MECHANICAL AND SOLID PARTICLE EROSION BEHAVIOR OF MODIFIED RICE-HUSK FILLED EPOXY COMPOSITE

MECHANICAL AND SOLID PARTICLE EROSION BEHAVIOR OF MODIFIED RICE-HUSK FILLED EPOXY COMPOSITE
MECHANICAL AND SOLID PARTICLE EROSION
BEHAVIOR OF MODIFIED RICE-HUSK FILLED
EPOXY COMPOSITE
A THESIS SUBMITTED IN PARTIAL FULFILMENT OF
THE REQUIREMENT FOR THE DEGREE OF
Master of Technology
In
Mechanical Engineering
(Specialization- Machine Design & Analysis)
By
Ajeet Bahadur Singh
Department of Mechanical Engineering
National Institute of Technology, Rourkela
769008, India
2011-2013
MECHANICAL AND SOLID PARTICLE EROSION
BEHAVIOR OF MODIFIED RICE-HUSK FILLED
EPOXY COMPOSITE
A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE
REQUIREMENT FOR THE DEGREE OF
Master of Technology
In
Mechanical Engineering
(Specialization- Machine Design & Analysis)
Submitted to
National Institute of Technology, Rourkela
(Deemed University)
By
Ajeet Bahadur Singh
Under the supervision of
Dr. Sameer Kumar Acharya
Department of Mechanical Engineering
National Institute of Technology, Rourkela
769008, India
2011-2013
Dedicated to
My Parents
Mr. Baratu Bahadur Singh
&
Mrs. Uttara Devi
National Institute of Technology, Rourkela
769008, Orissa, INDIA
CERTIFICATE
This is to certify that the thesis entitled “Mechanical and Solid Particle Erosion
Behavior of Modified Rice-Husk Filled Epoxy Composite” submitted to the National
Institute of Technology, Rourkela (Deemed University) by Ajeet Bahadur Singh, Roll
No. 211ME1163 for the award of the Degree of Master of Technology in Mechanical
Engineering (Specialization– Machine Design & Analysis) is a record of bonafide
research work carried out by him under my supervision and guidance. The results
presented in this thesis has not been, to the best of my knowledge, submitted to any other
University or Institute for the award of any degree or diploma.
The thesis, in my opinion, has reached the standards fulfilling the requirement for the
award of the degree of Master of Technology in accordance with regulations of the
Institute.
Date:
/June/2013
(Dr. S. K. Acharya)
Associate Professor
Mechanical Engineering Department
i
Acknowledgement
With deep regards and profound respect, I avail this opportunity to express my deep
sense of gratitude and indebtedness to Dr. S. K. Acharya, Department of Mechanical
Engineering, National Institute of Technology Rourkela, for suggesting the topic of my
thesis report and for his inspiring guidance, constructive criticism and valuable
suggestion throughout the project work. I most gratefully acknowledge his constant
encouragement and help in different ways to complete this project successfully.
I would like to acknowledge my deep sense of gratitude to Prof. K. P. Maity, Head,
Department of Mechanical Engineering, National Institute of Technology Rourkela, for
his valuable advices and constant encouragement for allowing me to use the facilities in
the laboratory.
I also express my thanks to Dr. S. K. Pratihar of Ceramic Engineering Department for
helping in the different tests & studies in his department.
I wish to thank all the faculty members & staffs of Department of Mechanical
Engineering for their support and help during the project.
I am thankful to Mr. G. Raghavendra and all my lab mates and PhD students of
mechanical department for their valuable support and maintaining a nice research
environment in the laboratory. I am also thankful to Mr. D. Mahto for his co-operation in
my experimental work.
Last but not the least; I would like to express my gratefulness to my parents & family
members for their endless support, without which I could not have completed my project
work.
Date: 03/06/2013
Ajeet Bahadur Singh
Roll No. 211ME1163
ii
ABSTRACT
In today’s modern age growing population and product requirement has triggered
the issue of low cost manufacturing material which should also be renewable resource to
meet the requirement easily anywhere in the world. Composites are combination of two
or more materials that provide characteristics which cannot be achieved by single
material system. This is achieved by cohesion of the materials made by physically
combining two or more compatible materials, different in characteristics, composition
and sometimes in form. Efforts have been made in many researches in the field of
composite to make it low cost, easy availability, ecofriendly and also that it can fulfill all
the criteria of its ease of manufacturing and usage. Natural fibers have attracted attention
of many researchers as filler for the composite materials because of their low cost,
ecofriendly and ease of availability; hence natural fibers are suitable alternative of
traditional synthetic and inorganic fibers. Accordingly extensive studies on preparation of
polymer matrix composite (PMC) replacing the synthetic fibers with natural fibers like
Jute, Sisal, Pineapple, Bamboo, Kenaf and Bagasse were carried out. These plant fibers
have many advantages over glass fiber or carbon fiber like renewability, environmental
friendly, low cost, lightweight and high specific mechanical performance.
Among the various biomasses, with abundant and renewable energy sources, rice
husk (RH) is a potential source of energy which can easily be available anywhere since it
is a byproduct of rice mill. It has already been utilized in many useful applications such
as light weight concrete, an insulating material, fillers in plastics, building materials
(bricks), panel boards and activated carbon, electricity generation and husk-fueled steam
engines etc. Rice husk has a characterization of hard surface, high silicon content, small
bulk density. Against this back ground the present research work has been undertaken
with an objective to explore the use of natural fiber Rice-Husk, as a reinforcement
material in epoxy base. Mechanical and solid particle erosion wear behaviors of RiceHusk reinforced epoxy polymer composite have been studied. All these tests have been
carried out as per ASTM standard. To study the mechanical and erosion properties of the
composite, different volume fraction of fiber have been taken (5%, 10%, 15% & 20%).
These fibers were randomly distributed in the matrix. Usual hand lay -up technique has
iii
been adopted for manufacturing the composite. To have a good compatibility between the
fiber and matrix, fibers were chemically treated with acetone and alkali. It was observed
that tensile and flexural strength increases with increase in fiber content and best result
was found for 15% wt. fraction of RH fiber reinforced epoxy composite. Solid particle
erosion test was also carried out and significant reduction in erosion strength was found
in the RH fiber filled epoxy composite compared to neat epoxy. It was observed that
modified fiber increases the strength as well as erosion behavior appreciably. Erosion test
of the samples characterized the RH-epoxy composite as a semi-brittle material. Finally
scanning electron microscopy (SEM) and x-ray diffraction (XRD) tests has been carried
out which further explains the characteristics of the composite samples.
iv
TABLE OF CONTENTS
Certificate
i
Acknowledgements
ii
Abstract
iii
Contents
vi
List of Tables
ix
List of Figures
x
List of Symbols
xii
v
CHAPTER-1 ............................................................................ 1
1.1 BACKGROUND ...................................................................................................... 1
1.2 COMPOSITES......................................................................................................... 2
1.2.1 Why a Composite? ......................................................................................... 2
1.2.2 What is a composite? .................................................................................... 3
1.2.3 Characteristics of the Composites ................................................................. 4
1.2.4 Classification of Composites .......................................................................... 5
1.2.4.1 Particulate Composites ...................................................................................... 5
1.2.4.2 Fibrous composites ............................................................................................ 5
1.3 COMPONENTS OF A COMPOSITE MATERIAL ........................................................ 7
1.3.1 Role of matrix in a composite ........................................................................ 7
1.3.2 Materials used as matrices in composites ..................................................... 7
1.3.2.1 Bulk-Phases ........................................................................................................ 8
a)
Metal Matrices ................................................................................................... 8
b)
Polymer Matrices ............................................................................................... 9
c)
Ceramic Matrices ............................................................................................. 10
1.3.2.2 Reinforcement ................................................................................................. 12
1.3.2.3 Interface ........................................................................................................... 12
1.4 TYPES OF COMPOSITE MATERIALS ..................................................................... 12
1.4.1 Fiber-reinforced composites ........................................................................ 12
1.4.1.1 Continuous or long fiber composite ................................................................ 13
1.4.1.2 Discontinuous or short fiber composite .......................................................... 13
1.4.2 Laminate Composites .................................................................................. 14
1.5 THESIS OUTLINE .................................................................................................. 15
CHAPTER-2 .......................................................................... 16
2.1 LITERATURE SURVEY ........................................................................................... 16
2.2 NATURAL FIBERS: INITIATIVE IN PRODUCT DEVELOPMENT. .......................................... 16
2.3 OBJECTIVE OF THE RESEARCH WORK ................................................................. 20
vi
CHAPTER-3 .......................................................................... 21
3.1 INTRODUCTION .................................................................................................. 21
3.2 THEORY OF WEAR ............................................................................................... 21
3.3 TYPES OF WEAR .................................................................................................. 22
3.3.1 Abrasive wear .............................................................................................. 22
3.3.2 Adhesive wear.............................................................................................. 23
3.3.3 Erosive wear................................................................................................. 23
3.3.4 Surface fatigue wear.................................................................................... 24
3.3.5 Corrosive wear ............................................................................................. 24
3.4 SYMPTOMS OF WEAR ......................................................................................... 25
3.5 FABRICATION OF COMPOSITES .......................................................................... 26
3.5.1 Rice husk ...................................................................................................... 26
3.5.2 Epoxy Resin & Hardner ................................................................................ 27
3.6 FABRICATION & PREPARATION OF COMPOSITE SLABS ...................................... 27
3.7 TENSILE TEST ....................................................................................................... 28
3.8 BEND TEST .......................................................................................................... 29
3.9 RESULTS OF TENSILE TEST AND BEND TEST ........................................................ 30
3.10 SOLID PARTICLE EROSION TEST ........................................................................ 32
3.11 EXPERIMENT ..................................................................................................... 33
3.11.1 Preparation for the test specimens ........................................................... 33
3.11.2 Test apparatus & Experiment .................................................................... 34
3.12 RESULTS & DISCUSSION .................................................................................... 35
3.13 CONCLUSIONS .................................................................................................. 37
CHAPTER-4 .......................................................................... 55
4.1 INTRUDUCTION .................................................................................................. 55
4.2 CHEMICAL MODIFICATIONS OF FIBERS .............................................................. 55
4.3 METHODS OF CHEMICAL MODIFICATIONS ......................................................... 56
4.3.1 Acetone Treatment ...................................................................................... 56
vii
4.3.2 Alkali Treatment .......................................................................................... 56
4.3.3 Benzoyl Chloride Treatment ........................................................................ 57
4.3.4 Silane Treatment.......................................................................................... 57
4.3.5 Permanganate Treatment ........................................................................... 58
4.3.6 Peroxide Treatment ..................................................................................... 58
4.3.7 Isocyanate Treatment .................................................................................. 59
4.3.8 Acrylic Acid Treatment ................................................................................. 59
4.3.9Maleic anhydride Treatment ........................................................................ 59
4.3.10 Sodium chlorite (NaClO2) Treatment ......................................................... 59
4.4 FABRICATION OF COMPOSITES WITH MODIFIED RH AS REINFORCEMENT ........ 60
4.4.1 Fiber preparation with acetone treatment:................................................. 60
4.4.2 Fiber preparation with alkali treatment: ..................................................... 60
4.5 PREPARATION OF COMPOSITE SLABS FOR TENSILE TEST AND BEND TEST ......... 61
4.6 TENSILE TEST AND BEND TEST ............................................................................ 61
4.7 RESULTS AND DISCUSSION: ................................................................................ 61
4.8 PREPARATION OF SPECIMENS FOR SOLID PARTICLE EROSION TEST .................. 63
4.9 CALCULATION ..................................................................................................... 63
4.10 X-RAY DIFFRACTION.......................................................................................... 63
4.11 SCANNING ELECTRON MICROSCOPY STUDY .................................................... 63
4.12 RESULTS AND DISCUSSION ............................................................................... 64
4.13 CONCLUSION .................................................................................................... 64
CHAPTER-5 .......................................................................... 93
5.1 CONCLUSION ...................................................................................................... 93
5.2 RECOMMENDATIONS AND FUTURE SCOPE FOR RESEARCH WORK ................... 94
viii
List of Tables
Table No.
Title
Page No.
1.1
Classification of composite ......................................................................... 6
1.2
Types of marices ......................................................................................... 8
1.3
Advantages and limitations of polymer matrix materials .......................... 9
1.4
Types of Thermoplastics & Thermosets ................................................... 10
1.5
Application temperatures of some matrix material ................................. 11
1.6
Trends for temperature application of heat resistant composites .......... 11
2.1
Properties of natural fibers ....................................................................... 17
3.1
Symptoms and appearance of different types of wear ............................ 25
3.2
Mechanical properties of PRH reinforced ................................................ 31
epoxy & Neat Epoxy composites
3.3
Particle velocity under different pressure ................................................ 39
3.4
Experimental parameters for the erosion test ......................................... 39
3.5 – 3.9
Cumulative weight loss & erosion rate of PRH & Epoxy .......................... 40
3.10
Parameters characterizing the velocity dependence of. .......................... 45
erosion rate of Neat Epoxy & PRH reinforced composite
3.11
Erosion efficiency (η) of neat epoxy samples ........................................... 46
3.12
Erosion efficiency (η) of PRH composite samples .................................... 47
4.1
Tensile and flexural strength for acetone treated .................................... 61
rice husk reinforced epoxy composites
4.2
Tensile and flexural strength for alkali treated ........................................ 62
rice husk reinforced epoxy composites
ix
4.3 – 4.10
Weight loss & erosion rate of treated RH epoxy composite .................... 66
different velocities and angles
4.11
Parameters characterizing the velocity dependence of erosion .............. 74
rate of treated RH reinforced epoxy composite.
4.12
Erosion efficiency (η) of acetone treated RH............................................ 76
reinforced epoxy composite.
4.13
Erosion efficiency (η) of alkali treated RH reinforced epoxy composite .. 77
List of Figures
Figure No.
Title
Page No.
1.1
Schematic diagram of different types of Composite ............................... 14
2.1
Overview of natural fiber .......................................................................... 18
2.2
Photograph of Rice Husk .......................................................................... 20
3.1
Schematic representations of the abrasion wear mechanism ................ 23
3.2
Schematic representations of the adhesive wear mechanism ................ 23
3.3
Schematic representations of the erosive wear mechanism .................. 24
3.4
Schematic representations of the surface fatigue wear mechanism ....... 24
3.5
(a) Mold used for composite preparation ............................................... 28
(b) Specimen cut for bend test
(c) Specimen cut for erosion test.
3.6
INSTRON H10KS TESTING MACHINE ......................................................... 29
3.7
Loading position of specimen for bend test ............................................. 30
3.8
Variation of tensile strength with increasing weight ............................... 31
x
% of rice husk reinforcement in the composite
3.9
Variation of flexural strength with increasing weight .............................. 32
of rice husk reinforcement in the composite
3.10
Details of erosion test rig .......................................................................... 48
3.11 – 3.14
Variation of erosion rate with impingement ............................................ 49
angle of various PRH-epoxy composite
3.15 – 3.18
Histogram showing the steady state erosive wear .................................. 51
rates of all the composites of PRH & epoxy
3.19 – 3.22
Variation of steady-state erosion rate of neat epoxy and ........................ 53
PRH-epoxy composites as a function of impact velocity
4.1
Effect of fiber modification by acetone and alkali .................................... 62
treatment on tensile strength
4.2
Effect of fiber modification by acetone and alkali .................................... 62
treatment on flexural strength
4.3
Soxhlet Extractor ....................................................................................... 78
4.4 – 4.19
Comparison of erosion rate versus impingement ................................... 79
angle of treated and untreated RH
4.20 – 4.27
Variation of steady-state erosion rate of treated..................................... 87
RH-epoxy composites as a function of impact velocity
4.28
XRD Pattern of untreated and treated Rice-Husk fiber ........................... 91
4.29
SEM micrographs of eroded surface of untreated ................................... 92
and treated Rice-Husk fiber
xi
List of Symbols
FRP
Fiber Reinforced Plastic
PMC
Polymer Matrix Composite
RH
Rice Husk
σ
Tensile Strength
δ
Deflection of the speciment
P
Load
A
Cross sectional Area
L
Span length
E
Young’s modulus
UTM
Ultimate testing machine
FS
Flexural Strength
b
Breadth of specimen
t
Thickness of specimen
G
Flexural Modulus
y
Extension of the specimen
PRH
Plain Rice-Husk
Er
Erosion Rate
v
Velocity of impingement
n
Velocity exponent
Δw
Weight loss
we
Weight of eroding particle
η
Erosion efficiency
H
Hardness of the composite
ρ
Density of the composite
xii
Chapter-1
1.1 BACKGROUND
Composite materials have been used by men since ancient age and yarn is
probably one of the greatest developments of mankind which enabled him to survive
any climate area and to explore the surface of the earth hence flexible fabrics made of
cotton, flax and jute were excellent compared to animal skins. Age after age use of the
composite materials with natural resources increased continuously in the form of
straw reinforced walls, composite bows and cross bows, chariots made of the
combination of layers of wood, bones and horns. In today’s modern age growing
population and product requirement has triggered the issue of low cost manufacturing
material which should possess mechanical properties good enough to meet the
standards and which can also be renewable resource to meet the requirement easily
anywhere in the world. Composite materials with natural fiber have attracted
attentions of many researchers worldwide because of their low cost and ease of
manufacturing.
In these days polymer composite materials are extensively used in engineering
applications due to their excellent specific physical and chemical properties. They
also find applications in fields where high resistance to wear, abrasion and erosion is
required (mining, automobile, domestic equipment, aerospace, marine, sports etc.).
Automobile industries are showing the highest interest towards natural fiber
composites and also in many European countries they have already decided to use
mostly bio-degradable and ecofriendly materials for the manufacturing of the
automobile components especially in cars.
Composite materials have been seen in nature from small plants to huge trees they
are all made of natural fiber composite with combination of cellulose-lignin
compound with the hydrogen bonding, on the other hand we also see composite
materials used by nature as teeth, bones & muscle tissues. The market research firm
Frost & Sullivan says that, as early as 2015, lignin will be used commercially as
replacement for phenol for manufacturing of resins, adhesives, surfactants or
polyester. The advantage of natural fibers is their high stiffness, better strength to
weight ratio and low cost whereas their disadvantage is they are highly sensitive to
1
moisture absorption. The moisture absorption sensitivity of natural fibers can be
reduced by chemical processing of fibers but that induces extra cost but still we can
afford a cost effective product compared to synthetic fiber composite and other
materials.
1.2 COMPOSITES
1.2.1 Why a Composite?
A composite is a structural material that consists of two or more combined
constituents that are combined at a macroscopic level and are not soluble in each
other. For many decades composite materials are replacing the other manufacturing
materials because of their low cost, easy availability and good mechanical properties.
Composites have already proven their worth as weight-saving materials; now the
current challenge is to make them cost effective. There have been derived many
manufacturing techniques to economically fabricate composite material by the
composite industries. Improvement in composite manufacturing technique alone is not
sufficient to reduce the cost of the composite significantly hence it is important to pay
attention in other phases also like design, material to be used, process of fabrication,
tools and machines used, quality control, time of fabrication and also the program
management to reduce the overall cost of the composite effectively.
Composite materials have been used widely by the aerospace industries during
past several years and now it is shifting rapidly towards commercial use as a
manufacturing material for various applications.
Unlike the conventional materials like steel, copper, aluminium etc. the properties
of the composite materials can be designed considering structural aspects.
The design of a structural component using composites involves both material and
structural design. The variations of composite properties such as stiffness, thermal
expansion etc. can be controlled of the designer in a broad range of values. Careful
selection of reinforcement type enables finished product characteristics to be tailored
to almost any specific engineering requirement.
By the introduction of newer polymer resin matrix materials and high
performance reinforcement fibers such as glass, aramid and carbon the use of
composite materials as a replacement in complex and advanced materials has gain
greater scope. High performance FRP can now be found in such diverse applications
2
as composite armoring designed resist explosion impacts, windmill blades, fuel
cylinders for natural gas vehicles, industrial drive shafts, making rollers and also in
bridges For certain applications, the use of composites rather than metals has in fact
resulted in savings of both cost and weight. Some examples are curved fairing and
fillets, cascades for engines, replacements for welded metallic parts, tubes, cylinders,
blade containment bands, ducts etc.
Externally bonded fibre reinforced polymers (FRPs) in the form of continuous
glass, carbon, or aramid fibres bonded together in a matrix made of epoxy, polyester
or vinylester, are being employed extensively throughout the world as a reinforced
concrete structures for retrofitting. They possess properties like high strength-toweight ratio, highly capable to absorb shocks and vibration, ease of handling and
installation, immunity to corrosion etc. and hence FRP jackets are being used
increasingly as material of choice for seismic retrofitting projects, even after their
relatively high material costs.
Whilst the use of composites will be a clear choice in many cases, material
selection in others will depend on factors such as working lifetime requirements,
number of items to be produced (run length), complexity of product shape, possible
savings in assembly costs and on the experience & skills the designer in tapping the
optimum potential of composites. In instances, best results may be achieved through
the use of composites in conjunction with traditional materials.
1.2.2 What is a composite?
A typical composite material is a system of materials composing of two or more
materials (mixed and bonded) on a macroscopic scale.
Generally, a composite material is composed of reinforcement (fibers, particles,
flakes, and/or fillers) embedded in a matrix (polymers, metals, or ceramics). The
matrix holds the reinforcement to form the desired shape while the reinforcement
improves the overall mechanical properties of the matrix. When designed properly,
the new combined material exhibits better strength than would each individual
material.
As defined by Jartiz, [1] Composites are multifunctional material systems that
provide characteristics not obtainable from any discrete material. They are cohesive
structures made by physically combining two or more compatible materials, different
incomposition and characteristics and sometimes in form.
3
Kelly [2] very clearly stresses that the composites should not be regarded simple
as a combination of two materials. In the broader significance; the combination has its
own distinctive properties. In terms of strength or resistance to heat or some other
desirable quality, it is better than either of the components alone or radically different
from either of them.
Berghezan [3] defines as “The composites are compound materials which differ
from alloys by the fact that the individual components retain their characteristics but
are so incorporated into the composite as to take advantage only of their attributes and
not of their shortcomings”, in order to obtain an improved material.
Van Suchetclan [4] explains composite materials as heterogeneous materials
consisting of two or more solid phases, which are in intimate contact with each other
on a microscopic scale. They can be also considered as homogeneous materials on a
microscopic scale in the sense that any portion of it will have the same physical
property.
1.2.3 Characteristics of the Composites
Composites consist of one or more discontinuous phases embedded in a
continuous phase. The discontinuous phase is usually harder and stronger than the
continuous phase and is called the ‘reinforcement‘ or ‘reinforcing material’, whereas
the continuous phase is termed as the ‘ matrix’.
Properties of composites are strongly dependent on the properties of their
constituent materials, their distribution and the interaction among them. The
composite properties may be the volume fraction sum of the properties of the
constituents or the constituents may interact in a synergistic way resulting in
improved or better properties. Apart from the nature of the constituent materials, the
geometry of the reinforcement (shape, size and size distribution) influences the
properties of the composite to a great extent. The concentration distribution and
orientation of the reinforcement also affect the properties.
The shape of the discontinuous phase (which may by spherical, cylindrical, or
rectangular cross-sanctioned prisms or platelets), the size and size distribution (which
controls the texture of the material) and volume fraction determine the interfacial
area, which plays an important role in determining the extent of the interaction
between the reinforcement and the matrix.
4
Concentration, usually measured as volume or weight fraction, determines the
contribution of a single constituent to the overall properties of the composites. It is not
only the single most important parameter influencing the properties of the composites,
but also an easily controllable manufacturing variable used to alter its properties
1.2.4 Classification of Composites
Composite materials can be classified in different ways [5]. Classification based
on the geometry of a representative unit of reinforcement is convenient since it is the
geometry of the reinforcement which is responsible for the mechanical properties and
high performance of the composites. A typical classification is presented in Table-1.1.
The two broad classes of composites are:
1. Fibrous composites
2. Particulate composites
1.2.4.1 Particulate Composites
As the name itself indicates, the reinforcement is of particle nature (platelets are
also included in this class). It may be spherical, cubic, tetragonal, a platelet, or of
other regular or irregular shape, but it is approximately equiaxed. In general, particles
are not very effective in improving fracture resistance but they enhance the stiffness
of the composite to a limited extent. Particle fillers are widely used to improve the
properties of matrix materials such as to modify the thermal and electrical
conductivities, improve performance at elevated temperatures, reduce friction,
increase wear and abrasion resistance, improve machinability, increase surface
hardness and reduce shrinkage.
1.2.4.2 Fibrous composites
A fiber is characterized by its length being much greater compared to its crosssectional dimensions. The dimensions of the reinforcement determine its capability of
contributing its properties to the composite. Fibers are very effective in improving the
fracture resistance of the matrix since a reinforcement having a long dimension
discourages the growth of incipient cracks normal to the reinforcement that might
otherwise lead to failure, particularly with brittle matrices.
Man-made filaments or fibers of non-polymeric materials exhibit much higher
strength along their length since large flaws, which may be present in the bulk
5
material, are minimized because of the small cross-sectional dimensions of the fiber.
In the case of polymeric materials, orientation of the molecular structure is
responsible for high strength and stiffness.
Table- 1.1: Classification of composite
6
Fibers, because of their small cross- sectional dimensions, are not directly usable
in engineering applications. They are, therefore, embedded in matrix materials to form
fibrous composites. The matrix serves to bind the fibers together, transfer loads to the
fibers, and protect them against environmental attack and damage due to handling. In
discontinuous fiber reinforced composites, the load transfer function of the matrix is
more critical than in continuous fiber composites.
1.3 COMPONENTS OF A COMPOSITE MATERIAL
In its most basic form a composite material is one, which is composed of at least
two elements working together to produce material properties that are different to the
properties of those elements on their own. In practice, most composites consist of a
bulk material (the ‘matrix’), and a reinforcement of some kind, added primarily to
increase the strength and stiffness of the matrix.
1.3.1 Role of matrix in a composite
Many materials when they are in a fibrous form exhibit very good strength but to
achieve these properties the fibers should be bonded by a suitable matrix. The matrix
isolates the fibers from one another in order to prevent abrasion and formation of new
surface flaws and acts as a bridge to hold the fibers in place. A good matrix should
possess ability to deform easily under applied load, transfer the load onto the fibers
and evenly distributive stress concentration.
A study of the nature of bonding forces in laminates [6] indicates that upon initial
loading there is a tendency for the adhesive bond between the reinforcement and the
matrix to be broken. The frictional forces between them account for the high strength
properties of the laminates.
1.3.2 Materials used as matrices in composites
In its most basic form a composite material is one, which is composed of at least
two elements working together to produce material properties that are different to the
properties of those elements on their own. In practice, most composites consist of a
bulk material (the matrix) and a reinforcement of some kind, added primarily to
increase the strength and stiffness of the matrix.
7
1.3.2.1 Bulk-Phases
a) Metal Matrices
Metal matrix composites possess some attractive properties, when compared with
organic matrices. These include (i) strength retention at higher temperatures, (ii)
higher transverse strength, (iii) better electrical conductivity, (iv) superior thermal
conductivity, (v) higher erosion resistance etc. However, the major disadvantage of
metal matrix composites is their higher densities and consequently lower specific
mechanical properties compared to polymer matrix composites. Another notable
difficulty is the high-energy requirement for fabrication of such composites.
Metal Matrix
Composites
(MMC)
Thermosets
Polymer Matrix
Composites (PMC
Matrice
Ceramic Matrix
Composites (CMC)
Thermoplastics
Carbon and Graphic
Matrix Composites
(CGMC)
Table- 1.2: Types of marices.
In the aerospace industry interest has been concentrated primarily on fiber
reinforced aluminium and titanium. Boron and to a lesser extent silicon carbide (SiC),
have been investigated as the reinforcing fibers. Aluminium alloys reinforced with
boron have been extensively produced by a variety of methods. Titanium reinforced
with SiC, boron (coated with SiC) and beryllium, used for compressor blades.
Good elastic modulus properties can be achieved by the unidirectional
incorporation of fibers or whiskers in the metal matrix even though the bonding
between them may be poor. But, strong metallic matrices rather than weak metal or
polymer matrices are essential for good transverse modulus and shear strength.
Carbon/graphite fibers have been used with metal matrices on a laboratory /
experimental scale only, because most basic fabrication techniques involve high
8
temperatures which have detrimental effects on the fiber. However, research on these
lines is continuing in view of the potential of the composites.
b) Polymer Matrices
A very large number of polymeric materials, both thermosetting and
thermoplastic, are used as matrix materials for the composites. Some of the major
advantages and limitations of resin matrices are shown in Table-1.3
Table- 1.3: Advantages and limitations of polymer matrix materials
Advantages
Limitations
Low densities
Low transverse strength
Good corrosion resistance
Low operational temperature limits
Low thermal conductivities
Low electrical conductivities
Translucence
Aesthetic Colour effects
Usually the resinous binders (polymer matrices) are selected on the basis of
adhesive strength, fatigue resistance, heat resistance, chemical and moisture resistance
etc. The resin must have mechanical strength commensurate with that of the
reinforcement. It must be easy to use in the fabrication process selected and also stand
up to the service conditions. Apart from these properties, the resin matrix must be
capable of wetting and penetrating into the bundles of fibers which provide the
reinforcement, replacing the dead air spaces therein and offering those physical
characteristics capable of enhancing the performance of fibers.
Shear, chemical and electrical properties of a composite depend primarily on the
resin. Again, it is the nature of the resin that will determine the usefulness of the
laminates in the presence of a corroding environment.
Thermoplastics
Polyethylene
Polysyrene
Polyamides
(a)
9
Nylons
Polypropylene
Thermosets
Epoxy
Phenolic
Polyamide
Resins
Polyester
(b)
Table- 1.4: Types of Thermoplastics & Thermosets
Generally speaking, it can be assumed that in composites, even if the volume
fraction of the fiber is high (of the order of 0.7), the reinforcement is completely
covered by the matrix material; and when the composite is exposed to higher
temperatures it is the matrix, which should withstand the hostile environment. Of
course, the strength properties of the composite also show deterioration, which may
be due to the influence of the temperature on the interfacial bond. Thus, the high
temperature resistant properties of the composites are directly related more to the
matrix, rather than to the reinforcement. The search for polymers which can withstand
high temperatures has pushed the upper limit of the service temperatures to about
300-350°C. This range of operational temperatures can be withstood by polyimides,
which are the state-of-the-art high temperature polymers for the present.
Table-1.3 and 1.4 indicate the approximate service temperature ranges for the
resins and composites [7, 8]. It should be remembered that there is no place for
compromise as to the nature of the matrix material, particularly when it comes to the
application temperature of the composite. If the application temperature exceeds 300350°C metal matrix appears to be the only alternative, at least for the present.
c) Ceramic Matrices
Ceramic fibres, such as alumina and SiC (Silicon Carbide) are advantageous in
very high temperature applications, and also where environment attack is an issue.
Since ceramics have poor properties in tension and shear, most applications as
reinforcement are in the particulate form (e.g. zinc and calcium phosphate). Ceramic
Matrix Composites (CMCs) used in very high temperature environments, these
materials use a ceramic as the matrix and reinforce it with short fibres, or whiskers
such as those made from silicon carbide and boron nitride.
10
Table- 1.5 Application temperatures of some matrix material
Limit of
Matrix material
Long term exposure,
°C
Short term exposure,
°C
Unsaturated polyesters
70
100
Epoxies
125
200
Phenolics
250
1600
Polyimides
315
400
Aluminium
300
350
Table- 1.6 Trends for temperature application of heat resistant composites
Fiber reinforced
Composite
Maximum service
temperature, °C
Specific weight
gm/cm3
Carbon / Epoxy
180
1.4
Boron/Epoxy
180
2.1
Borsic / Aluminium
310
2.8
Carbon/Polyimide
310
1.4
Boron/Polyimide
310
2.1
Carbon/Polyaminoxaline
350
1.4
Carbon/Polybenzthiazole
400
1.4
Borsic/Titanium
540
3.6
Carbon/Nickel
930
5.3
Whisker/Metals
1800
2.8-5.6
11
1.3.2.2 Reinforcement
The role of the reinforcement in a composite material is fundamentally one of
increasing the mechanical properties of the neat resin system. All of the different
fibres used in composites have different properties and so affect the properties of the
composite in different ways. For most of the applications, the fibres need to be
arranged into some form of sheet, known as a fabric, to make handling possible.
There are different ways for assembling fibers into sheets and the variety of fiber
orientations possible to achieve different characteristics.
1.3.2.3 Interface
It has characteristics that are not depicted by any of the component in isolation.
The interface is a bounding surface or zone where a discontinuity occurs, whether
physical, mechanical, chemical etc. The matrix material must “wet” the fiber.
Coupling agents are frequently used to improve wettability. Well “wetted” fibers
increase the interface surfaces area. To obtain desirable properties in a composite, the
applied load should be effectively transferred from the matrix to the fibers via the
interface. This means that the interface must be large and exhibit strong adhesion
between fibers and matrix. Failure at the interface (called de-bonding) may or may not
be desirable.
1.4 TYPES OF COMPOSITE MATERIALS
The composite materials are broadly classified into the following categories as
shown in Figure-1.1
1.4.1 Fiber-reinforced composites
Reinforced-composites are popularly being used in many industrial applications
because of their inherent high specific strength and stiffness. Due to their excellent
structural performance, the composites are gaining potential also in tribological
applications. Fiber reinforced composites materials consists of fiber of high strength
and modulus in or bonded to a matrix with distinct interfaces (boundary) between
them [4, 5]. In this form both fibers and matrix retain their physical and chemical
identities. Yet they produce a combination of properties that cannot be achieved with
either of the constituents acting alone. In general, fibers are the principal load carrying
candidates, while the surrounding matrix keeps them in the desired location and
12
orientation [5, 6]. A Fibrous composite can be classified into two broad groups:
continuous (long) fiber composite and discontinuous (short) fiber composite.
1.4.1.1 Continuous or long fiber composite
Continuous or long fiber composite consists of a matrix reinforced by a dispersed
phase in the form of continuous fibers. A continuous fiber is geometrically
characterized as having a very high length-to- diameter ratio. They are generally
stronger and stiffer than bulk material. Based on the manner in which fibers are
packed within the matrix, it is again subdivided in to two categories: (a) unidirectional
reinforcement and (b) bidirectional reinforcement. In unidirectional reinforcement, the
fibers are oriented in one direction only where as in bidirectional reinforcement the
fibers are oriented in two directions either at right angle to one another (cross-ply), or
at some desired angle (angle-ply). When fibers are large and continuous, they impart
certain degree of anisotropy to the properties of the composites particularly when they
are oriented. Multi-axially oriented continuous fiber composites are also display near
isotropic properties.
1.4.1.2 Discontinuous or short fiber composite
Short-fiber reinforced composites consist of a matrix reinforced by a dispersed
phase in form of discontinuous fibers (length < 100×diameter). The low cost, ease of
fabricating complex parts, and isotropic nature are enough to make the short fiber
composites the material of choice for large-scale production. Consequently, the shortfiber reinforced composites have successfully established its place in lightly loaded
component manufacturing. Further the discontinuous fiber reinforced composite
divided into: (a) biased or preferred oriented fiber composite and (b) random oriented
fiber composite. In the former, the fibers are oriented in predetermined directions,
whereas in the latter type, fibers remain randomly. The orientation of short fibers can
be done by sprinkling of fiber on to given plane or addition of matrix in liquid or solid
state before or after the fiber deposition. The discontinuities can produce a material
response that is anisotropic, but the random reinforcement produces nearly isotropic
properties.
13
`
(a) Continuous fiber
composite
(b) Particulate
composite
(d) Random fiber (short fiber)
composite
(c) Flake composites
(e) Laminate Composite
Figure-1.1 Schematic diagram of different types of Composite
1.4.2 Laminate Composites
Laminate Composites are composed of layers of materials held together by matrix.
Generally, these layers are arranged alternatively for the better bonding between
reinforcement and the matrix. These laminates can have unidirectional or bidirectional orientation of the fiber reinforcement according to the end use of the
composite. Composite laminates are of different types such as unidirectional, angleply, cross-ply and symmetric laminates. A hybrid laminate can also be fabricated by
the use of different constituent materials or of the same material with different
reinforcing pattern. In most of the applications of laminate composites, man-made
fibers are used due to their good combination of physico-mechanical and thermal
behavior.
14
1.5 THESIS OUTLINE
The remainder of this thesis is organized as follows:
Chapter 2: Previous work relevant to the present investigations available in
literatures is described.
Chapter 3: This chapter describes the details of materials required, fabrication
techniques and the results from the tests for mechanical properties and
erosion wear behavior of the developed composite.
Chapter 4: In this chapter the fiber surface modification by chemical methods
namely, acetone and alkali has been carried out. The improvement in the
mechanical and erosion wear behavior after fiber treatment has been
reported.
Chapter 5: Conclusions from the above work has been drawn and recommendations
and scope for future work are presented in this chapter.
15
Chapter-2
2.1 LITERATURE SURVEY
Literature survey is carried out to get the background information on the issues to
be considered in the present research work and to focus the relevance of the present
study. The purpose is also to present a thorough understanding of various aspects of
natural fiber polymer composite with a special attention to their mechanical properties
and erosion wear behavior.
2.2 NATURAL FIBERS: Initiative in Product Development.
In fiber reinforced polymer composites, the fibers can be either synthetic fibers or
natural fibers. Natural fibers constituents are mainly of cellulose fibers, consisting of
helically wound cellulose micro fibrils, bound together by an amorphous lignin
matrix. Lignin keeps the water in fibers; acts as a protection against biological attack
and as a stiffener to give stem its resistance against gravity forces and wind.
Hemicellulose found in the natural fibers is believed to be a compatibilizer between
cellulose and lignin [9].The use of lignocellulosic fibers as reinforcements for
polymeric materials has been growing during the last decade or so to replace synthetic
fibers, especially glass fibers in composites, for different industrial sectors, such as
packaging, automobiles [10, 11] and even in the building sector [12]. This is mainly
due to their unique characteristics, such as availability, biodegradability, low density,
non-toxic nature, less abrasiveness to plastic processing equipment, useful mechanical
properties and low cost [13]. The physical mechanical properties of natural fibers are
greatly influenced by their chemical compositions. The properties of some of these
fibers are presented in Table-2.1 [14]. It is evident from Table-2.1 that, the tensile
strength of glass fiber is substantially higher than that of natural fibers even though
the modulus is of the same order. However, when the specific modulus of natural
fibers is considered, the natural fibers are better as compared to glass fibers.
Therefore, these higher specific properties are the major advantages of natural fiber as
reinforcement in polymer composites for weight sensitive applications.
16
Table 2.1 Properties of natural fibers [14]
Fiber
Tensile strength
(MPa)
Young’s
modulus (GPa)
Elongation at
break (%)
Density
(g/cm3)
Abaca
400
12
3-10
1.5
Alfa
350
22
5.8
0.89
Bagasse
290
17
-
1.25
Bamboo
140-230
11-17
-
0.6-1.1
Banana
500
12
5.9
1.35
Coir
175
4-6
30
1.2
Cotton
287-597
5.5-12.6
7-8
1.5-1.6
Curaua
500-1,150
11.8
3.7-4.3
1.4
Palm
97-196
2.5-5.4
2-4.5
1-1.2
Flax
345-1,035
27.6
2.7-3.2
1.5
Hemp
690
70
1.6
1.48
Henequen
500±70
13.2 ± 3.1
4.8 ± 1.1
1.2
Isora
500-600
-
5-6
1.2-1.3
Jute
393-773
26.5
1.5-1.6
1.3
Kenaf
930
53
1.6
-
Nettle
650
38
1.7
-
Oil palm
248
3.2
25
0.7-1.55
Piassava
134-143
1.07-4.59
21.9-7.8
1.4
Pineapple
400-627
1.44
14.5
0.8-1.6
Ramie
560
24.5
2.5
1.5
Sisal
511-635
9.4-22
2.0-2.5
1.5
E-Glass
3400
72
-
2.5
Natural organic fibers can be derived from either animal or plant sources. The
majority of useful natural textile fibers are plant derived, with the exceptions of wool
and silk. All plant fibers are composed of cellulose, whereas fibers of animal origin
consist of proteins. Natural fibers in general can be classified based on their origin,
and the plant-based fibers can be further categorized based on part of the plant they
are recovered from. An overview of natural fibers is presented in Figure-2.1 [15].
17
Figure-2.1: Overview of natural fiber [15].
A great deal of work has already been done on the effect of various factors on
mechanical behavior of natural fiber reinforced polymer composites. The post-impact
behavior of jute fiber reinforced polyester composites subjected to low velocity
impact has been studied by Santulli [16]. Effect of fiber content on tensile and
flexural properties of pineapple fiber reinforced poly (hydroxybutyrate-co-valerate)
resin composites has studied by Luo and Netravali [17].The mechanical behavior of
jute and kenaf fiber reinforced polypropylene composites has been studied by
Schneider and Karmaker [18]. It is concluded from their study that jute fiber based
composites provides better mechanical properties than kenaf fiber based composites.
The effect of various loading rate on mechanical properties of jute/glass reinforced
epoxy based hybrid composites has studied by Srivastav et al. [19]. The mechanical
properties of jute fiber reinforced polyester composites were evaluated by Gowda et
al. [20]. It is reported from their study that jute fiber based composites have better
strengths as compared to wood based composites. The limited use of natural fiber
composites is also connected with some other major disadvantages still associated
18
with these materials. Furthermore, the fibers inherent hydrophilic nature makes them
susceptible to water uptake in moist conditions. Natural fiber composites tend to swell
considerably with water uptake and as a consequence mechanical properties, such as
stiffness and strength, are negatively influenced. However, the natural fiber is not
inert. The fiber-matrix adhesion may be improved and the fiber swelling reduced by
means of chemical, enzymatic or mechanical modifications [21].
S.K.Acharya et al. [22] studied the influence of fiber treatment on the
performance of bagasse fiber reinforced polymer composite by different chemical
treatments. They reported considerable improvement on the mechanical properties of
the composite. Their report states that the shear stress of the composite is very
sensitive to the treatments. The shear stress decreases with increasing in fiber weight
fraction.
During the last few years, a series of works have also been done to replace the
conventional synthetic fiber with natural fiber composites [23, 24, 25-30].
Nevertheless, certain aspects of natural fiber reinforced composite behavior is still
poorly understood such as their visco elastic, visco plastic or time-dependent behavior
due to creep and fatigue loadings [31], interfacial adhesion [32, 33], and tribological
properties. Hashmi et al.[34] investigated the sliding wear behavior of cotton–
polyester composites and obtained better wear properties on addition of cotton
reinforcement. Tong et al. [35] studied the abrasive wear behavior of bamboo and
reported that the abrasive resistance of a bamboo stem is affected by the vascular
bundle fiber orientation with respect to the abrading surface and the abrasive particle
size. Recently, Chand and Dwivedi [36] report that the maleic-anhydride-grafted
polypropylene improved the wear properties of jute–polypropylene composites. In
another paper, they studied the tribological behavior of Wood Flour loading on epoxy
composites [37], and found that Wood Flour loading increases the load carrying
capacity of epoxy and decrease its wear resistance. Tayeb [38] reports the tribopotential of sugarcane fiber reinforcement in the thermoset polymers for enhancing
the adhesive wear resistance. Likewise rice husk has also considerable potential as
reinforcement for polymer and may provide advantage when used as a substitute for
conventional synthetic fiber. Recently Navin chand et al [39] studied the positive
effect of rice husk reinforcement as well as surface treatment on tribological and
mechanical properties of the resulting PVC-based composite.
19
In another work vinay kumar et al [40] reports that Polymer composites based on
rice husk and polypropylene can be made by compression or an injection molding
process. The amount of rice husk that can be utilized up to 40–60% resulting in
significant reduction in cost but higher amounts can cause handling and
agglomeration problems.
The conclusions drawn from this is that, the success of combining rice husk with
polymer matrices results in the improvement of mechanical properties of the
composites compared with the matrix materials. These fillers are cheap and nontoxic,
can be obtained from renewable sources, and are easily recyclable. Moreover, despite
their low strength, they can lead to composites with high specific strengths because of
their low density.
2.3 OBJECTIVE OF THE RESEARCH WORK
The priority of this work is to prepare polymer Matrix Composites (PMCs) using
rice husk (waste from rice mill industry) as reinforcement material. In the present
work two series of composites were prepared using randomly oriented unmodified
and modified rice husk as reinforcement in epoxy matrix. The composite are prepared
with different concentration of rice husk and the erosive wear behavior and
mechanical properties of the composites has been studied with different fiber loading.
Figure-2.2: Photograph of Rice Husk
20
Chapter-3
3.1 INTRODUCTION
Wear is a characteristic of the engineering system which depends on load, speed,
temperature, hardness, presence of foreign material and the environmental condition
[41]. Widely varied wearing conditions cause wear of materials. It may be due to
surface damage or removal of material from one or both of two solid surfaces in a
sliding, rolling or impact motion relative to one another. In most cases wear occurs
through surface interactions at asperities. During relative motion, material on
contacting surface may be removed from a surface, may result in the transfer to the
mating surface, or may break loose as a wear particle. The wear resistance of
materials is related to its microstructure may take place during the wear process and
hence, it seems that in wear research emphasis is placed on microstructure [42]. Wear
of material depends on many variables, so wear research program must be planned
systematically. Therefore researchers have normalized some of the data to make them
more useful. The wear map proposed by Lim [43] is very much useful in this regard
to understand the wear mechanism in different sliding conditions as well as the
anticipated rates of wear.
3.2 THEORY OF WEAR
Wear occurs as a natural consequence when two surfaces with a relative motion
interact with each other. Wear may be defined as the progressive loss of material from
contacting surfaces in relative motion. Scientists have developed various wear
theories in which the Physico-Mechanical characteristics of the materials and the
physical conditions (e.g. the resistance of the rubbing body and the stress state at the
contact area) are taken in to consideration. In 1940 Holm [44] starting from the
atomic mechanism of wear, calculated the volume of substance worn over unit sliding
path.
Barwell and Strang [45] in 1952: Archard [46] in 1953 and Archard and Hirst [47]
in 1956 developed the adhesion theory of wear and proposed a theoretical equation
identical in structure with Holm’s equation. In 1957, Kragelski [48] developed the
fatigue theory of wear. This theory of wear has been widely accepted by scientists in
different countries. Because of the Asperities in real bodies, their interactions in
21
sliding is discrete, and contact occurs at individual locations, which, taken together,
form the real contact area. Under normal force the asperities penetrate into each other
or are flattened out and in the region of real contact points corresponding stress and
strain rise. In sliding, a fixed volume of material is subjected to the many times
repeated action, which weakens the material and leads finally to rupture. In 1973,
Fleischer [49] formulated his energy theory of wear. The main concept of this theory
is that the separation of wear particles requires that a certain volume of material
accumulates a specific critical store of internal energy. It is known that a large part of
the work done in sliding is dissipated as heat, and that a small proportion of it
accumulates in the material as internal potential energy. When the energy attains a
critical value, plastic flow of the material occurs in this volume or a crack is formed.
Further theories of wear are found in [48]. Though all the theories are based on
different mechanisms of wear, the basic consideration is the frictional work.
With regards to the usage of natural fiber as reinforcement for tribological
application in polymeric composite, few works have been attempted. However, in
recent years, some work has been done on natural fiber like jute [50], cotton [51, 52],
oil palm [53], coir [54], kenaf [55], betel-nut [56], betel palm [57], wood flour [58]
and bamboo powder [59] as reinforcement. In these works, the wear resistance of
polymeric composites has been improved when natural fiber introduced as
reinforcement.
3.3 TYPES OF WEAR
Wear may be classified as:(1) Abrasive (2) Adhesive (3) Erosive (3) Surface fatigue (4) Corrosive
3.3.1 Abrasive wear
Abrasive wear may be defined as the wear that occurs when a hard surface slides
against and cuts groove from a softer surface. It can be account for most failures in
practice. Hard particles or asperities that cut or groove one of the rubbing surfaces
produce abrasive wear. This hard material may be originated from one of the two
rubbing surfaces. In sliding mechanisms, abrasion can arise from the existing
asperities on one surface (if it is harder than the other), from the generation of wear
fragments which are repeatedly deformed and hence get work hardened for oxidized
until they became harder than either or both of the sliding surfaces, or from the
22
adventitious entry of hard particles, such as dirt from outside the system. Two body
abrasive wear occurs when one surface (usually harder than the second) cuts material
away from the second, although this mechanism very often changes to three body
abrasion as the wear debris then acts as an abrasive between the two surfaces.
Abrasives can act as in grinding where the abrasive is fixed relative to one surface or
as in lapping where the abrasive tumbles producing a series of indentations as
opposed to a scratch. According to the recent tribological survey, abrasive wear is
responsible for the largest amount of material loss in industrial practice [60].
Figure-3.1 : Schematic representations of the abrasion wear mechanism
3.3.2 Adhesive wear
Adhesive wear can be defined as the wear due to localized bonding between
contacting solid surfaces leading to material transfer between the two surfaces or the
loss from either surface. For adhesive wear to occur it is necessary for the surfaces to
be in intimate contact with each other. Surfaces, which are held apart by lubricating
films, oxide films etc. reduce the tendency for adhesion to occur.
Figure-3.2: Schematic representations of the adhesive wear mechanism
3.3.3 Erosive wear
Erosive wear can be defined as the process of metal removal due to impingement
of solid particles on a surface. Erosion is caused by a gas or a liquid, which may or
may not carry, entrained solid particles, impinging on a surface. When the angle of
impingement is small, the wear produced is closely analogous to abrasion. When the
23
angle of impingement is normal to the surface, material is displaced by plastic flow or
is dislodged by brittle failure.
Figure-3.3: Schematic representations of the erosive wear mechanism
3.3.4 Surface fatigue wear
Wear of a solid surface is caused by fracture arising from material fatigue. The
term ‘fatigue’ is broadly applied to the failure phenomenon where a solid is subjected
to cyclic loading involving tension and compression above a certain critical stress.
Repeated loading causes the generation of micro cracks, usually below the surface, at
the site of a pre-existing point of weakness. On subsequent loading and unloading, the
micro crack propagates. Once the crack reaches the critical size, it changes its
direction to emerge at the surface, and thus flat sheet like particles is detached during
wearing. The number of stress cycles required to cause such failure decreases as the
corresponding magnitude of stress increases. Vibration is a common cause of fatigue
wear.
Figure-3.4: Schematic representations of the surface fatigue wear mechanism
3.3.5 Corrosive wear
Most metals are thermodynamically unstable in air and react with oxygen to form
an oxide, which usually develop layer or scales on the surface of metal or alloys when
their interfacial bonds are poor. Corrosion wear is the gradual eating away or
deterioration of unprotected metal surfaces by the effects of the atmosphere, acids,
24
gases, alkalis, etc. This type of wear creates pits and perforations and may eventually
dissolve metal parts.
3.4 SYMPTOMS OF WEAR
A summary of the appearance and symptoms of different wear mechanism is
indicated in Table–3.1 and the same is a systematic approach to diagnose the wear
mechanisms.
Table-3.1 Symptoms and appearance of different types of wear [61].
Types of
wear
Symptoms
Appearance of the worn
out surface
Abrasive
Presence of clean furrows cut out by
abrasive particles.
Grooves
Adhesive
Metal transfer is the prime symptoms.
Seizure, catering rough and
torn-out surfaces.
Erosion
Presence of abrasives in the fast moving
fluid and short abrasion furrows.
Waves and troughs.
Corrosion
Presence of metal corrosion products.
Rough pits or depressions.
Fatigue
Presence of surface or subsurface cracks
accompanied by pits and spalls.
Sharp and angular edges
around pits.
Impacts
Surface fatigue, small sub-micron particles
or formation of spalls.
Fragmentation, peeling and
pitting.
Delamination
Presence of subsurface cracks parallel to
the surface with semi-dislodged or loose
flakes.
Loose, long and thin sheet like
particles
Fretting
Production of voluminous amount of loose
debris.
Roughening, seizure and
development of oxide ridges
Electric attack
Presence of micro craters or a track with
evidence of smooth molten metal.
Smooth holes
25
Literature available on the rate of controlling abrasive wear mechanism
demonstrates that it may change abruptly from one another at certain sliding velocities
and contact loads, resulting in abrupt increases in wear rates. The conflicting results in
the abrasive wear literature arise partly because of the differences in testing
conditions, but they also make clear that a deeper understanding of the abrasive wear
mechanism is required if an improvement in the wear resistances of the polymer
matrix composites is to be achieved. This in turn requires a systematic study of the
wear under different loads and velocities. It is generally recognized that abrasive wear
is a characteristic of a system and is influenced by many parameters. Laboratory scale
investigation if designed properly allows careful control of the tribo system whereby
the effects of different variables on wear behavior of PMCs can be isolated and
determined. The data generated through such investigation under controlled
conditions may help in correct interpretation of the results.
As new developments are still under way to explore innovative fields for triboapplication of natural fiber base materials, in this chapter an attempt has been made to
study the potential of using rice husk fiber for tribological and mechanical
applications. In the current study the effect of fiber loading, sliding velocity, sliding
distance and normal load on abrasive wear behavior of rice husk fiber filled epoxy
composite has been evaluated and possible wear mechanism has been discussed with
SEM observation.
3.5 FABRICATION OF COMPOSITES
For preparation of composites to conduct mechanical and wear test the following
materials has been used;
 Rice husk fibers
 Epoxy
 Hardner
3.5.1 Rice husk
Rice husk (RH) is an agricultural waste material abundantly available in riceproducing countries. They are the natural sheaths that form on rice grains during their
growth and removed during the refining of rice, these husks have no commercial
interest. Rice husk is a fibrous material and has a varied range of aspect ratio. Thus it
can be used as filler for making light weight polymer composites. Keeping this in
26
view the present work has been under taken to develop a polymer matrix composite
(epoxy resin).
3.5.2 Epoxy Resin & Hardner
The type of epoxy resin used in the present investigation is Araldite LY-556
which chemically belongs to epoxide family. Its common name is Bisphinol-ADiglycidyl-Ether. The hardener with IUPAC name NNO-bis (2aminoethylethane1,2diamin) has been used with the epoxy designated as HY 951. Both the epoxy and
hardener were supplied by Ciba Geigy of India Ltd.
3.6 FABRICATION & PREPARATION OF COMPOSITE SLABS
The Rice husks were collected locally. They were washed several times with plain
water to remove the dust and other foreign particles adherence to the fibers and were
dried in sun light. Then these rice husk fibers sieved with sieve shaker and a particular
size (i.e. 2.36mm) rice husk fiber is chosen for the experiment.
Usual hand lay-up technique was used for preparation of the samples. A plastic
mold of dimension (140x100x6) mm was used for casting the composite sheet
(Fig.3.5). A mold release spray was applied at the inner surface of the mold for quick
and easy release of the composite sheet. For different weight fraction of fibers, a
calculated amount of epoxy resin and hardener (ratio of 10:1 by weight) was
thoroughly mixed in a glass jar and placed in a vacuum chamber to remove air
bubbles that got introduced. Then calculated amount of rice husk is added to the
mixture of epoxy resin and hardner and mixed properly. Then the composite mixture
is poured in to the mold.
Care has been taken to avoid formation of air bubbles. Pressure was then applied
from the top and the mold was allowed to cure at room temperature for 72 hrs. During
application of pressure some amount of epoxy and hardener squeezes out. Care has
been taken to consider this loss during manufacturing so that a constant thickness of
sample can be maintained. This procedure was adopted for preparation of 5, 10, 15
and 20% weight fractions of fiber reinforced epoxy composite slabs. After 72 hrs the
samples were taken out from the mold and then cut in to required sizes as per ASTM
standards for Mechanical test.
27
(a)
(b)
(c)
Figure-3.5: (a) Mold used for composite preparation (b) Specimen cut for bend
test (c) Specimen cut for erosion test.
3.7 TENSILE TEST
The standard test method according to ASTM D3039-76 has been used; gauge
length of the test specimen used is 50 mm. The tensile test has been performed in
universal testing machine INSTRON H10KS .The test was conducted with a cross
head speed of 5mm/min. For each test, composite of five samples were tested and
average value was taken for analysis. Figure 3.6 shows the Machine used for the test
and the sample in loading condition. The results obtained from the tests are presented
in Table-3.2. Tensile strength & Young’s modulus were found out using the following
formula.
28
𝜎=
𝑃
………………… (3.1)
𝐸=
𝜎𝐿
..……………… (3.2)
𝐴
𝛿
Where ‘σ’ is tensile strength, ‘P’ is the load applied, ‘A’ is the cross sectional
area, ‘E’ is Young’s modulus, ‘L’ is span length of the specimen and ‘δ’ is the
deflection recorded.
Figure-3.6: INSTRON H10KS TESTING MACHINE
3.8 BEND TEST
Three point bend test was carried out in an UTM 201 machine in accordance with
ASTM D2344-84 to measure the flexural strength of the composites. The loading
arrangement for the specimen and the photograph of the machine used are shown in
Figure-3.7(a) and (b) respectively. All the specimens (composites) were of rectangular
shape having length varied from 100-125 mm, breadth of 20-25 mm and thickness of
3.5-5.0 mm. A span of 100 mm was employed maintaining a cross head speed of
5mm/min. The flexural strength in a three point bending test is found out by using
equation (3.3). The flexural strength of composites was found out using the following
equation
29
𝐹𝑆 =
𝐺=
3𝑃𝐿
……………………. (3.3)
3𝑃𝐿3
..………………….. (3.4)
2𝑏𝑡 2
4𝑏𝑡 3 𝑦
Where ‘b’ is breadth, ‘t’ is thickness and ‘y’ is extension of the specimen during
experiment.
(a)
(b)
Figure-3.7: Loading position of specimen for bend test
3.9 RESULTS OF TENSILE TEST AND BEND TEST
The tensile strength results for various specimens were plotted in figure 3.8.Plot
shows that, with increase of fiber concentration the tensile strength goes on increasing
and samples with 15% fiber weight fraction gives maximum strength.
Figure 3.9 shows the variation in flexural strength for neat epoxy and different
weight fraction of fiber composites. The flexural strength results for different weight
30
fraction of fiber composite has also follow the same trend as for the tensile strength
and have a maximum value for 15% weight fraction of fiber.
Table-3.2 Mechanical properties of PRH reinforced epoxy & Neat Epoxy
composites.
Fiber content by weight Tensile Strength (MPa) Flexural Strength (MPa)
0%
14.07
18.18
5%
15.37
19.55
10%
17.81
20.29
15%
18.52
22.88
20%
15.55
18.75
Tensile Strength (MPa)
21
17.81
18
15
14.07
18.52
15.55
15.37
12
9
6
3
0
Epoxy
5%
10%
15%
20%
Plain Rice Husk & Epoxy
Figure-3.8: Variation of tensile strength with increasing weight % of rice husk
reinforcement in the composite.
31
Flexural Strength (MPa)
25
20
22.88
18.18
19.55
20.29
5%
10%
18.75
15
10
5
0
Epoxy
15%
20%
Plain Rice Husk & Epoxy
Figure-3.9: Variation of flexural strength with increasing weight % of rice husk
reinforcement in the composite.
3.10 SOLID PARTICLE EROSION TEST
Solid particle erosion manifests itself in thinning of components, surface
roughening, surface degradation, macroscopic scooping appearance and reduction in
functional life of the structure. Hence, solid particle erosion has been considered as a
serious problem as it is responsible for many failures in engineering applications.
Several attempts to understand the basic mechanisms of the erosion were started in
the last half of the 20th century and have been continued to the present. In the year of
1995 an article on the past and the future of erosion was presented by Finnie [62]. In
this article, the influencing parameters and dominating mechanisms during solid
particle erosion were reviewed on the erosion response of metals and ceramic
materials. In the same year another article was published by Meng et al. [63] to
provide information about the existing wear models and prediction equations.
The subject of erosion wear of polymer composite has received substantial
attention in the past decades. Interest in this area is commensurate with the increasing
utilization of polymer based composites in aerospace, transportation and processing
industries, where they can be subjected to multiple solid or liquid particle impact.
Examples of such applications are pipe lines carrying sand slurries in petroleum
refining, helicopter rotor blades , pump impeller blades, high speed vehicles and
aircraft operating in desert environments, radomes, surfing boats where the
32
component encounter impact of lot of abrasives like dust, sand, splinters of materials,
slurry of solid particle and consequently the materials undergo erosive wear [64-66].
Many researchers have evaluated the resistance of various types of polymers
like nylon, epoxy, polypropylene, bismileimide, etc and their composites to solid
particle erosion. Harsha et al. [67] has summarized the work done by some of the
investigators on solid particle erosion of polymer composites. Roy et al. while
working on erosive wear of polymer composite revealed that the composite materials
present a rather poor erosion resistance as compared to metallic materials [68].
Biswas et al. [69] worked on red mud filled glass epoxy composite and explained the
ductile and brittle behavior criteria of the composite based on the impact angle of
erosion wear.
The most important factors influencing the erosion rate of the composite
materials can be summarized under four categories; (i) The properties of the target
materials (matrix material properties and morphology, reinforcement type, amount
and orientation, interface properties between the matrices and reinforcements, etc.),
(ii) Environment and testing conditions (temperature, chemical interaction of erodent
with the target), (iii) Operating parameters (angle of impingement, impinging
velocity, particle flux–mass per unit time, etc.) and (iv ) The properties of the erodent
(size, shape, type, hardness, etc.) [66, 70-72]. The ductile behavior is characterized by
maximum erosion at low impact angle in the range of 15°–30°. On the other hand, if
maximum erosion occurs at 90°, then the behavior can be termed as brittle.
Reinforced composites have also been some time found to exhibit an intermediate
behavior known as semi-ductile with maximum erosion occurring at an angle in the
range of 45°–60° [73]. However, the above classification is not absolute as the erosion
behavior of a material has a strong dependence on erosion conditions such as impact
angle, impact velocity and erodent properties such as shape, hardness, size etc. In the
literature, the erosion behavior of polymers and its composites has also been
characterized by the value of the velocity exponent, ‘n’ (Er α vn) [64].
3.11 EXPERIMENT
3.11.1 Preparation for the test specimens
The preparation of the test specimens were carried out as per the procedure
discussed in Art-3.5. Specimens of dimension 30 x 30 x 3.0 mm were cut from the
33
composite slabs. Adequate care has been taken to keep the thickness constant (3mm)
for all the samples.
3.11.2 Test apparatus & Experiment
The schematic figure of the erosion test apparatus used for the present
investigation designed as per ASTM-G76 standard is shown in Figure-3.10. The rig
consists of an air compressor, a particle feeder, and an air particle mixing and
accelerating chamber. The compressed dry air is mixed with the erodent particles,
which are fed at a constant rate from a conveyor belt-type feeder in to the mixing
chamber and then accelerated by passing the mixture through a tungsten carbide
converging nozzle of 4 mm diameter. These accelerated particles impact the
specimen, and the specimen could be held at various angles with respect to the
impacting particles using an adjustable sample holder. The test apparatus has also
been fitted with a rotating double disc to measure the velocity of the erodent particle.
The impact velocities of the erodent particles has been evaluated experimentally
using this rotating double disc method developed as explained by Ives and Ruff [74].
The velocities obtained from this method for various pressures are given in Table-3.3.
The conditions under which the erosion test has been carried out are given in
Table-3.4. A standard test procedure is employed for each erosion test. The samples
are cleaned in acetone, dried and weighed to an accuracy of 1×10-3 gm using an
electronic balance, prior and after each test. The test samples after loading in the test
rig were eroded for 1 min. at a given impingement angle and then weighed again to
determine weight loss (∆w). The erosion rate (Er) is then calculated by using the
following equation:
𝐸𝑟 =
∆𝑤
𝑤𝑒
.……………… (3.5)
Where Δw is the mass loss of test sample in gm and we is the mass of eroding
particles (i.e., testing time × particle feed rate). This procedure has been repeated until
the erosion rate attains a constant steady-state value. In the present study the same
procedure is repeated for 5 times (i.e. expose time was 5min).
The erosion efficiency (η) for the process was obtained by using the equation:
34
𝜂=
2𝐸𝑟 𝐻
𝜌×𝑣 2
……………… (3.6)
Where ‘Er’ is erosion rate (kg/kg), ‘H’ is hardness of eroding material (MPa) and
‘v’ is velocity of impact (m/s), proposed by Sundararajan et al. [75]. Experimental
results of the erosion test for different weight fraction of Rice-Husk fiber reinforced
epoxy composites with different impingement angle and velocities are tabulated and
presented in table-3.5 to 3.9.
3.12 RESULTS & DISCUSSION
Based on the tabulated results various graphs were plotted and presented in
Figure-3.11 to 3.14 for different percentage of reinforcement under different test
conditions.
Figure-3.11 to 3.14 illustrate the erosion wear rates of both neat epoxy and RH
reinforced epoxy composite as a function of impingement angle under different
impact velocities (48m/s to 109m/s). It is observed that Rice-Husk fiber epoxy
composite of different % wt. fraction and also neat epoxy shows peak erosion rate (Er
max) at 45° and 60° impact angle and minimum erosion rate (Er min) at normal
incidence (90°) under all velocity of impact. It has been observed that for ductile
material maximum erosion exists at low impact angles (15 ° to 30 °) whereas for
brittle materials it is at normal angle (90°) [76]. Hence the maximum erosion
occurring between 45° to 60° angles shows semi-ductile or semi-brittle material [77].
From the experimental results it is clear that RH fiber reinforced composites respond
to solid particle impact neither behaves in a purely ductile nor in a purely brittle
manner. This behavior can be termed as semi-brittle in nature. It is further observed
that irrespective of impact velocity and impact angle, the erosion rate is highest for
neat epoxy whereas erosion rate decreases to minimum as the % wt. fraction of fiber
increases and the optimum value was found in 20% wt. fraction of Rice-Husk fiber
reinforced epoxy composite.
The variation of steady-state erosion rate of all composite samples with impact
velocity at different impact angles are shown in the form of a histogram in Figure3.15 to 3.18. It can be observed from these histograms that erosion rate of all
composite samples increases with increase in the impact velocity. However, 20% wt.
fraction shows the least variation in the erosion rate with increase in the impact
35
velocity at low impact angle (α = 30°). Irrespective of impingement angle and impact
velocity, there is a steady decrease in erosion rate with increase in fiber content has
also been observed. This indicates that the erosion rate of composites is decreased
only by the increased weight fraction of fiber content.
In the solid particle impact experiments the impact velocity of the erosive particles
has a very strong effect on erosion rate. For any material, once steady state conditions
have reached, the erosion rate ‘Er’ can be expressed as a simple power function of
impact velocity (v) [64]:
Er=kvn
…………………. (3.7)
where k is the constant of proportionality includes the effect of all the other
variables and ‘n’ is the velocity exponent. The value of ‘n’ and ‘k’ are found by leastsquare fit ing of the data points in plots which represent the erosion rate dependence
on impact velocity by using the power law. The value of ‘n’ is typically between 2
and 4, although much higher exponent is seen under some circumstances [68].
According to Pool et al. [64], for polymer composites behaving in ductile manner, the
velocity exponent ‘n’ varies in the range 2-3 while for polymer composites behaving
in brittle fashion the value of ‘n’ should be in the range of 3-5. Figure-3.19 to 3.22
illustrates the variation of erosion rate with impact velocities at different impingement
angle for neat epoxy and its composites. The least-square fits to data point were
obtained by using power law and the values of ‘n’ and ‘k’ are summarized in Table3.6. The velocity exponents found for 30°, 45°, 60° and 90° impingement angles are
in the range of 2.56-2.91, 2.53-2.70, 2.94-3.11 and 2.91-3.05 respectively. The value
of velocity exponent ‘n’ shows that Rice-Husk filled epoxy composite behaves in a
semi-brittle manner. This velocity exponent at various impingement angles are in
conformity with Harsha et al. [78].
It has been reported by Sundararajan et al. [68, 75] that the erosion efficiency (η),
can be used to characterize the nature and mechanism of erosion. They also showed
that the ductile material possesses very low erosion efficiency i.e. η<<100%, whereas
the brittle material exhibits an erosion efficiency even greater than 100%. The values
of erosion efficiencies of composites under this study are calculated using equation3.2 and are listed in Table-3.11 & 3.12 along with their hardness values and operating
36
conditions. According to the categorization made by Roy et al. [68], it has been
observed that the erosion efficiencies of Rice-Husk fiber epoxy composite varies
from 1% to 5% for different impact velocities, indicating a semi-brittle erosion
response. Further it is noticed that the erosion efficiency of all tests sample slightly
increases with increase in impact velocity. Thus it can be conclude that the erosion
efficiency is not exclusively a material property; but also depends on other operational
variables such as impact velocity and impingement angle. The data shown in Table3.11 & 3.12 are also indicates that the erosion efficiency of Rice-Husk fiber epoxy
composite increase with increase in fiber content whereas the neat epoxy exhibits a
lower value under all testing condition. This lower erosion efficiency of neat epoxy
indicates a less erosion resistance in comparison to Rice-Husk fiber epoxy composite.
3.13 CONCLUSIONS
Based on the experimental results of mechanical test and abrasive wear test of
rice husk fiber reinforced epoxy composite, the following conclusions has been
drawn.
1.
The Plain Rice-Husk (PRH) fiber can successfully be used as reinforcing
agent to fabricate composite by suitably bonding with epoxy resin.
2.
With increasing rice husk fibers reinforcement the tensile strength and
flexural strength increases gradually and it is found that 15% weight
fraction of Plain Rice-Husk reinforcement gives better strength than
others.
3.
Fiber breakages are found to be the predominant mode of failure as
ascertained from the morphology of the treated fiber composites.
4.
The incorporation of rice husk in to epoxy can significantly reduce the
erosive wear loss. The optimal wear resistance property was obtained
at a fiber content of 20% weight fraction.
5.
The influence of impingement angle on erosive wear of composites
under consideration exhibits semi-brittle erosive wear behavior with
maximum wear rate between 45°-60° impingement angle.
6.
With increasing of the velocity of impingement, erosion rate gradually
increases.
37
7.
In PRH-epoxy composites the erosion rate (Er) displays power law
behavior with particle velocity (v), Er α vn , where ‘n’ varies from 2.53 to
3.11 which further explains its semi-brittle behavior.
8.
The erosion efficiency (η) values obtained experimentally also indicate
that the Plain Rice-Husk (PRH) fiber reinforced epoxy composites
exhibit semi-brittle erosion response (1.496%-5.442%).
9.
The morphologies of eroded surface of the samples observed by SEM
indicate that, material removal is mainly due to micro-cutting and
micro-ploughing.
38
Table-3.3: Particle velocity under different pressure.
S. No.
Air Pressure (Bar)
Particle velocity
(m/s)
1
1
48
2
2
70
3
3
82
4
4
109
Table-3.4: Experimental parameters for the erosion test.
Erodent
Silica sand
Erodent size (µm)
300-600
Impingement angle(α°)
30, 45, 60, 90
Impact velocity (m/s)
48, 70, 82, 109
Erodent feed rate (gm/min)
11
Test temperature
Room temperature
Standoff distance (mm)
10
Nozzle diameter (mm)
4
Time of experiment (min)
5
39
Table- 3.5: Cumulative weight loss & erosion rate of neat epoxy for a period of 5
minutes at different velocities and angles.
Velocity
(m/s)
48
70
82
109
Neat Epoxy
Angle
(degree)
Weight of
impingement
(gm)
Weight loss
(gm)
Erosion Rate
Er x 10-4
(gm/gm)
30
55
0.011
2.056
45
55
0.013
2.340
60
55
0.011
1.929
90
55
0.008
1.471
30
55
0.029
5.345
45
55
0.048
8.800
60
55
0.044
7.964
90
55
0.027
4.836
30
55
0.049
8.964
45
55
0.068
12.364
60
55
0.074
13.455
90
55
0.059
10.709
30
55
0.089
16.255
45
55
0.108
19.636
60
55
0.113
20.455
90
55
0.090
16.364
40
Table- 3.6: Cumulative weight loss & erosion rate of 5% PRH for a period of 5
minutes at different velocities and angles.
Velocity
(m/s)
48
70
82
109
PRH 5%
Angle
(degree)
Weight of
impingement
(gm)
Weight loss
(gm)
Erosion Rate
Er x 10-4
(gm/gm)
30
55
0.010
1.853
45
55
0.012
2.240
60
55
0.009
1.700
90
55
0.007
1.309
30
55
0.020
3.636
45
55
0.045
8.255
60
55
0.037
6.764
90
55
0.024
4.450
30
55
0.044
8.000
45
55
0.063
11.436
60
55
0.071
12.891
90
55
0.051
9.200
30
55
0.083
15.000
45
55
0.100
18.182
60
55
0.108
19.564
90
55
0.082
14.891
41
Table- 3.7: Cumulative weight loss & erosion rate of 10% PRH for a period of 5
minutes at different velocities and angles.
Velocity
(m/s)
48
70
82
109
PRH 10%
Angle
(degree)
Weight of
impingement
(gm)
Weight loss
(gm)
Erosion Rate
Er x 10-4
(gm/gm)
30
55
0.008
1.469
45
55
0.012
2.151
60
55
0.009
1.600
90
55
0.007
1.335
30
55
0.025
4.491
45
55
0.039
7.109
60
55
0.035
6.309
90
55
0.021
3.782
30
55
0.043
7.727
45
55
0.060
10.836
60
55
0.066
11.945
90
55
0.048
8.727
30
55
0.080
14.455
45
55
0.095
17.291
60
55
0.103
18.764
90
55
0.076
13.873
42
Table- 3.8: Cumulative weight loss & erosion rate of 15% PRH for a period of 5
minutes at different velocities and angles.
Velocity
(m/s)
48
70
82
109
PRH 15%
Angle
(degree)
Weight of
impingement
(gm)
Weight loss
(gm)
Erosion Rate
Er x 10-4
(gm/gm)
30
55
0.009
1.633
45
55
0.011
2.007
60
55
0.008
1.480
90
55
0.006
1.164
30
55
0.017
3.145
45
55
0.036
6.618
60
55
0.031
5.636
90
55
0.021
3.782
30
55
0.035
6.327
45
55
0.052
9.400
60
55
0.058
10.545
90
55
0.042
7.600
30
55
0.075
13.636
45
55
0.086
15.673
60
55
0.097
17.618
90
55
0.073
13.182
43
Table- 3.9: Cumulative weight loss & erosion rate of 20% PRH for a period of 5
minutes at different velocities and angles.
Velocity
(m/s)
48
70
82
109
PRH 20%
Angle
(degree)
Weight of
impingement
(gm)
Weight loss
(gm)
Erosion Rate
Er x 10-4
(gm/gm)
30
55
0.006
1.169
45
55
0.009
1.562
60
55
0.007
1.336
90
55
0.007
1.229
30
55
0.018
3.273
45
55
0.033
5.927
60
55
0.028
5.091
90
55
0.019
3.364
30
55
0.031
5.600
45
55
0.045
8.127
60
55
0.052
9.527
90
55
0.040
7.255
30
55
0.069
12.545
45
55
0.078
14.127
60
55
0.089
16.218
90
55
0.068
12.418
44
Table- 3.10: Parameters characterizing the velocity dependence of erosion rate of
Neat Epoxy & PRH reinforced composite.
Fiber Type
Neat Epoxy
PRH 5%
PRH 10%
PRH 15%
PRH 20%
Angle
(Degree)
k x 10-6
n
30
106
2.56
45
107
2.62
60
25
2.94
90
12
3.04
30
66
2.62
45
121
2.58
60
13
3.06
90
10
3.05
30
27
2.83
45
127
2.53
60
12
3.08
90
14
2.96
30
55
2.63
45
111
2.58
60
10
3.09
90
9
3.03
30
14
2.91
45
52
2.70
60
8
3.11
90
16
2.91
45
Table-3.11: Erosion efficiency (η) of neat epoxy samples.
Impact Velocity
(m/s)
48
70
82
109
Impact Angle
(Degree)
Neat Epoxy
H = 117.7 (MPa)
ρ =1140 (Kg/m3)
30
1.843
45
2.097
60
1.729
90
1.318
30
2.253
45
3.708
60
3.356
90
2.038
30
2.753
45
3.797
60
4.132
90
3.289
30
2.825
45
3.413
60
3.555
90
2.844
46
Table-3.12: Erosion efficiency (η) of PRH composite samples.
Impact
Velocity
(m/s)
48
70
82
109
PRH 5%
PRH 10%
PRH 15%
PRH 20%
Impact
Angle
(Degree)
H=149.1
(MPa)
ρ =1106
(Kg/m3)
H=159.9
(MPa)
ρ =1044
(Kg/m3)
H=167.7
(MPa)
ρ =1132
(Kg/m3)
H=181.4
(MPa)
ρ =1026
(Kg/m3)
30
2.168
1.953
2.100
1.794
45
2.621
2.860
2.581
2.397
60
1.989
2.127
1.903
2.051
90
1.532
1.774
1.496
1.886
30
2.001
2.807
1.902
2.362
45
4.542
4.444
4.002
4.277
60
3.722
3.944
3.408
3.674
90
2.449
2.364
2.287
2.427
30
3.208
3.520
2.788
2.945
45
4.586
4.937
4.142
4.274
60
5.169
5.442
4.647
5.010
90
3.689
3.976
3.349
3.815
30
3.404
3.727
3.401
3.734
45
4.126
4.458
3.908
4.205
60
4.440
4.838
4.394
4.827
90
3.379
3.577
3.287
3.696
47
Figure-3.10: Details of erosion test rig.
(1) Sand hopper (2) Conveyor belt system for sand flow (3) Pressure
transducer, (4) Particle-air mixing chamber, (5) Nozzle, (6) X–Y and
h axes assembly, (7) Sample holder.
48
2.6
48 m/s, PRH
Erosion Rate x 10-4
2.4
2.2
2.0
Neat Epoxy
1.8
PRH 5%
1.6
PRH 10%
1.4
PRH 15%
PRH 20%
1.2
1.0
15
30
45
60
75
90
Impingement Angle (degree)
Figure-3.11: Variation of erosion rate with impingement angle of various Plain
Rice-Husk epoxy composite at impact velocity of 48 m/s.
10.0
70 m/s, PRH
9.0
Erosion Rate x 10-4
8.0
7.0
Neat Epoxy
6.0
PRH 5%
5.0
PRH 10%
4.0
PRH 15%
3.0
PRH 20%
2.0
1.0
15
30
45
60
75
90
Impingement Angle (degree)
Figure-3.12: Variation of erosion rate with impingement angle of Epoxy & PRHepoxy composite at impact velocity of 70 m/s.
49
15.0
82 m/s, PRH
Erosion Rate x 10-4
13.0
11.0
Neat Epoxy
9.0
PRH 5%
7.0
PRH 10%
5.0
PRH 15%
3.0
PRH 20%
1.0
15
30
45
60
75
90
Impingement Angle (degree)
Figure-3.13: Variation of erosion rate with impingement angle of Epoxy & PRHepoxy composite at impact velocity of 82 m/s.
26.0
109 m/s, PRH
Erosion Rate x 10-4
21.0
Neat Epoxy
16.0
PRH 5%
11.0
PRH 10%
PRH 15%
6.0
PRH 20%
1.0
15
30
45
60
75
90
Impingement Angle (degree)
Figure-3.14: Variation of erosion rate with impingement angle of Epoxy & PRHepoxy composite at impact velocity of 109 m/s.
50
PRH, 30°
18
16
Erosion Rate x 10-4
14
12
48
8
70
6
82
4
109
2
0
5%
Neat
10%
PRH
15%
PRH
20%
PRH
PRH
48
70
Epoxy
82
109
10
Figure-3.15: Histogram showing the steady state erosive wear rates of all the
composites of PRH & epoxy at four impact velocities (i.e. at 48, 70, 82 and 109
m/s) for 30° impact angle.
PRH, 45°
20
Erosion Rate x 10-4
15
48
10
70
82
5
0
5%
Neat
10%
PRH
15%
PRH
20%
PRH
PRH
48
70
Epoxy
82
109
109
Figure-3.16: Histogram showing the steady state erosive wear rates of all the
composites of PRH & epoxy at four impact velocities (i.e. at 48, 70, 82 and 109
m/s) for 45° impact angle.
51
PRH, 60°
25
Erosion Rate x 10-4
20
15
48
70
10
82
5
0
5%
Neat
10%
PRH
15%
PRH
20%
PRH
PRH
48
70
Epoxy
82
109
109
Figure-3.17: Histogram showing the steady state erosive wear rates of all the
composites of PRH & epoxy at four impact velocities (i.e. at 48, 70, 82 and 109
m/s) for 60° impact angle.
PRH, 90°
18
16
Erosion Rate x 10-4
14
12
48
8
70
6
82
4
109
2
0
5%
Neat
10%
PRH
15%
PRH
20%
PRH
PRH
48
70
Epoxy
82
109
10
Figure-3.18: Histogram showing the steady state erosive wear rates of all the
composites of PRH & epoxy at four impact velocities (i.e. at 48, 70, 82 and 109
m/s) for 60° impact angle.
52
18
PRH & Epoxy, 30°
16
Neat Epoxy
PRH 5%
Erosion Rate x 10-4
14
PRH 10%
12
PRH 15%
10
PRH 20%
8
6
y = 1.06E-04x2.56
Power (Neat Epoxy)
y = 6.63E-05x2.62
Power (PRH 5%)
y=
4
2
2.72E-05x2.83
Power (PRH 10%)
y = 5.56E-05x2.63
Power (PRH 15%)
1.48E-05x2.91
Power (PRH 20%)
y=
0
45
65
85
105
Velocity (m/s)
Figure-3.19: Variation of steady-state erosion rate of neat epoxy and PRH-epoxy
composites as a function of impact velocity for 30° impact angle.
PRH & Epoxy, 45°
25
Neat Epoxy
PRH 5%
Erosion Rate x 10-4
20
PRH 10%
PRH 15%
15
PRH 20%
y=
10
1.07E-04x2.62
y = 1.21E-04x2.58
y=
5
Power (Neat Epoxy)
Power (PRH 5%)
1.27E-04x2.53
Power (PRH 10%)
y = 1.11E-04x2.58
Power (PRH 15%)
5.22E-05x2.70
Power (PRH 20%)
y=
0
45
65
85
105
Velocity (m/s)
Figure-3.20: Variation of steady-state erosion rate of neat epoxy and PRH-epoxy
composites as a function of impact velocity for 45° impact angle.
53
PRH & Epoxy, 60°
30
Neat Epoxy
Erosion Rate x 10-4
25
PRH 5%
PRH 10%
20
PRH 15%
PRH 20%
15
10
5
0
45
65
y = 2.54E-05x2.94
Power (Neat Epoxy)
y = 1.38E-05x3.06
Power (PRH 5%)
y=
1.20E-05x3.08
Power (PRH 10%)
y=
1.05E-05x3.09
Power (PRH 15%)
y=
8.71E-06x3.11
Power (PRH 20%)
85
105
Velocity (m/s)
Figure-3.21: Variation of steady-state erosion rate of neat epoxy and PRH-epoxy
composites as a function of impact velocity for 60° impact angle.
PRH & Epoxy, 90°
25
Neat Epoxy
Erosion Rate x 10-4
20
PRH 5%
PRH 10%
15
PRH 15%
PRH 20%
10
5
y = 1.21E-05x3.04
Power (Neat Epoxy)
y = 1.04E-05x3.05
Power (PRH 5%)
y = 1.44E-05x2.96
Power (PRH 10%)
y = 9.73E-06x3.03
Power (PRH 15%)
1.62E-05x2.91
Power (PRH 20%)
y=
0
45
65
85
105
Velocity (m/s)
Figure-3.22: Variation of steady-state erosion rate of neat epoxy and PRH-epoxy
composites as a function of impact velocity for 90° impact angle.
54
Chapter-4
4.1 INTRUDUCTION
In general natural fibers are hygroscopic in nature and they absorb or release
moisture depending on environmental conditions. Amorphous cellulose and
hemicellulose that present in the natural fiber are mostly responsible for the high
moisture absorption, since they contain numerous easily accessible hydroxyl groups
which give a high level of hydrophilic character to fiber. The high moisture
absorption of the fiber occurs due to hydrogen bonding of water molecules to the
hydroxyl groups within the fiber cell wall. This leads to a moisture build-up in the
fiber cell wall (fiber swelling) and also in the fiber-matrix interface. This in turn
becomes responsible for changes in the dimensions of cellulose-based composites,
particularly in the thickness and the linear expansion due to reversible and irreversible
swelling of the composites [60]. Another problem associated with fiber swelling is a
reduction in the adhesion between the fiber and the matrix, leading to deterioration in
the mechanical properties of the composite [61]. A good fiber-matrix bonding can
decrease the rate and amount of moisture absorbed by the composite as well as
improving the mechanical properties [79]. However in order to overcome this
problem, chemical treatment has been considered as a good technique to reduce the
hydroxyl group in the fibers.
4.2 CHEMICAL MODIFICATIONS OF FIBERS
The main disadvantages of natural fibers in composites are the poor compatibility
between fiber and matrix and the relative high moisture absorption. Therefore a better
understanding of the chemical composition and surface adhesive bonding of natural
fiber is necessary for developing natural fiber reinforced composites.
The chemical treatment of natural fibers aimed at improving the adhesion between
the fiber surface and the polymer matrix which can modify the fiber surface and also
increases fiber strength. Moisture absorption of the composites can be reduced and
their mechanical properties can be improved. In this experiment RH is chemically
treated with Alkali and Acetone for better fiber and matrix interaction. Chemical
treatment also helps to remove wax, silicon and other impurities [80].
55
4.3 METHODS OF CHEMICAL MODIFICATIONS
4.3.1 Acetone Treatment
Acetone treatment of natural fiber washes out some amount of cellulolignin, lignin
and impurities of the fiber surface such as wax and dust content. Acetone is a nonpolar organic solvent which usually dissolves the non-polar organic component hence
increasing the fiber adhesion with the epoxy matrix.
The reaction involves the generation of acetic acid (CH3COOH) as by-product
which must be removed from the lignocellulosic material before the fiber is used.
Chemical modification with acetic anhydride (CH3-C(=O)-O-C(=O)-CH3) substitutes
the polymer hydroxyl groups of the cell wall with acetyl groups, modifying the
properties of these polymers so that they become hydrophobic . The reaction of acetic
anhydride with fiber is shown as.
Fiber-OH + CH3-C (=O)-O-C (=O)-CH3→Fiber-OCOCH3+CH3COOH
Acetylation can reduce the hygroscopic nature of natural fibers and increases the
dimensional stability of composites. Acetylation was used in surface treatments of
fiber for use in fiber-reinforced composites
4.3.2 Alkali Treatment
Alkali treatment of cellulosic fibres with sodium hydroxide (NaOH) is one of such
methods that have been employed in order to improve the fiber–matrix interface
bonding. This treatment removes wax, oils covering, some amount of lignin and the
silicon content of the external surface of the RH fiber cell wall. It also depolymerizes
cellulose and exposes it to the matrix.
-
+
Fiber – OH + NaOH → Fiber – O Na +H2O
It is reported that alkaline treatment has two effects on the natural fiber: (1) it
increases surface roughness resulting in better mechanical interlocking; and (2) it
increases the amount of cellulose exposed on the fiber surface to the matrix, which
increases the number of possible reaction sites [81].
56
4.3.3 Benzoyl Chloride Treatment
Benzoyl chloride is most often used in fiber treatment. Benzoyl chloride includes
benzoyl (C6H5C=O) which is attributed to the decreased hydrophilic nature of the
treated fiber and improved interaction with the hydrophobic PS matrix. The reaction
between the cellulosic hydroxyl group of the fiber and benzoyl chloride is given
below:-
-
+
Fiber – OH + NaOH → Fiber – O Na +H2O
Benzoylation of fiber improves fiber matrix adhesion, thereby considerably
increasing the strength of composite, decreasing its water absorption and improving
its thermal stability.
The pre-treated fibers are suspended in 10% NaOH solution and agitated with
benzoyl chloride. The mixture are kept for 15 min, filtered, washed thoroughly with
water and dried between filter papers. The isolated fibers are then soaked in ethanol
for 1 h to remove the benzoyl chloride and finally are washed with water and dried in
the oven at 80° C for 24 h.
4.3.4 Silane Treatment
Silane is a chemical compound with chemical formula SiH4. Silanes are used as
coupling agents to let glass fibers adhere to a polymer matrix, stabilizing the
composite material. Silane coupling agents may reduce the number of cellulose
hydroxyl groups in the fiber–matrix interface. In the presence of moisture,
hydrolysable alkoxy group leads to the formation of silanols. The silanol then reacts
with the hydroxyl group of the fiber, forming stable covalent bonds to the cell wall
that are chemisorbed onto the fiber surface .Therefore, the hydrocarbon chains
provided by the application of silane restrain the swelling of the fiber by creating a
cross-linked network due to covalent bonding between the matrix and the fiber. The
reaction schemes are given as follows:
57
CH2CHSi (OC2H5)3
2O
H

→ CH2CHSi (OH3) +3C2H5OH
CH2CHSi (OH3) +Fiber-OH → CH2CHSi (OH)2O-Fiber + H2O
Silane coupling agents were also found to be effective in modifying natural fiber–
polymer matrix interface and increasing the interfacial strength.
4.3.5 Permanganate Treatment
Permanganate is a compound that contains permanganate group MnO4− .
Permanganate treatment leads to the formation of cellulose radical through MnO3− ion
formation. Then, highly reactive Mn3+ ions are responsible for initiating graft
copolymerization as given below:
Most permanganate treatments are conducted by using potassium permanganate
(KMnO4) solution As a result of permanganate treatment, the hydrophilic tendency of
the fibers is reduced, and hence, the water absorption of fiber-reinforced composite
decreased.
4.3.6 Peroxide Treatment
In organic chemistry, peroxide is a specific functional group or a molecule with
the functional group ROOR containing the divalent ion O−O. Organic peroxides tend
to decompose easily to free radicals of the form RO; RO then reacts with the
hydrogen group of the matrix and cellulose fibers. For example, the peroxide initiated
free radical reaction between polyethylene (P.E.) matrix and cellulose fibers is shown
by the following:
RO – OR →2RO
RO + PE − H→ ROH + PE
RO + Cellulose – H → ROH + Cellulose
58
PE + Cellulose → PE – Cellulose
As a result of peroxide treatment, the hydrophilicity of the fibers decreased and the
tensile properties increased.
4.3.7 Isocyanate Treatment
An isocyanate is a compound containing the isocyanate functional group –
N=C=O, which is highly susceptible to reaction with the hydroxyl groups of cellulose
and lignin in fibers. The reaction between fiber and isocyanate coupling agent is
shown below:
where R could be different chemical groups (such as alkyl).
4.3.8 Acrylic Acid Treatment
Treatments like silane and acrylation led to strong covalent bond formation and
thereby, the tensile strength and Young’s modulus of treated fibers were improved
marginally.
4.3.9Maleic anhydride Treatment
Maleated coupling agents are widely used to strengthen composites containing
fillers and fiber reinforcements. The difference with other chemical treatments is that
maleic anhydride is not only used to modify fiber surface but also the Polypropylene
matrix to achieve better interfacial bonding and mechanical properties in composites.
4.3.10 Sodium chlorite (NaClO2) Treatment
Sodium chlorite (NaClO2) usually is used in bleaching fibers. Tensile strength of
bleached sisal fiber–polystyrene composite was less than other chemical treated fiber
composites which may be due to the fact that delignification of the fiber lowered its
tensile strength. But it was reported that flexural strength was better for bleached fiber
composite because of lower stiffness and more flexible character of fibers after
delignification. After delignification, the polymer replaces the role of lignin in fibers
and makes composites more hydrophobic and tougher [82].
59
4.4 FABRICATION OF COMPOSITES WITH MODIFIED RICE
HUSK
AS REINFORCEMENT
For preparation of composites to conduct mechanical and erosion test the
requirement of materials has been discussed in CHAPTER-3 Art: 3.5 & 3.6. It was
found that for tensile and flexural test 15% weight fraction and for erosion test 20%
weight fraction of fiber given the best result. To enhance the mechanical and erosion
wear properties the reinforced material i.e. rice husk is modified with suitable
chemical treatments. Out of the number of chemical modification method discussed in
Art: 4.3, the two chemical modification methods i.e. acetone treatment and alkali
treatment is adopted for present research work.
4.4.1 Fiber preparation with acetone treatment:
The rice husk fibers were washed in soxhlet extractor (Figure-4.1) with acetone
for approximately 1.5-2.0 hrs. The acetone was evaporated (boiled at 630C) and
condensed back into the volume with the fibers. Used acetone was discarded before
the new batch was cleaned in the same manner. This process was repeated four times
for each batch. The color of acetone changed after each batch of treatment due to the
presence of waxes and organic materials. Hence in each batch the used acetone has to
be changed. All the fibers were washed with pressurized water at a temperature of
900C for 70 minutes before acetone treatment. The fibers were then dried at room
temperature for 24 hrs.
4.4.2 Fiber preparation with alkali treatment:
The rice husk fibers were soaked in a 5% (w/w) NaOH solution at room
temperature, maintaining a liquor ratio of 15:1 (w/w). The fibers were kept immersed
in the alkali solution for 4 hrs. as reported by Acharya et al. [83] that natural fibers
soaked with alkali with 5% concentration and for 4 hours given the best result for the
mechanical properties. The fibers were then washed several times with fresh water to
remove any NaOH sticking to the fiber surface and if required washed with dilute
acetic acid and again with water to achieve a final pH of 7. The fibers were then dried
at room temperature for 48 hrs, followed by oven drying at 80°C for 8 hrs.
60
4.5 PREPARATION OF COMPOSITE SLABS FOR TENSILE
TEST AND BEND TEST
The same procedure( i.e. as per CHAPTER-3, Art: 3.6 & 3.7) has been adopted to
prepare composite slabs for tensile test and bend test .But only difference is that
instead of plain (untreated) rice husk we are using chemically treated rice husk i.e.
acetone treated and alkali treated rice husk has taken as a reinforced material.
4.6 TENSILE TEST AND BEND TEST
The method of conduction of these tests has been discussed in CHAPTER-3, Art3.8 &3.9. The results obtained from the tests are presented in Table-4.1 & Table-4.2.
4.7 RESULTS AND DISCUSSION:
The tensile strength results for various specimens were plotted in Figure-4.2 &
Figure-4.3. From Fig.4.2 and Fig.4.3 it is observed that treatment of rice husk with
acetone and alkali increases the bonding strength with epoxy, hence the tensile
strength and flexural strength increases. It is seen that 15% weight fraction of acetone
treated rice husk reinforced epoxy composites gives maximum tensile strength and
bending strength than untreated and alkali treated.
Table-4.1 Tensile and flexural strength for acetone treated rice husk reinforced
epoxy composites.
Weight fraction of
Acetone treated RH
Tensile Strength (MPa)
Flexural strength (MPa)
0%
14.07
18.18
5%
17.18
21.01
10%
19.96
29.32
15%
20.61
33.07
20%
18.10
29.11
61
Table-4.2 Tensile and flexural strength for alkali treated rice husk reinforced
epoxy composites.
Weight fraction of
Alkali treated RH
Tensile Strength (MPa)
Flexural strength (MPa)
0%
14.07
18.18
5%
15.41
20.65
10%
18.74
22.60
15%
19.51
25.87
20%
16.70
19.29
Epoxy
5%
10%
15%
20%
Tensile Strength (MPa)
20
15
10
5
0
PRH
Acetone
Alkali
Figure-4.1 Effect of fiber modification by acetone and alkali treatment on tensile
strength.
35
Epoxy
5%
10%
15%
20%
Flexural Strength (MPa)
30
25
20
15
10
5
0
PRH
Acetone
Alkali
Figure-4.2 Effect of fiber modification by acetone and alkali treatment on
flexural strength.
62
4.8 PREPARATION OF SPECIMENS FOR SOLID PARTICLE
EROSION TEST
The same procedure (i.e. as per CHAPTER-3, Art: 3.6 & 3.11) has been adopted
to prepare composite slabs for erosion tests. But only difference is that instead of
plain (untreated) rice husk we are using chemically treated rice husk i.e. acetone
treated and alkali treated rice husk has taken as a reinforced material.
4.9 CALCULATION
After the experiments the values of weight loss erosion rate velocity exponents &
erosion efficiency have been calculated as per Chapter-3, Art- 3.11.2 and the values
are listed in the tables 4.3 to table 4.13.
4.10 X-RAY DIFFRACTION
X-ray diffraction is a useful method for evaluating the crystallographic structure
of semi-crystalline materials such as Rice-Husk fiber. A Philips X-ray diffractometer
PAN alytical, employing CuKα (λ = 1.54) radiation and a graphite monochromator
with a current of 40 mA and a voltage of 40 mV was used with a diffraction intensity
in the range of 5° to 45° (2θ-angle range).
In Figure 4.28, one peak can be observed for PRH, alkali & acetone: at 22.7° 2θ,
which indicates the presence of amorphous silica, quartz & calcite which corresponds
to carbon (Krishnarao et al., 2001) [84]. Plane Rice-Husk shows highest crystallinity
than treated rice husk (Acetone & Alkali) although important changes in the
diffractogram were not observed after treatment. Due to treatment the peak was
decreasing this shows that due to treatment some of the silica is washed out.
4.11 SCANNING ELECTRON MICROSCOPY STUDY
The morphology of the untreated and treated fiber surfaces has been studied using
scanning electron microscope (SEM) JEOL JSM-6480LV. The sample surfaces were
platinum coated to make them conductive prior to SEM observation. The eroded
surfaces of RH-epoxy composites subjected to different impingement angles at
different impact velocities are shown in Figure 4.29. The wear mechanisms in neat
epoxy are more dominated by brittle failure. The erosion damage was dominantly
reflected by formation of micro-cracks at surface which finally forms wear debris.
Rice-Husk contains silica which is a typical brittle material. During normal
63
impingement greater amount of impact energy is utilized for crack initiation and local
fracture of material. The pulverized wear debris is adhered to the matrix and helps in
reducing further wear of composite. This effect is responsible for the low erosion rate
of RH-composite as compared to neat epoxy.
4.12 RESULTS AND DISCUSSION
Fig-4.4 to Fig-4.11 shows the comparison of erosion wear rate between untreated
and treated rice husk epoxy composites. It is clear from the figure that in case of
treated rice husk epoxy composite the erosion wear rate is minimum as compared to
untreated rice husk epoxy composite. This happened because the compatibility
between rice husk particles and polymer increases due to fiber treatment. This is
possible because the treatment completely wets the surface of RH and more and more
OH groups are used for chemical bonding. From Fig-4.4 to Fig 4.11 it is observed that
if the rice husk treated with acetone then it gives better erosive wear property than
untreated and alkali treated rice husk reinforced epoxy composites.
4.13 CONCLUSION
1. Chemical treatment of RH fiber increased the fiber-matrix adhesion and in
both kind of treatments i.e. acetone treatment and alkali treatment the
mechanical properties of the composite improved.
2. Based on mechanical testing it was observed that acetone treatment of the
RH fiber gives optimum result as compared to PRH and alkali treatment and
15% acetone treated RH-epoxy composite shown the best result.
3. Fiber breakages are found to be the predominant mode of failure as
ascertained from the morphology of the treated fiber composites.
4. The incorporation of chemically treated rice husk in to epoxy reduced the
erosive wear loss significantly compared to PRH epoxy composite.
5. Erosion test of the chemically treated RH epoxy composite shown that alkali
treatment give maximum erosion resistance to the composite compared to
the acetone treatment.
6. The optimal wear resistance property was obtained at a fiber content of 20%
weight fraction with alkali treatment.
64
7. The influence of impingement angle on erosive wear of composites under
consideration exhibits semi-brittle erosive wear behavior with maximum
wear rate between 45°-60° impingement angle.
8. With increasing of the velocity of impingement, erosion rate gradually
increases.
9. In chemically treated RH-epoxy composites the erosion rate (Er) displayed the
power law behavior with particle velocity (v), Er α vn, where ‘n’ varies from
2.40 to 3.19 which further explains its semi-brittle behavior.
10. The erosion efficiency (η) values obtained experimentally also indicate that
the Plain Rice-Husk (PRH) fiber reinforced epoxy composites exhibit semibrittle erosion response (1.211%-5.142%).
11. The morphologies of eroded surface of the samples observed by SEM indicate
that, material removal is mainly due to micro-cutting and micro-ploughing.
65
Table- 4.3: Weight loss & erosion rate of 5% Acetone treated RH epoxy
composite for a period of 5 minutes at different velocities and angles.
Velocity
(m/s)
48
70
82
109
Acetone 5%
Angle
(degree)
Weight of
impingement
(gm)
Weight loss
(gm)
Erosion Rate
Er x 10-4
(gm/gm)
30
55
0.010
1.753
45
55
0.012
2.164
60
55
0.010
1.805
90
55
0.006
1.175
30
55
0.024
4.436
45
55
0.045
8.164
60
55
0.036
6.545
90
55
0.023
4.182
30
55
0.041
7.382
45
55
0.056
10.255
60
55
0.068
12.364
90
55
0.045
8.145
30
55
0.077
14.055
45
55
0.094
17.055
60
55
0.101
18.364
90
55
0.079
14.400
66
Table- 4.4: Weight loss & erosion rate of 10% Acetone treated RH epoxy
composite for a period of 5 minutes at different velocities and angles.
Velocity
(m/s)
48
70
82
109
Acetone 10%
Angle
(degree)
Weight of
impingement
(gm)
Weight loss
(gm)
Erosion Rate
Er x 10-4
(gm/gm)
30
55
0.009
1.725
45
55
0.011
2.087
60
55
0.009
1.549
90
55
0.008
1.442
30
55
0.023
4.182
45
55
0.037
6.691
60
55
0.033
6.000
90
55
0.020
3.636
30
55
0.039
7.091
45
55
0.056
10.182
60
55
0.063
11.527
90
55
0.053
9.691
30
55
0.075
13.636
45
55
0.090
16.400
60
55
0.097
17.709
90
55
0.085
15.527
67
Table- 4.5: Weight loss & erosion rate of 15% Acetone treated RH epoxy
composite for a period of 5 minutes at different velocities and angles.
Velocity
(m/s)
48
70
82
109
Acetone 15%
Angle
(degree)
Weight of
impingement
(gm)
Weight loss
(gm)
Erosion Rate
Er x 10-4
(gm/gm)
30
55
0.009
1.573
45
55
0.011
1.913
60
55
0.008
1.373
90
55
0.006
1.091
30
55
0.023
4.091
45
55
0.034
6.091
60
55
0.028
5.091
90
55
0.023
4.182
30
55
0.033
6.000
45
55
0.048
8.800
60
55
0.054
9.891
90
55
0.046
8.309
30
55
0.071
12.855
45
55
0.080
14.545
60
55
0.093
16.891
90
55
0.077
14.055
68
Table- 4.6: Weight loss & erosion rate of 20% Acetone treated RH epoxy
composite for a period of 5 minutes at different velocities and angles.
Velocity
(m/s)
48
70
82
109
Acetone 20%
Angle
(degree)
Weight of
impingement
(gm)
Weight loss
(gm)
Erosion Rate
Er x 10-4
(gm/gm)
30
55
0.006
1.053
45
55
0.008
1.475
60
55
0.007
1.218
90
55
0.007
1.209
30
55
0.015
2.727
45
55
0.028
5.145
60
55
0.023
4.145
90
55
0.016
2.896
30
55
0.028
5.000
45
55
0.041
7.527
60
55
0.049
8.836
90
55
0.037
6.782
30
55
0.062
11.345
45
55
0.067
12.255
60
55
0.086
15.564
90
55
0.073
13.327
69
Table- 4.7: Weight loss & erosion rate of 5% Alkali treated RH epoxy composite
for a period of 5 minutes at different velocities and angles.
Velocity
(m/s)
48
70
82
109
Angle
(degree)
Weight of
impingement
(gm)
30
Alkali 5%
Weight loss
(gm)
Erosion Rate
Er x 10-4
(gm/gm)
55
0.008
1.515
45
55
0.011
2.078
60
55
0.008
1.527
90
55
0.008
1.382
30
55
0.027
4.873
45
55
0.040
7.273
60
55
0.031
5.618
90
55
0.023
4.182
30
55
0.040
7.273
45
55
0.050
9.091
60
55
0.063
11.527
90
55
0.049
8.836
30
55
0.070
12.727
45
55
0.088
16.000
60
55
0.094
17.055
90
55
0.074
13.527
70
Table- 4.8: Weight loss & erosion rate of 10% Alkali treated RH epoxy
composite for a period of 5 minutes at different velocities and angles.
Velocity
(m/s)
48
70
82
109
Angle
(degree)
Weight of
impingement
(gm)
30
Alkali 10%
Weight loss
(gm)
Erosion Rate
Er x 10-4
(gm/gm)
55
0.008
1.424
45
55
0.011
1.971
60
55
0.008
1.442
90
55
0.007
1.256
30
55
0.016
2.998
45
55
0.033
6.036
60
55
0.029
5.182
90
55
0.018
3.200
30
55
0.035
6.273
45
55
0.047
8.509
60
55
0.060
10.818
90
55
0.044
7.909
30
55
0.063
11.473
45
55
0.080
14.545
60
55
0.090
16.291
90
55
0.064
11.636
71
Table- 4.9: Weight loss & erosion rate of 15% Alkali treated RH epoxy
composite for a period of 5 minutes at different velocities and angles.
Velocity
(m/s)
48
70
82
109
Angle
(degree)
Weight of
impingement
(gm)
30
Alkali 15%
Weight loss
(gm)
Erosion Rate
Er x 10-4
(gm/gm)
55
0.008
1.402
45
55
0.010
1.796
60
55
0.007
1.253
90
55
0.005
0.987
30
55
0.016
2.836
45
55
0.028
5.091
60
55
0.023
4.200
90
55
0.019
3.418
30
55
0.025
4.600
45
55
0.042
7.636
60
55
0.050
9.164
90
55
0.036
6.545
30
55
0.059
10.655
45
55
0.069
12.600
60
55
0.084
15.182
90
55
0.066
12.018
72
Table- 4.10: Weight loss & erosion rate of 20% Alkali treated RH epoxy
composite for a period of 5 minutes at different velocities and angles.
Velocity
(m/s)
48
70
82
109
Angle
(degree)
Weight of
impingement
(gm)
30
Alkali 20%
Weight loss
(gm)
Erosion Rate
Er x 10-4
(gm/gm)
55
0.005
0.905
45
55
0.007
1.335
60
55
0.006
1.164
90
55
0.006
1.104
30
55
0.013
2.331
45
55
0.023
4.255
60
55
0.019
3.473
90
55
0.015
2.718
30
55
0.023
4.164
45
55
0.035
6.436
60
55
0.044
8.036
90
55
0.033
6.000
30
55
0.051
9.273
45
55
0.060
10.964
60
55
0.078
14.236
90
55
0.061
11.073
73
Table- 4.11: Parameters characterizing the velocity dependence of
erosion rate of acetone and alkali treated RH reinforced epoxy
composite.
Fiber Type
Acetone 5%
Acetone 10%
Acetone 15%
Acetone 20%
Angle
(Degree)
k x 10-6
n
30
85
2.57
45
147
2.52
60
25
2.91
90
7
3.12
30
88
2.55
45
120
2.55
60
12
3.05
90
11
3.03
30
79
2.55
45
134
2.50
60
8
3.13
90
5
3.19
30
12
2.92
45
67
2.61
60
5
3.19
90
10
3.01
74
Alkali 5%
Alkali 10%
Alkali 15%
Alkali 20%
30
65
2.62
45
158
2.48
60
13
3.04
90
21
2.88
30
54
2.61
45
162
2.45
60
11
3.06
90
21
2.84
30
90
2.47
45
175
2.40
60
7
3.14
90
6
3.11
30
13
2.86
45
63
2.60
60
6
3.15
90
14
2.89
75
Table-4.12: Erosion efficiency (η) of acetone treated RH reinforced epoxy
composite.
Impact
Velocity
(m/s)
48
70
82
109
Acetone
5%
Acetone
10%
Acetone
15%
Acetone
20%
H=136.3
(MPa)
H=144.2
(MPa)
H=153 1
(MPa)
H=162.8
(MPa)
ρ=1148
(Kg/m3)
ρ =1161
(Kg/m3)
ρ =1133
(Kg/m3)
ρ =1129
(Kg/m3)
30
1.806
1.860
1.844
1.318
45
2.230
2.250
2.242
1.846
60
1.861
1.670
1.609
1.525
90
1.211
1.555
1.279
1.513
30
2.150
2.120
2.255
1.605
45
3.956
3.392
3.357
3.028
60
3.172
3.042
2.806
2.440
90
2.027
1.843
2.305
1.705
30
2.607
2.620
2.410
2.145
45
3.621
3.761
3.535
3.228
60
4.366
4.259
3.973
3.790
90
2.877
3.580
3.337
2.909
30
2.809
2.851
2.922
2.754
45
3.409
3.429
3.306
2.975
60
3.670
3.703
3.840
3.778
90
2.878
3.246
3.195
3.235
Impact
Angle
(Degree)
76
Table-4.13: Erosion efficiency (η) of alkali treated RH reinforced epoxy
composite.
Impact
Velocity
(m/s)
48
70
82
109
Alkali 5%
Alkali 10%
Alkali 15%
Alkali 20%
Impact
Angle
(Degree)
H=168.7
(MPa)
H=177.5
(MPa)
H=203
(MPa)
H=194.2
(MPa)
ρ=1125
(Kg/m3)
ρ =1131
(Kg/m3)
ρ =1131
(Kg/m3)
ρ =1133
(Kg/m3)
30
1.971
1.939
2.184
1.347
45
2.705
2.685
2.799
1.986
60
1.988
1.964
1.952
1.731
90
1.799
1.712
1.538
1.642
30
2.982
1.920
2.078
1.631
45
4.451
3.867
3.730
2.977
60
3.439
3.319
3.077
2.430
90
2.560
2.050
2.504
1.902
30
3.244
2.928
2.456
2.123
45
4.055
3.972
4.077
3.281
60
5.142
5.050
4.892
4.097
90
3.941
3.692
3.494
3.059
30
3.213
3.031
3.219
2.675
45
4.039
3.843
3.807
3.163
60
4.305
4.304
4.587
4.108
90
3.415
3.074
3.631
3.195
77
Figure 4.3: Soxhlet Extractor
78
2.6
48 m/s, 5%
Erosion Rate x 10-4
2.4
2.2
2.0
1.8
Neat Epoxy
1.6
PRH 5%
1.4
Acetone 5%
1.2
Alkali 5%
1.0
0.8
15
30
45
60
75
90
Impingement Angle (degree)
Figure-4.4: Comparison of erosion rate versus impingement angle of neat epoxy
& 5% wt. fraction of PRH and treated RH epoxy composite at the velocity of 48
m/s.
2.6
48 m/s, 10%
Erosion Rate x 10-4
2.4
2.2
2.0
1.8
Neat Epoxy
1.6
PRH 10%
1.4
Acetone 10%
1.2
Alkali 10%
1.0
0.8
15
30
45
60
75
90
Impingement Angle (degree)
Figure-4.5: Comparison of erosion rate versus impingement angle of neat epoxy
& 10% wt. fraction of PRH and treated RH epoxy composite at the velocity of 48
m/s.
79
2.6
48 m/s, 15%
Erosion Rate x 10-4
2.4
2.2
2.0
1.8
Neat Epoxy
1.6
PRH 15%
1.4
Acetone 15%
1.2
Alkali 15%
1.0
0.8
15
30
45
60
75
90
Impingement Angle (degree)
Figure-4.6: Comparison of erosion rate versus impingement angle of neat epoxy
& 15% wt. fraction of PRH and treated RH epoxy composite at the velocity of 48
m/s.
2.6
48 m/s, 20%
Erosion Rate x 10-4
2.4
2.2
2.0
1.8
Neat Epoxy
1.6
PRH 20%
1.4
Acetone 20%
1.2
Alkali 20%
1.0
0.8
15
30
45
60
75
90
Impingement Angle (degree)
Figure-4.7: Comparison of erosion rate versus impingement angle of neat epoxy
& 20% wt. fraction of PRH and treated RH epoxy composite at the velocity of 48
m/s.
80
10.0
70 m/s, 5%
Erosion Rate x 10-4
9.0
8.0
7.0
6.0
Neat Epoxy
5.0
PRH 5%
4.0
Acetone 5%
3.0
Alkali 5%
2.0
1.0
15
30
45
60
75
90
Impingement Angle (degree)
Figure-4.8: Comparison of erosion rate versus impingement angle of neat epoxy
& 5% wt. fraction of PRH and treated RH epoxy composite at the velocity of 70
m/s.
10.0
70 m/s, 10%
Erosion Rate x 10-4
9.0
8.0
7.0
6.0
Neat Epoxy
5.0
PRH 10%
4.0
Acetone 10%
3.0
Alkali 10%
2.0
1.0
15
30
45
60
75
90
Impingement Angle (degree)
Figure-4.9: Comparison of erosion rate versus impingement angle of neat epoxy
& 10% wt. fraction of PRH and treated RH epoxy composite at the velocity of 70
m/s.
81
10.0
70 m/s, 15%
Erosion Rate x 10-4
9.0
8.0
7.0
6.0
Neat Epoxy
5.0
PRH 15%
4.0
Acetone 15%
3.0
Alkali 15%
2.0
1.0
15
30
45
60
75
90
Impingement Angle (degree)
Figure-4.10: Comparison of erosion rate versus impingement angle of neat epoxy
& 15% wt. fraction of PRH and treated RH epoxy composite at the velocity of 70
m/s.
10.0
70 m/s, 20%
Erosion Rate x 10-4
9.0
8.0
7.0
6.0
Neat Epoxy
5.0
PRH 20%
4.0
Acetone 20%
3.0
Alkali 20%
2.0
1.0
15
30
45
60
75
90
Impingement Angle (degree)
Figure-4.11: Comparison of erosion rate versus impingement angle of neat epoxy
& 20% wt. fraction of PRH and treated RH epoxy composite at the velocity of 70
m/s.
82
15.0
82 m/s, 5%
Erosion Rate x 10-4
13.0
11.0
9.0
Neat Epoxy
7.0
PRH 5%
Acetone 5%
5.0
Alkali 5%
3.0
1.0
15
30
45
60
75
90
Impingement Angle (degree)
Figure-4.12: Comparison of erosion rate versus impingement angle of neat epoxy
& 5% wt. fraction of PRH and treated RH epoxy composite at the velocity of 82
m/s.
15.0
82 m/s, 10%
Erosion Rate x 10-4
13.0
11.0
9.0
Neat Epoxy
7.0
PRH 10%
Acetone 10%
5.0
Alkali 10%
3.0
1.0
15
30
45
60
75
90
Impingement Angle (degree)
Figure-4.13: Comparison of erosion rate versus impingement angle of neat epoxy
& 10% wt. fraction of PRH and treated RH epoxy composite at the velocity of 82
m/s.
83
15.0
82 m/s, 15%
Erosion Rate x 10-4
13.0
11.0
9.0
Neat Epoxy
7.0
PRH 15%
Acetone 15%
5.0
Alkali 15%
3.0
1.0
15
30
45
60
75
90
Impingement Angle (degree)
Figure-4.14: Comparison of erosion rate versus impingement angle of neat epoxy
& 15% wt. fraction of PRH and treated RH epoxy composite at the velocity of 82
m/s.
15.0
82 m/s, 20%
Erosion Rate x 10-4
13.0
11.0
9.0
Neat Epoxy
7.0
PRH 20%
Acetone 20%
5.0
Alkali 20%
3.0
1.0
15
30
45
60
75
90
Impingement Angle (degree)
Figure-4.15: Comparison of erosion rate versus impingement angle of neat epoxy
& 20% wt. fraction of PRH and treated RH epoxy composite at the velocity of 82
m/s.
84
26.0
109 m/s, 5%
Erosion Rate x 10-4
21.0
16.0
Neat Epoxy
PRH 5%
11.0
Acetone 5%
Alkali 5%
6.0
1.0
15
30
45
60
75
90
Impingement Angle (degree)
Figure-4.16: Comparison of erosion rate versus impingement angle of neat epoxy
& 5% wt. fraction of PRH and treated RH epoxy composite at the velocity of 109
m/s.
26.0
109 m/s, 10%
Erosion Rate x 10-4
21.0
16.0
Neat Epoxy
PRH 10%
11.0
Acetone 10%
Alkali 10%
6.0
1.0
15
30
45
60
75
90
Impingement Angle (degree)
Figure-4.17: Comparison of erosion rate versus impingement angle of neat epoxy
& 10% wt. fraction of PRH and treated RH epoxy composite at the velocity of
109 m/s.
85
26.0
109 m/s, 15%
Erosion Rate x 10-4
21.0
16.0
Neat Epoxy
PRH 15%
11.0
Acetone 15%
Alkali 15%
6.0
1.0
15
30
45
60
75
90
Impingement Angle (degree)
Figure-4.18: Comparison of erosion rate versus impingement angle of neat epoxy
& 15% wt. fraction of PRH and treated RH epoxy composite at the velocity of
109 m/s.
26.0
109 m/s, 20%
Erosion Rate x 10-4
21.0
16.0
Neat Epoxy
PRH 20%
11.0
Acetone 20%
Alkali 20%
6.0
1.0
15
30
45
60
75
90
Impingement Angle (degree)
Figure-4.19: Comparison of erosion rate versus impingement angle of neat epoxy
& 20% wt. fraction of PRH and treated RH epoxy composite at the velocity of
109 m/s.
86
Acetone, 30°
16
Erosion Rate x 10-4
14
12
Acetone 5%
10
Acetone 10%
Acetone 15%
8
Acetone 20%
6
y = 8.51E-05x2.57
Power (Acetone 5%)
4
y = 8.81E-05x2.55
Power (Acetone 10%)
y = 7.94E-05x2.55
Power (Acetone 15%)
2
1.23E-05x2.92
Power (Acetone 20%)
y=
0
45
65
85
105
Velocity (m/s)
Figure-4.20: Variation of steady-state erosion rate of acetone treated RH-epoxy
composites as a function of impact velocity for 30° impact angle.
Acetone, 45°
25
20
Erosion Rate x 10-4
Acetone 5%
Acetone 10%
15
Acetone 15%
Acetone 20%
10
5
y=
1.47E-04x2.52
Power (Acetone 5%)
y=
1.20E-04x2.55
Power (Acetone 10%)
y=
1.34E-04x2.50
Power (Acetone 15%)
y = 6.79E-05x2.61
Power (Acetone 20%)
0
45
65
85
105
Velocity (m/s)
Figure-4.21: Variation of steady-state erosion rate of acetone treated RH-epoxy
composites as a function of impact velocity for 45° impact angle.
87
Acetone, 60°
25
20
Erosion Rate x 10-4
Acetone 5%
Acetone 10%
15
Acetone 15%
Acetone 20%
10
5
y = 2.59E-05x2.91
Power (Acetone 5%)
y = 1.29E-05x3.05
Power (Acetone 10%)
y = 8.11E-06x3.13
Power (Acetone 15%)
y = 5.57E-06x3.19
Power (Acetone 20%)
0
45
65
85
105
Velocity (m/s)
Figure-4.22: Variation of steady-state erosion rate of acetone treated RH-epoxy
composites as a function of impact velocity for 60° impact angle.
Acetone, 90°
18
16
Erosion Rate x 10-4
14
Acetone 5%
12
Acetone 10%
10
Acetone 15%
8
Acetone 20%
6
4
y = 7.06E-06x3.12
Power (Acetone 5%)
y = 1.16E-05x3.03
Power (Acetone 10%)
5.12E-06x3.19
Power (Acetone 15%)
y = 1.00E-05x3.01
Power (Acetone 20%)
y=
2
0
45
65
85
105
Velocity (m/s)
Figure-4.23: Variation of steady-state erosion rate of acetone treated RH-epoxy
composites as a function of impact velocity for 90° impact angle.
88
Alkali, 30°
16
Erosion Rate x 10-4
14
12
Alkali 5%
10
Alkali 10%
Alkali 15%
8
Alkali 20%
6
y = 6.54E-05x2.62
Power (Alkali 5%)
4
y = 5.44E-05x2.61
Power (Alkali 10%)
Power (Alkali 15%)
2
y = 9.03E-05x2.47
y = 1.36E-05x2.86
Power (Alkali 20%)
0
45
65
85
105
Velocity (m/s)
Figure-4.24: Variation of steady-state erosion rate of alkali treated RH-epoxy
composites as a function of impact velocity for 30° impact angle.
Alkali, 45°
20
18
Erosion Rate x 10-4
16
Alkali 5%
14
Alkali 10%
12
Alkali 15%
10
Alkali 20%
8
y = 1.58E-04x2.48
Power (Alkali 5%)
6
y = 1.62E-04x2.45
Power (Alkali 10%)
4
y = 1.75E-04x2.40
Power (Alkali 15%)
2
y = 6.30E-05x2.60
Power (Alkali 20%)
0
45
65
85
105
Velocity (m/s)
Figure-4.25: Variation of steady-state erosion rate of alkali treated RH-epoxy
composites as a function of impact velocity for 45° impact angle.
89
Alkali, 60°
25
20
Erosion Rate x 10-4
Alkali 5%
Alkali 10%
15
Alkali 15%
Alkali 20%
10
y = 1.32E-05x3.04
Power (Alkali 5%)
y = 1.17E-05x3.06
Power (Alkali 10%)
y = 7.10E-06x3.14
Power (Alkali 15%)
y = 6.01E-06x3.15
Power (Alkali 20%)
5
0
45
65
85
105
Velocity (m/s)
Figure-4.26: Variation of steady-state erosion rate of alkali treated RH-epoxy
composites as a function of impact velocity for 60° impact angle.
Alkali, 90°
18
16
Erosion Rate x 10-4
14
Alkali 5%
12
Alkali 10%
10
Alkali 15%
8
Alkali 20%
6
4
y = 2.13E-05x2.88
Power (Alkali 5%)
y = 2.14E-05x2.84
Power (Alkali 10%)
6.24E-06x3.11
Power (Alkali 15%)
y = 1.48E-05x2.89
Power (Alkali 20%)
y=
2
0
45
65
85
105
Velocity (m/s)
Figure-4.27: Variation of steady-state erosion rate of alkali treated RH-epoxy
composites as a function of impact velocity for 45° impact angle.
90
Figure- 4.28: XRD Pattern of untreated (PRH) and treated (Acetone & Alkali)
Rice-Husk.
91
(a)
(b)
(c)
(d)
(e)
(f)
Figure- 4.29: SEM micrographs of eroded surface of (a) (b) PRH 5% (c) (d) 10%
Acetone treated (e) (f) 20% Alkali treated
92
Chapter-5
5.1 CONCLUSION
The following conclusions are drawn from this study.
1. The Rice-Husk which is a agricultural waste product of the rice mill and
cannot be decomposed easily can be successfully utilized to produce natural
fiber polymer composite by suitably bonding with epoxy resin.
2. The addition of Rice-Husk fiber into neat epoxy significantly improved the
mechanical and erosion behavior of the material.
3. 15% weight fraction RH fiber given the best result for tensile and bend test
whereas for erosion wear test 20% weight fraction of the fiber given the best
result for the composite material.
4. The RH fibers contain the silica which contributes in improving the hardness
of the composite material.
5. The surface modification of fiber by chemical treatment improves the fiber
matrix adhesion which further enhances the mechanical and erosive wear
properties of the composite.
6. The acetone treatment provides the highest improvement in strength in
comparison to alkali treatment, whereas alkali treatment given the best result
for the erosion test in comparison to acetone treatment.
7. Erosion test shown that Rice-Husk epoxy composite exhibits semi brittle
behavior which is conformed from the experimental result and erosion
efficiency which is found to be between 1% to 6% further explains the same
behavior.
93
5.2 RECOMMENDATIONS AND FUTURE SCOPE FOR
RESEARCH WORK
1. In the present investigation a hand-lay-up technique was used to fabricate the
composite. However there existing other manufacturing process for polymer
matrix composite. They could be tried and analyzed, so that a final conclusion
can be drawn there from. However the results provided in this thesis can act as
a base for the utilization of this fiber.
2. From this work it is found that chemical modification of the fiber with acetone
and benzoyl chloride significantly improves the mechanical performance of
the composite. Other chemical modification methods such as silane treatment,
alkali treatment, acrylation treatment isocynates treatment, Permanganate
treatment, Maleated coupling agents could be tried and a final conclusion can
be drawn thereafter.
3. The erodent sand particle size used for erosion test was between 300 to 600
µm whereas the same test can be conducted with different erodent particle
size.
94
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