires huge energy consumption and the environmental quality has suffered because of the pollution generated during the production and recycling of these synthetic fibers (Kalia et al., 2009). At present, the interest in using natural fibers (such as flax, hemp, jute, sisal, kenaf, flax and coir) as reinforcement for polymeric composite has increased due to their lightweight, renewability, low density, high specific strength, non abrasivity, combustibility, non toxicity, low cost and biodegrability (Aji et al., 2009). However, challenges in utilizing natural fiber as reinforcement is the lack of interfacial adhesion between the matrix and fibers due to the hydrophilicity of natural fiber (Yousif et al., 2012)

Therefore, Chand et al. (2008) have conducted a study on the effect of chemical treatment (silane) of sisal fiber on the tribological behavior of the sisal/polyester composite and concluded that treated sisal fiber/polyester composite have greater specific wear rates that untreated sisal fiber/polyester composite. The poor bonding between untreated fiber and matrix resulted in ease of fiber pull out and fiber debonding during dry sliding with metallic counterface. As review by Chin et al. (2009) they found that the kenaf fiber has a strong interfacial adhesion with polymers and thus it is superior than other natural fibers such as oil palm, sugarcane and jute. Besides, it is said that the presence of kenaf fiber have improved wear performance of epoxy about 85% but varies with the sliding direction on the fiber orientation. Thus, natural fiber serves as an important potential as tribomaterials.

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1.2 Problem Statement

Recently many natural fibers have been studied in a view to ensure their optimum utilization in developing tribo-compsite. Kenaf fiber is the most promising natural fiber used as reinforcement in polymer matrix due to it good mechanical properties along with having economic and ecological advantages. Many research has been carried out to study what extend they satisfy the required specification for good natural fiber based-reinforced polymer composite for tribological application. The challenges of incorporating natural fiber into a polymer matrix is the lack of good interfacial adhesion between the two components which would affect the wear behavior of natural fiber composite. Other than that, the thermal stability of natural fiber composite imposes limitation in application at high temperature which causes degradation of the fiber organic structure. These limitations are highly concerned because materials subjected to wear would expose to the material removal process and accumulation of frictional heat at the counterface. Thus, incorporation of nanoparticulates such carbon nanotube (CNT) may serve to improve the interfacial properties and thermal stability of natural fiber composite as well as the wear behaviour. Furthermore, technique to fabricate this composite via vacuum casting has not been explored and it is a new venture to fabricate near-net shaped composite component. This technique may also serve an improvement of the mechanical and physical properties of end products.

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1.3 Objective

The objectives of this study are as follows:

1. To fabricate Carbon Nanotube (CNT)/ short kenaf fiber reinforced epoxy composite with different CNT loading via vacuum casting technique

2. To analyze a characteristic of composites in terms of physical, thermal, chemical and morphological properties.

3. To study wear behavior of CNT/ short kenaf fiber reinforced epoxy composite in term of specific wear rates and coefficient of friction via pin-on-disc wear test.

1.4 Scope

The scope of this study is mainly focusing on the wear behaviour of polymer composite of epoxy reinforced with kenaf fiber as micro filler and carbon nanotube as nano filler. The loading of short kenaf fiber is remained constant at 4 wt% while the loading for CNT varied at 0.1, 0.3 and 0.5 wt%. dispersion of CNT process is performed by ultrasonication while the vacuum casting technique is used to produce void-free composite samples. The study include characterization of molecular interaction among the constituents in the CNT and kenaf fiber, determination of physical properties, thermal behaviour of the composite, as well as tribological properties under dry sliding test of the composite. The wear test was carried out with the application of two different sliding velocities (i.e. 1 and 2 m/s), at a constant load of 40 N and constant sliding distance of 3.75 km. The topological characteristic of the composite after dry sliding wear test is also studied to examine the wear mechanism.

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6 A review on previous research work in various area which relevant to this research is presented in this chapter.

2.1 Tribology

“Tribology” is defined as the science and technology of interacting surface in relative

motion, having its origin in the Greek words tribos meaning rubbing. Its is a study of the friction, wear and lubrication of materials. Tribology is the science and technology of interacting surface in relative motion or more simply expressed the study of friction, wear and lubrication (Cziochos, 1986). In the application perspective, it deals with interface between two or more bodies in relative motion. In any machine there are lots of component parts that operate by rubbing together such as bearings, gears, cams and tappets, piston cylinder assembly, bushing and etc.

Friction is the resistance to motion that occurs whenever one solid body is contact with another solid body (Stachowiak et al., 2010). In human life, friction must be exists in order to make thing work such as during walking, holding an object, contact between tires and road need some friction to move and etc. Sometimes, it is desirable to have high friction as in the case of brakes or low friction to save energy. Respecting to the moving parts in such machine or engine, almost no friction is required because interaction between two interface cause friction and wear of material involves. Undesirable of wear mechanism need to be avoided thus, people use a lubricant to prevent such high friction which causes wear.

LITERATURE REVIEW

CHAPTER 2

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7 Suh (1986) as cited by Chand et al., (2008), wear is defined as the progressive loss material from the operating surface of body as result of relative motion at the surface. The wear would result the dimensional change and irregularities on the contact surface either both side or one side. The dimensional would affect the efficiency of the operating component. While some types of material removal are beneficial (cutting, grinding and polishing), wear of single component (e.g. a bearing in the main rotor of a helicopter) can lead to catastrophic failure (Tuszynski, 1995).

2.1.1 Classification of Wear

Material can be removed from a solid surface by melting or sublimation, by chemical dissolution, or physical separation of atoms from the surface Ludema, (1992). In the wear process, the amount of material removed is quite small which makes its difficult to detect wear by casual inspection. However, the changed in shape, like obsolescence and surface damage in some parts, becomes very obvious. Refers to Tuszynski (1995) and Chand et al. (2008), the common forms of wear are defined as follows:

i. Abrasive wear: Abrasive wear occur when a hard, solid particle or asperity comes in contact with a softer surface. The softer surface experience both material loss and deformation of the remaining portion.

ii. Adhesion wear: Adhesive wear occurs when surface in contact bond together through local welding of asperities or cohesive bonding. If the bonded junction are stronger than one of the solid, wear arise from a shearing process within the solid

iii. Fatigue wear: Fatigue wear is a result of periodic stress variation between wearing surfaces. Even though the forces may be less than that required to permanently deform the material, local fatigue produces cracks that eventually lead to removal of relatively large pieces of material in the form of pitting, spalling or flaking

iv. Chemical or corrosive wear: This type of wear is found when chemical reaction occurs along with mechanical wear. This form of wear may lead to a

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4 1.2 Problem Statement

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5 1.3 Objective

The objectives of this study are as follows:

1. To fabricate Carbon Nanotube (CNT)/ short kenaf fiber reinforced epoxy composite with different CNT loading via vacuum casting technique

2. To analyze a characteristic of composites in terms of physical, thermal, chemical and morphological properties.

3. To study wear behavior of CNT/ short kenaf fiber reinforced epoxy composite in term of specific wear rates and coefficient of friction via pin-on-disc wear test.

1.4 Scope

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6 A review on previous research work in various area which relevant to this research is presented in this chapter.

2.1 Tribology

“Tribology” is defined as the science and technology of interacting surface in relative motion, having its origin in the Greek words tribos meaning rubbing. Its is a study of the friction, wear and lubrication of materials. Tribology is the science and technology of interacting surface in relative motion or more simply expressed the study of friction, wear and lubrication (Cziochos, 1986). In the application perspective, it deals with interface between two or more bodies in relative motion. In any machine there are lots of component parts that operate by rubbing together such as bearings, gears, cams and tappets, piston cylinder assembly, bushing and etc.

LITERATURE REVIEW

CHAPTER 2

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2.1.1 Classification of Wear

iv. Chemical or corrosive wear: This type of wear is found when chemical reaction occurs along with mechanical wear. This form of wear may lead to a

Wear Behavior of Carbon Nanotube (CNT)Short Natural Fiber Reinforced Epoxy Composite.

UNIVERSITI TEKNIKAL MALAYSIA MELAKA