ABSTRACT
This study is about the production and characterization of epoxy-rice husk
ash composite. Composites were produced at 10%,20%,30%,40% and 50%
volume fraction of Rice Husk Ash(RHA) fillers and the epoxy was cast neat at
0%RHA which served as the control .The microstructure of the composites were
studied with Scanning Electron Microscopy(SEM) and Energy Dispersive X-ray
Spectroscopy(EDX).Mechanical properties of the composites such as tensile
properties(tensile stress, tensile strain, Young’s modulus, tensile strength and
percentage elongation at fracture),compressive strength, toughness, flexural
strength and hardness were experimentally determined in the engineering
labouratory using hounsfield (monsanto) tensometer, charpy v-notch impact
testing machine, flexural testing machine and Rockwell hardness testing machine.
The Scanning Electron Microscopy (SEM) analysis showed that interfacial
interactions existed between the rice husk ash particles and the epoxy matrix.
Energy Dispersive X-ray Spectroscopy (EDX) analysis indicated that interfacial
reactions existed between the epoxy matrix and the rice husk ash particles
because the composites did not contain homogenous elements. However each of
the composites contained C,O,Si and Cl while the cast neat epoxy(control)
contained C,O and Cl. Results of the mechanical property tests showed low gain
in hardness, toughness, flexural strength and Young’s modulus. The tensile
properties showed: that at 40%RHA the highest tensile strength of 37.006MPa was
obtained, the cast neat epoxy (control 0%RHA) had the best Young’s modulus of
356.538MPa and percentage elongation at fracture improved from 1.3% to 2.0%
as volume fraction of rice husk ash increased from 0% to 10%,20%,30%,40% and
50%.Increasing the volume fraction of rice husk ash from 0% to 10%,
20%,30%,40% and 50% led to decrease of these mechanical properties: toughness
from 2.0J to 0.3J,hardness from 344hardness value to 144 hardness value and
flexural strength from 6.0Mpa to 1.50Mpa.There was significant improvement in
the compressive strength of the composites from 15.75MPa to 18.75MPa as the
volume fraction of rice husk ash increased from 0% to 10%,20%,30%,40% and
50%.It was deduced from the study that epoxy-rice husk ash composite is
suitable for engineering applications subjected to compression. Surface coating of
rice husk ash could be used to improve its adhesion to the epoxy matrix in order
to enhance the mechanical properties of the composites for other engineering
applications.
TABLE OF CONTENTS
Title Page – – – – – – – – – – i
Approval Page- – – – – – – – – ii
Certification – – – – – – – – – iii
Dedication – – – – – – – – – – iv
Acknowledgement – – – – – – – – – v
Abstract – – – – – – – – – vi
Table of Content – – – – – – – – vii
List of Figures – – – – – – – – x
List of Tables – – – – – – – – xiii
List of Plates – – – – – – – – – xv
CHAPTER ONE: INTRODUCTION
1.1 Background Information – – – – – – 1
1.2 Statement of the Problem – – – – – – 5
1.3 Objectives of the Study – – – – – – 6
1.4 Justification of the Study – – – – – – 7
1.5 Scope and Limitations of the Study – – – – – 7
CHAPTER TWO: LITERATURE REVIEW
2.1 Overview of Composites – – – – – – 9
2.2 Rice Husk Ash – – – – – – – – 14
2. 2.1 Industrial Applications of Rice Husk Ash – – – – 15
2.3 Epoxy – – – – – – – – – 16
2.3.1 Curing of Epoxy Resins – – – – – – 17
2.5.2 Engineering Applications of Epoxy – – – – 17
2.4 Compressive Strength – – – – – – 18
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2.5 Toughness – – – – – – – – 19
2.6 Flexural Strength – – – – – – – 19
2.7 Hardness – – – – – – – – 19
2.8 Tensile Properties – – – – – – – 20
2.8.1 Stress – – – – – – – – – 20
2.8.2 Strain – – – – – – – – – 20
2.8.3 Tensile Strength – – – – – – – 21
2.8.4 Young’s Modulus – – – – – – – 22
2.8.5 Elongation at Fracture – – – – – – 22
2.9 Scanning Electron Microscopy – – – – – 23
2.9.1 Components of a Scanning Electron Microscope – – 25
2.10 Energy Dispersive X-Ray Spectroscopy – – – – 26
2.10.1 Applications of Scanning Electron Microscopy – Energy Dispersive
X-Ray Spectroscopy Analysis – – – – – 29
2.11 Microstructure – – – – – – – – 30
2.12 Adhesion and Cohesion – – – – – – 31
2.13 Calculation of Fiber Volume Fraction – – – – 32
CHAPTER THREE: MATERIALS AND METHODS
3.1 Materials – – – – – – – – – 33
3.1.1 Matrix Material – – – – – – – 33
3.1.2 Filler Material – – – – – – – – 33
3.2.0 Methods – – – – – – – – 34
3.2.1 Preparation of Composite Mould – – – – – 34
3.2.2 Composite Fabrication – – – – – – 35
3.3 Mechanical Property Tests – – – – – – 37
3.3.1 Tensile Testing of Composite Samples – – – – 37
3.3.2 Compressive Strength Test – – – – – – 38
3.3.3 Toughness Test – – – – – – – 38
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3.3.4 Hardness Test – – – – – – – – 39
3.3.5 Flexural Strength Test – – – – – – 39
3.4 Scanning Electron Microscopy and Energy Dispersive X- Ray
Spectroscopy Analysis – – – – – 40
CHAPTER FOUR: RESULTS AND DISCUSSION
4.1 Results – – – – – – – – – 42
4.1a Results for Mechanical Properties – – – – – 43
4.1b Results of Scanning Electron Microscopy Analysis – – 53
4.1c Results of the Energy Dispersive X-Ray Spectroscopy Analysis 61
4.2 Discussion of Results – – – – – – – 70
4.2.1 Mechanical Properties – – – – – – 70
4.2.1a Tensile Properties – – – – – – – 70
4.2.1b Toughness – – – – – – — – 72
4.2.1c Hardness – – – – – – – – 73
4.2.1d Flexural Strength – – – – – – – 73
4.2.1e Compressive Strength – – – – – – 73
4.2.2 Scanning Electron Microscopy Analysis – – – – 74
4.2.3 Energy Dispersive X-Ray Spectroscopy Analysis – – 76
CHAPTER FIVE: CONCLUSION AND RECOMMENDATIONS
5.1 Conclusion – – – – – – – 78
5.2 Recommendations – – – – – – – 79
References – – – – – – – – – 80
Appendix I- – – – – – – – – – 85
Appendix II – – – – – – – – – 86
Appendix III – – – – – – – – – 87
Appendix IV – – – – – – – – – 88
Appendix V — – – – – – – – – 91
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CHAPTER ONE
INTRODUCTION
1.1 Background Information
Most times engineers are faced with the task of developing a new material that
has light weight, low cost and good mechanical properties. A promising option to
this task is to use a low density particulate material like rice husk ash in a polymer
matrix to form a polymer composite. Rice husk ash is a by-product of combustion
of rice husk at rice mills (Zemke and Woods, 2008). Researchers are currently
investigating the use of ash for composite production since ash is an abundant
agricultural waste, is renewable and has low bulk density. Rice husk ash had
been applied in other areas like manufacturing insulating powder, production of
refractory bricks, cement production and sandcrete block production. However
there are limited applications of rice husk ash in composite production.
A composite material is a microscopic or macroscopic combination of two
or more distinct materials with a recognizable interface between them. In a
composite material the constituents do not dissolve or merge completely in one
another. Normally the components in a composite material can be physically
identified and they exhibit interface between one another. A particulate composite
consists of a matrix reinforced with a dispersed phase in form of particles. Soft
particles like coir dust, rice husk flour, baggase ash, sawdust and rice husk ash can
be dispersed in a harder matrix to improve machinability and reduce coefficient of
friction (Lake,2002;Jiquao et al, 2010)
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One advantage of a composite is that two or more materials could be combined to
take advantage of the good characteristics of each of them.
Composites are gaining a wide range of applications in engineering because of the
following advantages: weight savings, corrosion resistance, easy manufacturing,
low temperature processing, possibility of producing novel shapes, reduced parts
and long fatigue life (Nowosielki et al, 2006;Ranganathatiah,2010).
Composites can be made of two or more components, the matrix and the
dispersed phase. The properties of a composite material depend on the following :
properties of the matrix; properties and distribution of reinforcement, nature of
bonding at the interface and volume fractions occupied by the constituents (Lake,
2002).
A matrix is a material in which the reinforcements or other components of a
composite system are embedded. It can be made of metal, ceramic or polymer
(Askeland, 1994). The purpose of the matrix is to bind the reinforcements together
by virtue of its cohesive and adhesive characteristics, to transfer load to and
between the reinforcements and to protect the reinforcements from environment
and handling. The matrix is often the weak link in a composite when viewed from
a structural perspective. Chemical treatment of reinforcement materials or filler
increase interfacial adhesion between the matrix and fillers leading to better
mechanical properties of the composites (Gauthier et al, 1998). It is in view of
these expected roles of matrix materials that epoxy resin was used in this study.
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A polymer matrix composite is a composite formed by the combination of a
polymer (resin) matrix and a fibrous reinforcing phase (Ezuanmustapha et al,
2005). Polymer composites are gaining importance as substitute for metals in
applications in the aerospace, automotive, marine, sporting goods and electronics
industries due to their light weight and corrosion resistance. Polymer matrix can
be classified as thermoplastics and thermo set. Thermoplastics include low density
polyethylene, high density polyethylene, nylon, polypropylene and polyester while
epoxy resin is an example of a thermo set.
Epoxy resin is currently of much research interest due to its superior properties
over polyester resin. Some of the properties of the epoxy resin identified by
researchers are low cure shrinkage, better resistance to moisture, better
mechanical properties, processing flexibility and better handling.
Epoxy resins are presently used more than all other matrices in advanced
composite materials for structural applications in the United States of
America(USA) Air Force and Navy. The dispersed phase of a composite refers to
the reinforcement or fillers added in the matrix and the role of reinforcement in
a composite material is to increase the mechanical properties of the neat resin
system (Askeland, 1994).
Filler materials are generally the inert materials which are used in composite
materials to reduce cost, absorb thermal stresses, improve mechanical properties
to some extent and in some cases to improve processing (Singla and Chawla,
2010). Fillers which increase bulk volume and hence reduce cost are known as
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extender fillers while those that improve mechanical properties particularly tensile
strength are termed reinforcing fillers (Igwe and Onuegbu, 2010).
Many researchers like Suwanprateeb and Hathapamit(2002), Zemke and
Woods(2009) are optimistic to find out whether rice husk ash is a reinforcing
filler or an extender filler. The current challenge is to make composite production
cost effective and this has resulted to high filler loadings. An interface is the
boundary between the individual, physically distinguishable constituents of a
composite. It is the bonding surface or zone where discontinuity occurs. Interface
must be large and exhibit strong adhesion between the fibers and the matrix.
Wetting occurs at the interface and its failure at the interface is called debonding
which may or may not be desirable. Interfacial bonding is a bonding type in
which the surfaces of two bodies in contact with one another are held together by
intermolecular forces like covalent, ionic, vanderwaals and hydrogen bonds.
Interfaces have been identified as zones where compositional, structural and
mechanical properties are altered in composites. Mechanical properties are
properties of a material that are associated with elastic and inelastic reaction when
force is applied or the properties involving relationship between stress and
strain(Royalance, 2008).
Microstructure is the microscopic description of individual constituents of
a material. Microstructure studies of composites show what happens at the atomic
and microscopic levels of the interface.
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Electron microscopy analysis is used to characterize the microstructure of
composites. Scanning electron microscopy shows the morphology and topography
of the composites while compositional analysis is conducted using energy
dispersive x-ray spectroscopy. Energy dispersive x-ray spectroscopy is a chemical
microanalytical technique used in conjunction with scanning electron microscopy
to determine the elements in the microstructure of a material.
1.2 Statement of the Problem
Most developing countries like Nigeria are not yet properly utilizing
agricultural wastes such as rice husk ash for gainful engineering production. Rice
husk ash constitutes environmental pollution and causes health hazards like
silicosis, cancer, tuberculosis, chronic cough and sight disorder in areas where it is
dumped. Therefore there is need to develop more ways of reducing the amount of
the waste in the environment. One of the easiest ways of solving the problem is to
rice husk ash as filler in epoxy matrix to form epoxy-rice husk ash composite.
Epoxy based composites can be used in producing sole of shoes, side stools ,slabs,
industrial flooring and other components for electrical and industrial engineering.
Material engineers are facing the problem of developing materials that have
low cost, light weight and enhanced mechanical properties for executing
construction works. Metals which have good strength are insidiously affected by
corrosion and heavy weight making the search for alternative materials like epoxy
based composites that can be substituted for metals in some engineering
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applications inevitable. Particle filled composites are gaining wide research
interest due to the problem of delamination and fiber pullout associated with
fibrous composites. The behavior of epoxy resins have not been fully understood
by researchers especially its slow curing character. Microstructural study of the
effect of interfacial adhesions between particle and matrix is fundamental in
understanding mechanical behavior of polymer composites.
1.3 Objectives of the Study
The general objective of this project is to characterize composite materials
produced from different compositions of epoxy and rice husk ash. The specific
objectives of the study are:
1. To produce epoxy-rice husk ash composite using rice husk ash considered as
an agricultural waste as a filler.
2. To conduct scanning electron microscopy and energy dispersive x-ray
spectroscopy analysis on epoxy –rice husk ash composite and study the
effect of variation of rice husk ash volume fractions on the microstructure.
3. To carry out scanning electron microscopy on Adani Rice husk ash.
4. To examine the effect of rice husk ash volume fraction on some mechanical
properties of epoxy- rice husk ash composite and ascertain the suitability of
the composite for engineering applications.
1.4 Justification of the Study
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This study is valuable in understanding the potentials of rice husk ash as
filler in composite production and the behavior of Epoxy resins. The study is
useful to engineers and researchers in the composite industry because it will help
to suggest ways of improving the mechanical properties of the epoxy-rice husk ash
composite. Composite production can offer employment opportunity to
unemployed youths due to low energy and machinery requirements for
production. The knowledge of microstructure and mechanical properties of
particle filled composites is vital in describing the behaviours at the interface and
the effect of forces on the composites. Proper understanding of the microstructure
and mechanical properties of composites will help to ascertain the engineering
application of composite in structures, industries, electronics, oil and gas, and
other industrial production.
1.5 Scope and Limitations of the Study
Experimental approach was used in this study involving composite
production, microstructural analysis using scanning electron microscopy and
energy dispersive x-ray spectroscopy as well as the determination of the
mechanical properties of the composite material. The composites were produced at
0%, 10%, 20%, 30% 40% and 50% volume fraction of rice husk ash fillers. The
rice husk used in the study was sourced from Adani rice mill, Enugu State,
Nigeria. Apart from production of the amorphous rice husk ash at 550oC all other
experiments were done at room temperature. In order to adequately view the
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particle and matrix interfacial interactions two magnifications of 200x and 2000x
were used for the scanning electron microscopy analysis. Lack of accessibility to
transmission electron microscope hindered possibility of investigating other
microstructural features. Other limitations faced in the research were sourcing the
epoxy resin and getting the characterization equipment
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