ABSTRACT
Fiber-reinforced polymer composites have played a dominant role for a long time in a variety of applications for their high specific strength and modulus. The fiber which serves as a reinforcement in reinforced plastics may be synthetic or natural. This research focuses on natural plant and animal fibres (palm kernel, locust bean husk, goat fur and sheep wool). It deals with the production and characterization of composites of these fibres reinforced with recycled high density polyethylene. The physical properties such as density, water absorption and thickness swelling were determined. The tensile strength, flexural strength, hardness, impact energy, and wear properties were investigated. Thermal, chemical and microstructural analyses were also carried-out on the developed samples. The study revealed the result of the variation of the engineering properties with %wt composition of fibre reinforcements. It also presented the effect of variation of fibre length on engineering properties showing 10 mm as the critical length of fibres. The thermal analysis showed the destruction temperature range of the composites to lie between 400 and 500
TABLE OF CONTENTS
Title Page i
Declaration ii
Certification iii
Dedication iv
Acknowledgements v
Abstract vi
Table of Contents vii
List of Figures xi
List of Tables xiv
List of Plates xvii
List of Appendices xix
Nomenclature xx
CHAPTER ONE
1.0 Introduction 1
1.1 Background of the study 1
1.2 Problem Statement 2
1.3 The Present work 3
1.4 Aim and Objectives of the work 3
1.5 Scope of the study 4
1.6 Significance of the study 4
CHAPTER TWO
2.0 Literature Review 5
2.1 Introduction 5
2.2 Composite Materials 5
2.3 Types of Composite Materials 7
2.4 Properties of Composite Materials 8
2.4.1 Strength 8
2.4.2 Hardness 8
2.4.3 Stiffness 9
2.4.4 Toughness 9
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2.5 Classification of Composite Materials 9
2.5.1 Polymer Matrix Composites (PMCs) 9
2.5.1.1 Types of Polymer Reinforcement 10
2.5.2 Polymer Matrix Composite Materials 12
2.5.2.1 Properties of Polymer Matrix Materials 13
2.5.3 Metal Matrix Composites 13
2.5.4 Ceramic Matrix Composites 13
2.6 Natural Reinforcement Materials 13
2.7 Classification of Natural Fibers 14
2.7.1 Animal Fibers 15
2.7.2 Mineral Fibers 16
2.7.3 Plant Fibers 16
2.8 Applications of Natural Filler Composites 17
2.9 Advantages of Natural Filler Composites 18
2.10 Review of Past Works 19
CHAPTER THREE
3.0 Materials and Methods 22
3.1 Introduction 22
3.2 Materials 22
3.3 Equipment 22
3.4 Methods 23
3.4.1 Preparation of Recycled High Density Polyethylene 23
3.4.2 Preparation of Palm Kernel Fiber 23
3.4.3 Preparation of Locust Bean Husk Fiber 23
3.4.4 Preparation of Sheep Wool/Goat Fur 24
3.4.5 Sample Preparation 25
3.5 Determination of Density 25
3.6 Thickness Swelling and Water Absorption 25
3.7 Tensile Test 26
3.8 Static Bending Test 26
3.9 Impact Energy Test 27
3.10 Hardness Test 27
3.11 Wear Test 27
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3.12 Thermal Properties 28
3.14 X-Ray Fluorescent Spectrometry 29
3.15 Micro-structural Analysis 29
CHAPTER FOUR
4.0 Results and Discussions 30
4.1 Results 30
4.1.1 Density 30
4.1.2 Water absorption 32
4.1.3 Thickness Swelling 34
4.1.4 Tensile Strength 36
4.1.5 Flexural Strength 38
4.1.6 Impact Strength 40
4.1.7 Hardness 42
4.1.8 Wear Rate 44
4.1.9 Thermal Properties 46
4.1.10 Scanning Electron Microstructures 48
4.2 Discussion of Results 55
4.2.1 Physical Properties 55
4.2.1.1 Density 55
4.2.1.2 Water Absorption and Thickness Swelling 55
4.2.2 Mechanical Properties 55
4.2.2.1 Tensile Strength 55
4.2.2.2 Flexural Strength 56
4.2.2.3 Impact Strength 57
4.2.2.4 Hardness 57
4.2.2.5 Wear 57
4.2.3 Thermal Analysis 58
4.2.4 X-Ray Fluorescent Analysis 59
4.2.5 Micro-structural Analysis 59
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CHAPTER FIVE
5.0 Conclusions and Recommendations 60
5.1 Conclusions 60
5.2 Recommendations 61
5.3 Contributions to knowledge 61
REFERENCES 63
CHAPTER ONE
1.0 INTRODUCTION
1.1 Background of the Study
Over the last thirty years, composite materials, plastics and ceramics have been the dominant emerging materials but it is noted that the volume of different compositions and the number of applications of composite materials have been growing steadily, penetrating and conquering world markets relentlessly. Modern composite materials constitute a significant proportion of newly fabricated products ranging from domestic products to sophisticated products (Prakash, 2009; Hull, 1996).
Efforts to produce economical and attractive composite components have resulted in several innovative manufacturing techniques currently used in the composites industry. It is obvious, especially for composites, that the improvement in manufacturing technology alone is not enough to overcome the cost hurdle. It is essential that there be an integrated effort in design, materials processing, tooling, quality assurance, manufacturing, and even program management for composites to become competitive with metals. The use of composites has not been limited to aircraft industries but to other commercial applications in recent years. This is possible due to the introduction of new polymer resin matrix materials and high performance reinforcement fibers (Nayak, 2009; Prakash, 2009).
Natural fiber composites are emerging as realistic alternatives to glass-reinforced composites in many applications. Natural fiber composites such as hemp fiber-epoxy, flax fiber-polypropylene (PP), and china reed fiber-PP are particularly attractive in automotive applications because of lower cost and lower density. Glass fibers used for composites have density of 2.6 g/cm3 and cost between $1.30 and $2.00/kg. In comparison, flax fibers have a
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density of 1.5 g/cm3 and cost between $0.22 and $1.10/kg (Joshi et al, 2004). While, natural fibers traditionally have been used to fill and reinforce thermosets, natural fiber reinforced thermoplastics, especially polypropylene composites, have attracted greater attention due to their added advantage of recyclability (Joshi et al, 2004). Natural fiber composites are also claimed to offer environmental advantages such as reduced dependence on non-renewable energy/material sources, lower pollutant emissions, lower greenhouse gas emissions, enhanced energy recovery, and end of life biodegradability of components.
As industry attempts to lessen the dependence on petroleum based fuels and products there is an increasing need to investigate more environmentally friendly, sustainable materials to replace the existing glass fiber and carbon fiber reinforced materials (Zampaloni et al, 2007). Therefore, attention has recently shifted to the fabrication and properties of natural fiber reinforced materials. The automotive and aerospace industries have both demonstrated an interest in using more natural fiber reinforced composites, for example, in order to reduce vehicle weight, automotive companies have already shifted from steel to aluminum and now are shifting from aluminum to fiber reinforced composites for some applications.
This has led to predictions that in the near future plastics and polymer composites will comprise approximately 15% of total automobile weight (Mohanty et al, 2002; Zampaloni et al, 2007). In this work, some natural fibers were utilized as reinforcement with HDPE waste using physico-mechanical and thermal property as criteria.
1.2 Problem Statement
Natural fibre reinforced polymer composites have raised great interest among material scientists and engineers in recent years due to the need for developing environmentally friendly materials, and partly replacing currently used glass fibers for composite reinforcement. Glass fibres are widely used to reinforce plastics due to their low cost and
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fairly good mechanical properties. However, these fibres have serious drawbacks with respect to health and safety during handling and processing of fibre products. They can cause acute irritation of the skin, eyes and the upper respiratory tract. Concerns have been raised for long-term development of lung scarring (i.e., pulmonary fibrosis) and cancer. When released, glass fiber does not degrade and results in environmental pollution and threatens animal life and nature significantly (Neeraj and Geeta, 2013; Wambua et al., 2003).
1.3 The Present Work
It is against this backdrop (the stated problem) that the present research has developed and characterized recycled high density polyethylene (RHDPE)/Natural fiber composites: an alternative to conventional glass fiber reinforced composites.
1.4 Aim and Objectives
The aim of the present research is centered on the development and characterization of composites from recycled high density polyethylene (RHDPE) reinforced with plant fibre (locust bean husk and palm kernel) and animal fibre (sheep wool and goat fur). To achieve this aim, the following specific objectives are necessary:
i. To study the composition of the plant and animal fibres: palm kernel, locust bean husk, goat fur and sheep wool).
ii. To develop the composites using the polymer-fibre mix for each of the natural fibres.
iii. To study the mechanical and physical properties (tensile strength, flexural strength, hardness, impact energy, wear resistance, density, thickness swelling and water absorption) of the developed composites.
iv. To determine the effect of fibre length on the physical and mechanical properties of the developed composites
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v. To study the microstructure of the composites using scanning electron microscope (SEM)
vi. To study the thermal properties of the developed composites.
1.5 Scope of the Study
The scope of this present research will be limited to the following areas:
i. Preparing the natural fibres and RHDPE prior to compounding.
ii. Formulation by varying the fibre amounts (5-25 wt %).
iii. Development of the composite by the compounding and heat pressing method.
iv. Testing the physical and mechanical properties of the developed composite.
v. Microstructural analysis of the developed composites.
vi. Thermal analysis of the developed composites.
vii. Comparative analysis of the natural fibers (plant and animal).
1.6 Significance of the Research
The new paradigm in the preparation of fiber reinforced composites is the use of natural fibers in place of petroleum-based synthetic fibers. Even though glass-fiber-reinforced composites have good mechanical properties, they exhibit shortcomings such as higher density, difficulty to machine, and poor recycling properties. Natural fibers have special advantages such as low cost, low energy consumption, low density, high specific mechanical properties, and non-abrasive and biodegradable properties when compared to synthetic fibers like glass. The use of natural fibers to make low cost and eco-friendly composite materials is a subject of green importance.
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