Modelling And Characterization Of Stone Wool Fibre Reinforced High Density Polyethylene Composites.
Master of Science in Manufacturing Engineering
Faculty of Manufacturing Engineering
MODELLING AND CHARACTERIZATION OF STONE WOOL
FIBRE REINFORCED HIGH DENSITY POLYETHYLENE
COMPOSITES
Leong Shu Teng
(2)
MODELLING AND CHARACTERIZATION OF STONE WOOL FIBRE REINFORCED HIGH DENSITY POLYETHYLENE COMPOSITES
LEONG SHU TENG
A thesis submitted
in fulfillment of the requirements for the degree ofMaster of Science in Manufacturing Engineering
Faculty of Manufacturing Engineering
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
(3)
DECLARATION
I declare that this thesis entitled “Modelling and Characterization of Stone Wool Fibre Reinforced High Density Polyethylene Composites” is the result of my own research except as cited in the references. The thesis has not been accepted for any degree and is concurrently submitted in candidature of any other degree.
Signature : ……… Name : Leong Shu Teng Date
: 14/7/2016
(4)
APPROVAL
I hereby declare that I have read this thesis and in my opinion this thesis is sufficient in terms of scope and quality for the award for the award of Master of Science in Manufacturing Engineering.
Signature : ………..
Supervisor Name : Prof. Ir. Dr. Sivarao Subramonian Date
: 14/7/2016
(5)
DEDICATION
This thesis is dedicated to my beloved father, siblings and boyfriend. Thanks for always being there for me. Without their love and support this thesis would not have been made
(6)
ABSTRACT
Composites are a combination of two or more constituent materials that consist of phases like reinforcement and matrix phase. Polymer matrix composites consist of long or short fibres in a polymer matrix. Most polymer composites have been created to optimize the mechanical properties and are designed to be lighter and stronger to use in variety of applications such as automotive industry, sports equipments, aircraft components and etc. This research investigates the mechanical properties of stone wool (SW) fiber-reinforced high density polyethylene (HDPE) composites at fiber loadings, 0 to 60 wt.% through two methods: experimental and finite element analysis. Nowadays, due to the increase in environmental awareness, the wide spread use of glass, carbon and aramid has greatly decreased due to greater weight, higher cost and adverse environmental impact brought by those fibres. Research into new fibres has significantly increased, making stone wool among the chosen fibres. Stone wool is a natural material that is formed from one earth’s most abundant material. It becomes a mass of fine, intertwined fibres with a typical diameter of 6 to 10 micrometres after an advanced process. SW shows few good characteristics such as a good insulator, lightweight, good quality, sustainable and also environmentally friendly. It also has proven to be a safer option to be used than carbon and glass fibre. The stone wool polymer composites (SWPC) specimens were prepared using the hot compression molding process. These samples were then prepared and tested according to ASTM standards for tensile, flexural and hardness test. Scanning electron microscopy (SEM) was carried out on the fractured surface to observe the interaction between matrix and fiber in the composites. The experimental results revealed that there was an increase in fiber loading which also increases the mechanical properties of the material. Significant improvement of mechanical properties is observed and recorded for 20wt.% SWPC. The results also shows a significant decrease in tensile and flexural properties after 40wt.% SWPC. The hardness test results shows that it improves with the increase of the fibre weight percentage and the value maintained after 40wt.% SWPC. To reveal the actual phenomenon of the composites, finite element modelling and analysis has also been performed. The mechanical properties was predicted using the model developed by ANSYS. The model was then experimentally validated. The model outputs were found to have excellent agreement with the experimental results, with an accuracy of more than 90% for tensile and 85% for flexural test. The accuracy of established ANSYS model proving its robustness and expected to reduce the industrial experimental cost holistically.
(7)
ABSTRAK
Komposit adalah gabungan dua atau lebih bahan konstituen yang terdiri daripada fasa pengukuhan dan fasa matriks. Komposit matriks polimer terdiri daripada gentian panjang atau pendek dalam matriks polimer. Kebanyakan komposit matriks telah dibuatkan untuk mengoptimumkan sifat-sifat mekanik dan direka untuk menjadi lebih ringan dan lebih kuat untuk digunakan dalam pelbagai aplikasi seperti industri automotif, peralatan sukan, komponen pesawat dan lain-lain. Penyelidikan ini menyiasatkan sifat mekanikal tentang Polietilena berketumpatan tinggi (HDPE) yang diperkukuhkan dengan campuran batu kapas (SW) dalam komposisi 0- 60wt.% dengan menggunakan dua cara: eksperimen dan analisis unsur terhingga (FEA). Pada masa kini, disebabkan peningkatan kesedaran terhadap alam sekitar, penyebaran penggunaan serat kaca, karbon dan aramid sebagai pengisi telah dikurangkan disebabkan impak dan kesan buruk yang dibawa terhadap alam sekitar, isipadu yang berat dan kos yang tinggi. Penyelidikan untuk gentian yang baru amat diperlukan. Oleh itu, SW dipilih sebagai gentian baru yang akan dikaji. SW merupakan sebuah bahan asli yang dihasilkan daripada tanah dan ia merupakan bahan yang paling senang didapati. Ia menjadi benda yang halus dan mempunyai diameter sebanyak 6 hingga 10 mikrometer selepas mengalami pemprosesan yang lebih tinggi. SW mempunyai sifat yang amat bagus seperti penebat, ringan, kualiti tinggi, mampan dan mesra kepada alam sekitar. Ia juga telah terbukti menjadi pilihan yang lebih selamat digunakan daripada gentian karbon dan kaca. SWPC specimen telah disediakan dengan menggunakan pengacuan mampatan panas. Sampel-sampel ini kemudian disediakan dan diuji mengikuti piawaian ASTM untuk ujian tegangan, lenturan dan kekerasan. Kemikroscopan electron imbasan (SEM) telah dijalankan ke atas permukaan yang retak untuk melihat interaksi antara matriks dan gentian dalam komposit. Keputusan eksperimen menunjukkan bahawa semakin meningkat komposisi gentian, semakin meningkat sifat mekanikal komposit tersebut. Peningkatan sifat mekanikal yang ketara boleh diperhatikan dan direkodkan oleh 20wt.% komposit manakala penurunan yang ketara bagi sifat tegangan dan lenturan berlaku selepas 40wt.% komposit. Kekerasan komposit meningkat dengan penambahan komposisi gentian SW ke dalam HDPE. Untuk lebih memahami fenomena sebenar pada komposit, FEA model dan analisis telah dilaksanakan. Model yang dibangunkan oleh ANSYS telah digunakan untuk meramalkan sifat-sifat mekanikal di mana model itu kemudian disahkan dengan keputusan yang diperolehi daripada eksperimen. Keluaran model didapati mempunyai persetujuan yang amat baik dengan keputusan eksperimen, dengan ketepatan yang lebih daripada 90% bagi ujian tegangan dan 85% bagi ujian lenturan. Ketepatan model ANSYS yang ditubuhkan telah membuktikan kekukuhannya dan dijangka akan mengurangkan kos eksperimen perindustrian secara holistik.
(8)
ACKNOWLEDGEMENTS
First and foremost, I would like to take this opportunity to express my sincere acknowledgement to my supervisor, Professor Ir. Dr. Sivarao Subramonian and my co-supervisor, Professor Qumrul Ahsan for their fully support and efforts to guide and give advice along the period of this master research.
My special thanks to Zamalah scholarship which succeeded the completion of this research. I would like to specially thank the top level management of the Universiti Teknikal Malaysia Melaka, Centre for research and Innovation Management and Faculty of Manufacturing Engineering for providing continuous technical and moral support.
Not to forget, thanks to the lab technicians involved from Faculty of Manufacturing Engineering for assisting and sharing their skills, opinions, advices and guidance in handling the equipments throughout the research.
Besides that, thanks to everyone that have been involved officially or unofficially and act as crucial parts of my realization of this research. Last but not least, I would like to say a big thank you to my peers and beloved family for their fully support and encouragement which has motivate me to complete and make this research a success.
(9)
TABLE OF CONTENTS PAGE DECLARATION APPROVAL DEDICATION ABSTRACT i ABSTRAK ii ACKNOWLEDGEMENTS iii
TABLE OF CONTENTS iv
LIST OF TABLES vii
LIST OF FIGURES ix
LIST OF APPENDICES xiv
LIST OF ABBREVIATIONS xv
LIST OF PUBLICATIONS xvii
CHAPTER
1. INTRODUCTION 1
1.1 Background 1
1.2 Problem Statement 4
1.3 Objectives 6
1.4 Scope 6
1.5 Thesis Organization 7
2. LITERATURE REVIEW 8
2.1 Introduction 8
2.2 Composites 8
2.2.1 Metal Matrix Composite (MMC) 11
2.2.2 Ceramic Matrix Composite (CMC) 12
2.2.3 Polymer Matrix Composite (PMC) 12
2.2.3.1 Natural Fibre Reinforced Polymer Composites 13
2.3 Filler 14
2.3.1 Types of Reinforcement 17
2.3.2 Organic Fibre Reinforced Polymer Composites 18
2.3.3 Inorganic Fibre Reinforced Polymer Composites 23
2.3.4 Stone Wool 27
2.4 Matrices 30
2.4.1 Functions of the Matrix in Composites 31
2.4.2 Thermoset 32
2.4.3 Thermoplastic 32
2.4.3.1 Polyethylene 33
2.5 Finite Element Analysis (FEA) 36
2.5.1 Analysis System (ANSYS) 38
(10)
3. METHODOLOGY 43
3.1 Introduction 43
3.2 Preliminary Investigations 45
3.2.1 Materials Selection 45
3.2.2.1 Matrix 45
3.2.2.2 Filler 46
3.2.3 Experimental Matrix 47
3.3 Processing of Composites 48
3.3.1 Filler Characterization 48
3.3.2 Polymer and Filler Treatment 50
3.3.2.1 Treatment for Polymer 50
3.3.2.2 Treatment for Filler 51
3.3.3 Compounding 53
3.3.4 Hot Compression Molding 54
3.3.5 Specimentation 56
3.4 Preliminary Experimental 57
3.5 Finite Element Modelling 57
3.5.1 Pre-Processing 58
3.5.2 Analysis 62
3.5.2.1 Formulation 64
3.5.3 Post-Processing 68
3.6 Mechanical Tests 69
3.6.1 Tensile Test 70
3.6.2 Flexural Test 72
3.6.3 Shore Hardness Test 74
3.7 Morphology Observation 76
3.8 Model Validation 77
3.9 Summary 77
4. RESULTS AND DISCUSSION 78
4.1 Introduction 78
4.2 Results of Modelling 78
4.2.1 Tensile Test 79
4.2.2 Flexural Test 82
4.3 Characterization of Composites 86
4.3.1 Tensile Properties 87
4.3.1.1 Yield Strength 89
4.3.1.2 Tensile Strength 90
4.3.1.3 Tensile Modulus 92
4.3.1.4 Ductility 94
4.3.1.5 Morphology Observation of Tensile Fracture Surface 95
a) 20wt% Stone Wool Reinforced HDPE 95
b) 60wt% Stone Wool Reinforced HDPE 97
4.3.1.6 Summary of Finding in Tensile Properties 98
4.3.2 Flexural Properties 101
4.3.2.1 Flexural Strength 103
4.3.2.2 Flexural Strain 104
(11)
4.3.2.4 Morphology Observation of Flexural Fracture Surface 107
a) 20wt% Stone Wool Reinforced HDPE 107
b) 40wt% Stone Wool Reinforced HDPE 108
c) 60wt% Stone Wool Reinforced HDPE 109
4.3.2.5 Summary of Finding in Flexural Properties 110
4.3.3 Hardness Properties 113
4.4 Model Validation 115
4.4.1 Distance between Fibre 115
4.4.2 Tensile Test 118
4.4.3 Flexural Test 121
4.5 Summary 124
5. CONCLUSION AND RECOMMENDATIONS FOR 126
FUTURE RESEARCH 5.1 Conclusion 126
5.2 Recommendations 128
5.2.1 Propose Products 128
5.2.2 Future Research 130
REFERENCES 132
APPENDICES 145
(12)
LIST OF TABLES
TABLE TITLE PAGE
2.1 Types of Fibres 16
2.2 Physical Properties of LDPE 35
2.3 Physical Properties of HDPE 36
3.1 Composition of Stone Wool 47
3.2 Dimensions of Standard Specimens 47
3.3 Parameters for Compounding Process 54 3.4 Parameters for Hot Compression Moulding 56 3.5 Input Value Material Properties of Model Composites Material 60
3.6 Parameters for Tensile Test 71
3.7 Parameters for Flexural Test 73
4.1 Analysis Tensile Properties 82
4.2 Analysis Flexural Properties 86
4.3 Tensile Properties 88
4.4 Flexural Properties 102
4.5 Result of Shore Hardness Test 113
4.6 Measurement of Distance between Fibres of each Composition 116 4.7 Experimental and Projection Values of Distance between Fibres for 117
(13)
4.8 Comparison of Experimental and ANSYS Analysis 120 Tensile Modulus and Error Percentage
4.9 Comparison of Experimental and ANSYS Analysis 123 Flexural Modulus and Error Percentage
(14)
LIST OF FIGURES
FIGURES TITLE PAGE
2.1 Classifications of Composites Material System 9
2.2 Stone Wool Production Process 28
2.3 Structure of Thermoplastic 33
2.4 Polyethylene Macromolecule Carbon Chain 34
2.5 Structure of LDPE 35
2.6 Structure of HDPE 36
3.1 Methodology Flow Chart 44
3.2 Gold Coated Stone Wool Filler 49
3.3 Length Measurement of Stone Wool Fibre by SEM 49
3.4 SEM Image of Diameter Measurement of Stone Wool Fibre 50
3.5 Treatment for HDPE 51
3.6 Cleaning Process by Ultrasonic Cleaner 52
3.7 Dried Stone Wool Filler 52
3.8 Haake Polymer Lab OS Rheodrive 16 internal mixer 53
3.9 Compounded Material 54
3.10 Hot Compression Moulding Machine 56
(15)
3.12 Finite Element Model of (a) Pure HDPE, (b) Meshed Material and 60 (c) Stone Wool Reinforced Composites
3.13 Boundary Condition of the Finite Element Model 62 3.14 Flow Chart of Model Validation 63 3.15 Deformed Shape for Finite Element Model after (a) Tensile test and 69
(b) Flexural test
3.16 Nodal Solution of Finite Element Model for (a) Tensile test and 69 (b) Flexural test
3.17 Universal Testing Machine (Shimadzu AG-1 100KN, Japan) 71 3.18 ASTM D7264 Procedure A Flexural Test Standard 73 3.19 Durometer (CV Instruments Europe BV) 75 3.20 Scanning Electron Microscopy 76 4.1 Deformed Shape for Finite Element Model after Tensile Testing 80 4.2 Nodal Solution of Tensile Test for Pure HDPE (a) Maximum Stress 80
and (b) Maximum Strain
4.3 Nodal Solution of Tensile Test for 20wt.% Reinforced HDPE 81 Composite (a) Maximum stress and (b) Maximum strain
4.4 Results Tensile Modulus from Finite Element Analysis 82 4.5 Deformed Shape for Finite Element Model after Flexural Testing 83 4.6 Nodal Solution of Flexural Test for Pure HDPE (a) Maximum stress 84
and (b) Maximum strain
4.7 Nodal Solution of Flexural Test for 40wt.% Reinforced HDPE 85 Composite (a) Maximum stress and (b) Maximum strain
4.8 Results Flexural Modulus from Finite Element Analysis 86 4.9 Stress-strain Curve for Tensile Test 87
(16)
4.10 Yield Strength vs. Filler Weight Percentage for 89 Stone Wool Reinforced HDPE Composites
4.11 Tensile Strength vs. Filler Weight Percentage for 92 Stone Wool Reinforced HDPE Composites
4.12 Tensile Modulus vs. Filler Weight Percentage for 93 Stone Wool Reinforced HDPE Composites
4.13 Percentage of Elongation vs. Filler Weight Percentage for 95 Stone Wool Reinforced HDPE Composites
4.14 (a) & (b) SEM Micrograph of Tensile Deformed 20wt.% 96 Stone Wool Reinforced HDPE
4.15 (a) & (b) SEM Micrograph of Tensile Deformed 60wt.% 97 Stone Wool Reinforced HDPE
4.16 Tensile Strength vs. Filler Weight Percentage for Stone Wool, 99 Bamboo, Coconut and Glass Fibres Reinforced Composites
4.17 Summary of Tensile Properties 100 4.18 Stress-strain Curve for Flexural Test 101 4.19 Flexural Strength vs. Filler Weight Percentage for 103
Stone Wool Reinforced HDPE Composites
4.20 Flexural Strain vs. Filler Weight Percentage for 105 Stone Wool Reinforced HDPE Composites
4.21 Flexural Modulus vs. Filler Weight Percentage for 106 Stone Wool Reinforced HDPE Composites
4.22 SEM Micrograph of Flexural Deformed 10wt.% Stone Wool 107 Reinforced HDPE
(17)
4.23 SEM Micrograph of Flexural Deformed 40wt.% Stone Wool 108 Reinforced HDPE
4.24 SEM Micrograph of Flexural Deformed 60wt.% Stone Wool 109 Reinforced HDPE
4.25 Tensile Strength vs. Filler Weight Percentage for Stone Wool, 111 Bamboo, Coconut and Glass Fibres Reinforced Composites
4.26 Summary of Flexural Properties 112 4.27 Shore D Hardness Value vs. Filler Weight Percentage for 114
Stone Wool Reinforced HDPE Composites
4.28 Shore D Hardness value vs. Filler Weight Percentage for 114 Stone Wool, Bamboo, Coconut and Glass Fibres Reinforced
Composites
4.29 Distance Measurement between Fibres by SEM 116 4.30 Graph of Distance between Fibres vs. Filler Weight Percentage 117 4.31 Comparison Point of Failure between 119
Experimental Specimen and Established Model (a) Pure HDPE and (b) Stone Wool Reinforced Composites
4.32 Comparison of Experimental and ANSYS Analysis 120 Tensile Modulus
4.33 Comparison Point of Failure between Experimental Specimen and 122 Model (a) Pure HDPE and (b) Stone Wool Reinforced Composites
4.34 Comparison of Experimental and ANSYS Analysis 123 Flexural Modulus
(18)
5.2 Underlayment and Subfloor 129
(19)
LIST OF APPENDICES
APPENDIX TITLE PAGE
A Stress-strain Curve for Tensile Test 146
B Stress-strain Curve for Flexural Test 154
(20)
LIST OF ABBREVIATIONS
Al2O3 - Alumina
APDL - ANSYS Parametric Design Language ANSYS - Analysis System
ASTM - American Society for Testing and Materials
AWPEX - Apatite-Wollastonite Particulate Reinforced Polyethylene BN - Boron Nitride
CaCO3 - Calcium Carbonate
CF - Carbon Fibre
CMC - Ceramic Matrix Composites
CTDIC - Cardinal Derivative of Toluene Diisocyanate
EL - Elongation
Fe - Ferum
FEA - Finite Element Analysis
FKP - Faculty of Manufacturing Engineering FRC - Fibre Reinforced Composite
FRP - Fiber Reinforced Polymer GF - Glass Fibre
GPa - Giga Pascal
(21)
HDPE-r - Recycled High Density Polyethylene LDPE - Low Density Polyethylene
MMC - Metal Matrix Composites MPa - Mega Pascal
NaOH - Sodium Hydroxide PE - Polyethylene
PEMA - Polyethylene Grafted with Maleic Anhydride PMC - Polymer Matrix Composites
rpm - Revolutions per minute SEM - Scanning Electron Microscope SFFT - Single Fibre Fragmentation Test SRPE - Sand Reinforced Polyethylene
SS - Sago Starch
SWPC - Stone Wool Polymer Composites
SWRHDPEC - Stone Wool Reinforced High Density Polyethylene Composites TCP/HDPE - Tri-Calcium Phosphate-High Density Polyethylene
(22)
LIST OF PUBLICATIONS
1. Sivaraos, Leong, S. T., Yusof, Y. and Tan, C. F., 2015. An Experimental and Numerical Investigation of Tensile Properties of Stone Wool Fiber Reinforced Polymer Composites. Advanced Materials Letters, 6(10), pp. 888-894. (SCOPUS Indexed)
2. Sivarao, Aidy Ali and Leong, S. T., 2014. Enhanced Tensile Properties of Stone Wool Fiber-Reinforced High Density Polyethylene Composites.
(23)
CHAPTER 1
INTRODUCTION
1.1 Background
Composites are a material made from two or more constituent materials with different chemical and physical properties. When constituent materials are combined, a composite material, which has characteristics different from the individual components, is produced. Examples of typical engineering composite materials are polymer matrix composites (PMC), metal matrix composites (MMC) and ceramic matrix composites (CMC). The polymer matrix in a polymer matrix composite consists mainly of thermoset or thermoplastic resin.
According to Rassiah et al. (2011), polymer is a long chain of repeated atoms and produced by joining molecules, which are known as monomers. In other words, polymer is a high molecular weight compound consisting of many repeated small segments. The block results of a polymer are usually a result of the factual characteristics of a chemical reaction with the usage of the smallest building block. All of these blocks result in a polymer. Polymers can be made using two different methods, known as condensation and poly-addition. The main bonds that are being formed between the molecules are covalent bonds, which are very strong. These bonds are caused by the forces of Van der Waal (Callister and Rethwisch, 2007). They are able to produce branched or linear polymers. The molecules also have a tendency to form secondary bonds, which actually hold a magnitude of lower
(24)
Most composites have been created to optimize the mechanical properties and are designed to be stronger and lighter to apply through environments of high temperature and to resist corrosion. This is because reinforced fibres are the principal load-carrying constituents while matrix is the load transfer medium between them (Kaw, 2006). Thermoplastic composites which is reinforced with different types of fibres such as long, short and mat of natural and synthetic fibres like coconut, oil palm, hemp, glass, carbon , and etc. are used in a variety of applications such as in the automotive industry, sports equipments, aircraft structural components, ballistic, tires , and etc. They are used because of their improved properties such as stiffness, toughness, ambient and high temperature strength, creep resistance, and corrosion resistance (Chandra et al., 1999). Many researchers have investigated the mechanical properties of thermoplastic composites and discovered that there is improvement in its mechanical properties.
High density of polyethylene (HDPE) is a polymer that has a low degree of branching in a long chain of repeated atoms, thus having strong intermolecular force (Rassiah et al., 2011). Mineral fibres such as carbon fibre (CF) and glass fibres (GF) are widely used as reinforcement of polymer composites. Enhanced mechanical properties of mineral fibre reinforced HDPE composites have been observed and reported in many investigations. Huang et al. (2013) studied the effect of individual and combined GF on morphology and mechanical performance of HDPE composites. Mechanical properties of composites with combined GF fibres varied with GF ratio at a given total fibre loading level. The use of larger portion of GF in the mix can lead to better composites performance. Lopresto et al. (2011) investigated the mechanical characterisation of basalt fibre reinforced plastic. The results obtained showing a high performance of the basalt reinforced composites in terms of young modulus, compressive and bending strength.
(1)
LIST OF APPENDICES
APPENDIX TITLE PAGE
A Stress-strain Curve for Tensile Test 146
B Stress-strain Curve for Flexural Test 154
(2)
xv
LIST OF ABBREVIATIONS
Al2O3 - Alumina
APDL - ANSYS Parametric Design Language ANSYS - Analysis System
ASTM - American Society for Testing and Materials
AWPEX - Apatite-Wollastonite Particulate Reinforced Polyethylene
BN - Boron Nitride
CaCO3 - Calcium Carbonate
CF - Carbon Fibre
CMC - Ceramic Matrix Composites
CTDIC - Cardinal Derivative of Toluene Diisocyanate
EL - Elongation
Fe - Ferum
FEA - Finite Element Analysis
FKP - Faculty of Manufacturing Engineering FRC - Fibre Reinforced Composite
FRP - Fiber Reinforced Polymer
GF - Glass Fibre
GPa - Giga Pascal
(3)
HDPE-r - Recycled High Density Polyethylene LDPE - Low Density Polyethylene
MMC - Metal Matrix Composites MPa - Mega Pascal
NaOH - Sodium Hydroxide
PE - Polyethylene
PEMA - Polyethylene Grafted with Maleic Anhydride PMC - Polymer Matrix Composites
rpm - Revolutions per minute SEM - Scanning Electron Microscope SFFT - Single Fibre Fragmentation Test SRPE - Sand Reinforced Polyethylene
SS - Sago Starch
SWPC - Stone Wool Polymer Composites
SWRHDPEC - Stone Wool Reinforced High Density Polyethylene Composites TCP/HDPE - Tri-Calcium Phosphate-High Density Polyethylene
(4)
xvii
LIST OF PUBLICATIONS
1. Sivaraos, Leong, S. T., Yusof, Y. and Tan, C. F., 2015. An Experimental and Numerical Investigation of Tensile Properties of Stone Wool Fiber Reinforced Polymer Composites. Advanced Materials Letters, 6(10), pp. 888-894. (SCOPUS Indexed)
2. Sivarao, Aidy Ali and Leong, S. T., 2014. Enhanced Tensile Properties of Stone Wool Fiber-Reinforced High Density Polyethylene Composites.
(5)
CHAPTER 1
INTRODUCTION
1.1 Background
Composites are a material made from two or more constituent materials with different chemical and physical properties. When constituent materials are combined, a composite material, which has characteristics different from the individual components, is produced. Examples of typical engineering composite materials are polymer matrix composites (PMC), metal matrix composites (MMC) and ceramic matrix composites (CMC). The polymer matrix in a polymer matrix composite consists mainly of thermoset or thermoplastic resin.
According to Rassiah et al. (2011), polymer is a long chain of repeated atoms and produced by joining molecules, which are known as monomers. In other words, polymer is a high molecular weight compound consisting of many repeated small segments. The block results of a polymer are usually a result of the factual characteristics of a chemical reaction with the usage of the smallest building block. All of these blocks result in a polymer. Polymers can be made using two different methods, known as condensation and poly-addition. The main bonds that are being formed between the molecules are covalent bonds, which are very strong. These bonds are caused by the forces of Van der Waal (Callister and Rethwisch, 2007). They are able to produce branched or linear polymers. The molecules also have a tendency to form secondary bonds, which actually hold a magnitude of lower
(6)
2
Most composites have been created to optimize the mechanical properties and are designed to be stronger and lighter to apply through environments of high temperature and to resist corrosion. This is because reinforced fibres are the principal load-carrying constituents while matrix is the load transfer medium between them (Kaw, 2006). Thermoplastic composites which is reinforced with different types of fibres such as long, short and mat of natural and synthetic fibres like coconut, oil palm, hemp, glass, carbon , and etc. are used in a variety of applications such as in the automotive industry, sports equipments, aircraft structural components, ballistic, tires , and etc. They are used because of their improved properties such as stiffness, toughness, ambient and high temperature strength, creep resistance, and corrosion resistance (Chandra et al., 1999). Many researchers have investigated the mechanical properties of thermoplastic composites and discovered that there is improvement in its mechanical properties.
High density of polyethylene (HDPE) is a polymer that has a low degree of branching in a long chain of repeated atoms, thus having strong intermolecular force (Rassiah et al., 2011). Mineral fibres such as carbon fibre (CF) and glass fibres (GF) are widely used as reinforcement of polymer composites. Enhanced mechanical properties of mineral fibre reinforced HDPE composites have been observed and reported in many investigations. Huang et al. (2013) studied the effect of individual and combined GF on morphology and mechanical performance of HDPE composites. Mechanical properties of composites with combined GF fibres varied with GF ratio at a given total fibre loading level. The use of larger portion of GF in the mix can lead to better composites performance. Lopresto et al. (2011) investigated the mechanical characterisation of basalt fibre reinforced plastic. The results obtained showing a high performance of the basalt reinforced composites in terms of young modulus, compressive and bending strength.