CHAPTER 1
1:0 INTRODUCTION
In recent years, the natural fibres have attracted substantial importance as potential structural
material. The attractive plus point of natural fibre is in terms of industrial usage which has made
its availability more demanding. Keeping this in view the present work has been undertaken to
develop a polymer matrix composite (epoxy resin) using bagasse fibre as reinforcement and to
study its mechanical properties and performance. The composites are prepared with different
volume fraction of bagasse fibre.
Kenya is a country which largely depends on agriculture. Farm products constitute the separate
joints and bones of the backbone of the country’s economy out of which natural fibre has been a
waste product which remains largely untapped. In recent years the natural fibre epoxy
composites has attracted substantial importance as a potential structural material.
The mechanical properties of several types of epoxy systems are designed based on the
chemical structure, network structure and morphology aiming at cryogenic applications such as
cryogenic wind tunnels, cryogenic transport vessels, support structures in space shuttles and
rockets. In these applications they are often under cyclic loading. The attractive features of
natural fibres like jute, sisal, coir and banana have been their low cost, light weights, high
specific modulus, renew ability and biodegradability.
Natural fibres are lingo-cellulosic in nature. These composites are gaining importance due to
their non-carcinogenic and bio-degradable nature. The natural fibre composites can be very cost
effective material especially for building and construction industry. However in many instances
residues from traditional crops such sugarcane bagasse or from the usual processing operations
of timber industries do not meet the requisites of being long fibres.
Bagasse contains about 40% cellulose, 30% hemi-cellulose, and 15% lignin. The present use of
bagasse is mainly as a fuel in the sugar cane mill furnaces, for example in Mumias Sugar
Company based in Kenya, Western province. It is felt that the value of this agricultural residue
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can be upgraded by bonding with resin to produce composites suitable for building materials.
Keeping this in view the present work has been undertaken to develop a polymer matrix
composite (epoxy resin) using bagasse fibre as reinforcement with volume fractions 10, 20, 30 &
40% and to study its mechanical properties. In the next part of this project the main emphasis
was laid on the experimental work relating to the mechanical behaviour of this composite.
Kenya is endowed with an abundant availability of natural fibres such as Jute, coir, sisal,
pineapple, ramie, bamboo, banana etc. We majorly focus on the development of natural fibres
composites primarily to explore value-added application avenues. Such natural fibre composites
are well suited as wood substitutes in the housing and construction sector. The development of
natural fibre composites in Kenya should be adapted on basis of two pronged strategy of
preventing depletion of forest resources as well as ensuring good economic returns for the
cultivation of natural fibres.
The developments in composite material after meeting the challenges of aerospace sector have
cascaded down for catering to domestic and industrial applications. Composites, the wonder
material with light-weight; high strength-to-weight ratio and stiffness properties have come a
long way in replacing the conventional materials like metals, wood etc. The material scientists all
over the world focused their attention on natural composites reinforced with Jute, Sisal, Coir,
Pineapple etc, the primarily reason being to cut down the cost of raw materials.
Usually the fibre reinforcement is done to obtain high strength and high modulus. Hence it is
necessary for the fibres to possess higher modulus than the matrix material. So the load is
transferred to the fibre from the matrix more effectively. Fibre reinforced composites are
popularly being used in many industrial applications because of their high specific strength &
stiffness. Due to their excellent structural performance these composites are gaining potential
also in tri-biological applications.
The physical properties of natural fibres are mainly determined by the chemical & physical
composition, such as structure of fibres’ cellulose content, angle of fibrils, cross section and by
the degree of polymerization. Only a few characteristics values but especially the specific
mechanical properties can reach the compensable values of traditional fibres. The application of
natural fibres as reinforcing materials in composite materials require as just for glass fibre
reinforced composites, a strong adhesion between the fibre and the matrix regardless of whether
a traditional polymer(thermoplastic or thermosetting) matrix, a biodegradable polymer matrix or
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cement is used. The mechanical and other physical properties of the composites are generally
dependent on the fibre content, which also determines the possible amount of coupling agents in
the composite.
An important property of natural fibres to be used as reinforcements is their availability in large
quantities. For several more technical oriented applications, the fibres have to be specially
prepared or modified regarding, homogeneity of the fibre’s properties, degrees of
elementarization and degumming, degree of polymerization and crystallization, good adhesion
between fibre and matrix, moisture repellent properties and flame retardant properties.
Nowadays natural fibres are very fast replacing the traditional manmade fibres as
reinforcements they have several advantages over manmade fibres, which include; plant fibres
are renewable and their availability is more or less unlimited, when natural fibre composite were
subjected to at the end of their life cycle, to a combustion process or landfill the amount of CO2
released of the fibres is neutral with respect to their assimilated amount during their growth. The
abrasive nature is lower which leads to advantages regarding technical material recycling, natural
fibre reinforced plastics by using biodegradable polymers as matrix are the most environment
friendly materials.
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1.1 OBJECTIVE
The main objective of this research was to study and evaluate the mechanical and physical
properties of sugarcane bagasse as reinforcing fibres in epoxy resin matrices. The effects of
sugarcane bagasse fibre reinforcement on epoxy resin matrix was investigated with respect to the
fibre content and their orientations on the following composite strength properties;

Tensile Strength

Tensile Modulus of Elasticity

Flexural Strength

Flexural Modulus of Elasticity
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CHAPTER 2
2.0 WHAT IS A COMPOSITE?
The most widely used meanings are the ones which have been stated by;

Jartiz defines it as ”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 in
composition and characteristics and sometimes in form”. The weakness of this definition
resided in the fact that it allows one to classify among the composites any mixture of
materials without indicating either its specificity or the laws which should given it which
distinguishes it from other very banal, meaningless mixtures.

Beghezan defines it 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 short comings”, in order to obtain improved materials.

Kelly 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 to resistance to heat or some other desirable
quality, it is better than either of the components alone or radically different from either
of them.

Van Suchetclan 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.
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2.1 WHY STUDY COMPOSITES?
Over the past years composite materials, plastics and ceramics have been the dominant
emerging materials. The volume and number of applications of composite materials have grown
steadily, penetrating and conquering new markets relentlessly. Modern composite materials
constitute a significant proportion of the engineered materials market ranging from everyday
products to sophisticated applications. While composites have already proven their worth as
weight-saving materials, the current challenge is to make them cost effective.
The efforts to produce economically attractive composite components have resulted in several
innovative manufacturing techniques currently being used in the composites industry. It is
obvious, especially for composites, that the improvement in manufacturing technology alone is
not enough to overcome the cost hurdle. It is essential that there be an integrated effort in design,
material, process, tooling, quality assurance, manufacturing, and even program management for
composites to become competitive with metals.
2.2 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.
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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 crosssanctioned 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.
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.
2.3 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’) which is the binder.

A reinforcement of some kind, added primarily to increase the strength and stiffness of
the matrix.
2.4 CLASSIFICATION
Composite materials can be classified into many categories depending on the type of matrix
material, reinforcing material type etc.
According to the type of matrix material they can be classified as follows:

Metal matrix type composites: MMC are composed of a metallic matrix (Al, Mg, Fe, Co,
Cu)

Ceramic matrix composites: CMC is a material consisting of a ceramic combined with a
ceramic dispersed phase.

Polymer matrix material: PMC are composed of a matrix from thermosetting (unsaturated
polyester, epoxy) or thermoplastic (nylon, polystyrene) and embedded glass carbon, steel
or Kerler fibres (dispersed phase).
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Some of the major advantages and limitations of resin matrices are shown in Table below:
ADVANTAGES
Low densities
Good corrosion resistance
Low thermal conductivities
Low electrical conductivities
Translucence
Aesthetic Color effects
DISADVANTAGES
Low transverse strength
Low operational temperature limits
Table1. Advantages and disadvantages of polymer matrix.
Generally, the 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 which should cluster with that of the reinforcement. It must be easy to use in the
fabrication process selected and also stand up to the service conditions.
According to the type of reinforcing material type they can be classified into the following
categories:

Particle composites Particle reinforced composites consist of a matrix reinforced by a
dispersed phase in the form of particles. It can be either of random orientation or
preferred orientation.
FIG.1 PARTICULATE FIBRE COMPOSITE
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
Fibrous composites-Short fiber: they consist of a matrix reinforced by a dispersed phase
in the form of discontinuous fibers either of random or preferred orientations.
Fig 2:(a) SHORT FIBRE COMPOSITE

Long fiber composites - they consist of a matrix reinforced by a dispersed phase in the
form of continuous fibers. They can be either unidirectional or bidirectional.
(b) LONG FIBRE COMPOSITE

Laminate composites-when a fiber reinforced composite consists of several layers with
different fiber orientations, it is called multilayer composite.
We also have;
FIG. 3(a) FLAKE COMPOSITE
(b) FILLER COMPOSITES
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The two major classes are;
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.
2.4.2 Fibrous composites
A fibre is characterized by its length being much greater compared to its cross-sectional
dimensions. The dimensions of the reinforcement determine its capability of contributing its
properties to the composite. Fibres 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 other wise lead to failure, particularly with brittle
Matrices Man-made filaments or fibres of non-polymeric materials exhibit much higher strength
along their length since large flaws, which may be present in the bulk material, are minimized
because of the small cross-sectional dimensions of the fibre. In the case of polymeric materials,
orientation of the molecular structure is responsible for high strength and stiffness.
Fibres, 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 fibres together, transfer loads to the fibres, and protect them against
environmental attack and damage due to handling.
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CHAPTER 3.0
LITERATURE REVIEW
3.1 MATRIX
Many materials when they are in a fibrous form exhibit very good strength property but to
achieve these properties the fibres should be bonded by a suitable matrix. The matrix isolates the
fibres from one another in order to prevent abrasion and formation of new surface flaws and acts
as a bridge to hold the fibres in place. A good matrix should possess ability to deform easily
under applied load, transfer the load onto the fibres and evenly distributive stress concentration.
3.2 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 fibers 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. Different ways for assembling fibres into sheets and the variety of fibre
orientations make it possible to achieve different characteristics. Agro-based fibres are classified
according to what part of the plant they come from. Five different fibre classifications are;

Bust or stem fibres , which are fibrous bundles in the inner bark of the plant stem running
the length of the stem.

Leaf fibres, which run the length of the leaves.
Seed-hair fibres.

Core, pith or stick fibres, which form the low density, spongy inner part of the stem of
certain plants. All other plant fibres not included above.
Examples of bust or stem fibres include; jute, flax, hemp, kenaf, ramie, roselle and urena. Leaf
fibres include; bananas, sisal, henequen, abaca, pineapple, cantala , caroa, mauritius and
phormium.
Seed-hair fibres include; coir, cotton, kapok, and milk weed floss. Core fibres represent the
centre or pith fibres of such plants as kenaf and jute and can represent over 85% of the dry
weight of these plants. The remaining fibres include; roots, leaf segments, flower heads and seed
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3.3 MATERIALS USED
3.3.1 BAGASSE FIBER-REINFORCEMENT
Figure 4: Bagasse fibre
Sugarcane bagasse is a residue widely generated in high proportions in the agro-industry. It is a
fibrous residue of cane stalks left over after the crushing and extraction of juice from the sugar
cane. Bagasse is generally gray-yellow to pale green in colour. It is bulky and quite non uniform
in particle size. The sugar cane residue bagasse is an under utilized, renewable agricultural
material that consist of two distinct cellular constituents. The first is a thick walled, relatively
long, fibrous fraction derived from the rind and fibro-vascular bundles dispersed throughout the
interior of the stalk. The second is a pith fraction derived from the thin walled cells of the ground
tissue. The main chemical constituents of bagasse are:
 Cellulose and hemicelluloses; They are present in the form of hollow cellulose in bagasse
which contributes to about 70 % of the total chemical constituents present in bagasse.
 Lignin; It acts as a binder for the cellulose fibres and also behaves as an energy storage
system.
Bagasse consists of water, fibre and small quantities of solids in solution in the following
proportions. Water 46-57 %( mean50%), Fibre 43%-53 %( mean 47%), Solids in solution (sugar)
2%-6 % (mean 3%).
It is a composition within certain limits as variable and depends in the varieties, their maturity,
the harvest technique and efficiency of milling.
By definition the fibre of the bagasse is the component which is insoluble in water. It consists of
mainly cellulose pentosens and lignin.
Cellulose is a polysaccharide having the general formula (C6H10O6)n and the main constituent of
vegetable tissue. According to its degree of solubility in caustic soda, cellulose is classified as;
 ∞-Cellulose, portion insoluble in a 17.5%solution caustic soda at 20 oC
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
β- Cellulose in a 17.5 % solution of caustic soda but easily precipitated when the solution
is acidified.

α- Cellulose, like in 2 and not precipitated by acids but by alcohol.
The soluble cellulose, alpha and beta are called hemi-cellulose. Pentosans are a form of hemicellulose which on hydrolysis yield xylose and arabinose and heating with steam is important
industrially and can be expressed as follows;
C5H8O4 →
(Pentosan)
C5H10 → C5H9O2
(pentose)
(furfural)
The third costituent of the fibre is lignin, a substance with a high molecular weight and which
structure and size have not yet been satisfactorily established being richer in carbon, cellulose,
and lignin is used essentially for combustion.
On average bagasse composition can be estimated as follows;
Composition
Raw bagasse
Fibre
pith
Alpha (α)
Pentosans
Lignin
Ash
35.0%
27.0%
21.0%
1.5%
0.5%
22.0%
26.0%
49.0%
35.0%
29.0%
21.0%
0.2%
Table 2. Composition of bagasse
Physically bagasse fibre is considered to be made up of 60% true fibre and 40% pith.The true
fibre has an average length of 1.5mm and length to diameter ratio of 70.The pith has a mean
length of 0.3 mm and length to diameter ratio of 5.
Physical composition varies within narrow limits. As far as calorific value is concerned,
moisture as is the most important factor. A bagasse at 45% moistire is a result of exellent milling
whereas, 52% moisture is poor milling efficiency with low heating value. In general, bagasse
moisture of 48% is the reality today with standard sugar mills.
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Apart from water, bagasse contains;

Fibre- The components of which are carbon, hydrogen and oxygen.
Some sucrose (1-2%)

Mineral salts

Extraneous matter (soil, rocks etc)
Mechanical harvesting does bring soil and crushed stones with the cane; these decreases calorific
value of bagasse. Bagasse coming from mills at 48% moisture does not keep well.
It is subject to fermentation and chemical reaction that can bring the outbreak of slow internal
combustion upto complete combustion. When bagasse is stored in a room, one must prevent the
entry of droughts if internal combustion has already started, otherwise, spontaneous combustion
will occur. Bagasse dried to moisture content of less than 30% can be stored upto one year. A
process developed in Brazil called bagatex 20 using an enzyme to dry the bagasse to less than
20% moisture content is worth to note. Below are physical properties of bagasse.
TYPE OF FIBRE
CELLLULOSE
(%)
FIBRE
DIMENSION
(mm)
LIGNIN
MEAN (%)
LENGTH
MEAN WIDTH
(mm)
Cotton
Seed flax
Hemp
Abaca
Sisal
Kenaf
Jute
Coniferouswood
Esparto
Papyrus
Sugarcane bagasse
Cereal straw
Rice straw
Deciduous
Coir
85-90
43-47
57-77
56-63
47-62
44-57
45-63
40-45
33-38
38-44
32-37
31-45
28-38
38-49
35-62
0.7-1.6
21-23
9-13
7-9
7-9
15-19
21-26
26-34
17-19
16-19
18-26
16-19
12-16
23-30
30-45
25
30
20
6.0
3.3
2.6
2.5
4.1
1.9
1.8
1.7
1.5
1.4
1.2
0.7
0.02
0.02
0.022
0.024
0.02
0
0.02
0.025
0.013
0.012
0.02
0.023
0.008
0.03
0.02
Table3:Physical properties of bagasse fibre
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Below are the mechanical properties of some natural fibre;
FIBRE TYPE
sugarcane sisal
jute
Water
reed
N/A
coconut Bamboo
FIBRE
LENGTH
(MM)
FIBRE
DIAMETER
(MM)
RELATIVE
DENSITY
MODULUS OF
ELASTICITY
GPA
ULTIMATE
TENSILE
STRENGTH
MPA
ELONGATION
AT BREAK %
WATER
ABSORPTION
%
N/A
N/A
175300
50-100
N/A
0.2-0.4
N/A
0.10.2
N/A
0.1-0.2
0.05-0.4
1.12-1.15
N/A
N/A
1.121.15
19-26
1.5
13-26
1.0210.5
26-32
15-19
180-290
275570
250350
70
120200
350-500
N/A
3-5
1.2
10-25
N/A
70-75
60-70
1.51.9
N/A
N/A
130180
N/A
5
33-40
Table4: Mechanical properties of commonly used natural fibres
N.B N/A-Properties not readily available or not applicable
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3.3 .2 EPOXY RESIN
Plastics can be broadly classified into two classes namely thermoplastics and thermosets.
Thermoplastics are anisotropic, high molecular weight strong solids and do not crosslink. They
soften on heating but upon cooling regains their original mechanical properties
Typical examples in clued nylon 6-6, polypropylene and polycarbonates among others. They yield
and undergo large deformation before final fracture. Their mechanical properties are however
depended on the temperature and applied strain rate so they creep under constant load. This means
that in a composite system there will be a redistribution of the load between the resin and fibres
during deformation.
Thermosetting resins on the other hand are isotropic and brittle. They harden by a process of
chemical cross-linking and do not melt on heating. Examples in this category include polyester,
epoxy, phenolics, silicons and polyamides. Epoxy resins may be defined as resins in which chain in
extension and cross-linking occurs through the reactions of epoxide group.
This epoxy has outstanding properties which are utilized as the matrix material.

Excellent adhesion to different materials.

High resistance to chemical and atmospheric attack.

High dimensional stability.

Free stresses.

Excellent mechanical and electrical properties.

Odorless, tasteless and completely nontoxic.

Negligible shrinkage.
The majority of epoxy resins used in composites are manufactured by the reaction of epichlorhydrin
with materials such as bisphenol A or aromatic amines as it has been noted below.
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Liquid Epoxy Resin
This is a reaction product of epichlorohydrin and bisphenol A. One of the epoxies available in the
markets from Dow Chemical Company is;
D.E.R. 330 Epoxy Resin

This is a liquid epoxy resin processed to provide low viscosity without the use of
diluents. The physical strength, toughness, excellent adhesion, chemical resistance
and low shrinkage properties have established liquid epoxy resins as major raw
materials for high quality solvent-free coatings, linings, industrial flooring, grouts and
concrete reinforcements. They have also found application in the fields of tooling,
encapsulation, adhesives, filament winding and laminates.

D.E.R. 330 Resin can also serve as a basis for advanced polymers for a variety of
solvent-borne, water-borne and UV-curable resins. A wide variety of curing agents is
available to cure this liquid epoxy resin at ambient conditions. The most frequently
used are aliphatic polyamines, polyamides, and modified versions of these. If
anhydride or catalytic curing agents are employed, elevated temperatures cures are
necessary and long post-cures are required to develop full end properties.
Epoxy resins contain a reactive oxirane structure
This is commonly referred to as“epoxy” functionality.
Liquid epoxy resins are converted through these reactive epoxy sites into tough, insoluble, and
infusible solids.
The simplest possible epoxy resin derived from the reaction of bisphenol A and epichlorohydrin is
(2,2-bis[4-(2'3' epoxy propoxy) phenyl] propane), commonly called the diglycidyl ether of bisphenol
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The higher molecular weight homologs are represented by the following theoretical structure:
Generic Bisphenol A Based Epoxy Resin Chemical Structure
With increasing molecular weight, another reactive site — the OH group is introduced. This group
can react at higher temperatures with anhydrides, organic acids, amino resins, and phenolic resins, or
with epoxide groups (when catalyzed) to give additional cross-linking.
In high melting point solid resins, “n” may be as high as 18.
3.4 MODIFICATION ON EPOXIES
Some additions are added to the epoxy resin for various reasons though the major reasons are to
reduce cost and to improve workability. They are grouped in three forms namely; reactive diluents,
modifiers and fillers. Each form has specific functions as explained below.
3.4.1 REACTIVE DILUENTS
A reactive diluent is used primarily to reduce viscosity. Adding reactive diluents also permits higher
filler loading and gives better wetting and impregnation. Preferably, the diluents should react with the
curing agent at approximately the same rate as the resin, contribute substantial viscosity reduction at
low concentrations, and be nonreactive with the resin under normal storage conditions.
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Reactive diluents in common use are:
Butyl Glycidyl Ether (BGE) (Molecular weight - 130)
C12-C14 Aliphatic Glycidyl Ether (Molecular weight -242-270)
Cresyl Glycidyl Ether (CGE) (Molecular weight - 165)
2
- Ethylhexyl Glycidyl Ether (Molecular weight-186
3.4.2 MODIFIERS
Epoxy resins may be modified for several reasons:

To enhance physical properties, such as impact strength and adhesion.

To alter viscosity,

To improve life, lower exotherm, or reduce shrinkage.
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
To lower the cost of the formulation.
Butyl glycidyl ether which is a diluent produces maximum viscosity reduction. However, excessive
exposure to these products may present serious health hazards, hence a need for adherence to safety
precautions. The higher molecular- weight reactive diluents (like the C12-C14 aliphatic ethers), are
safer to work with, but not quite as efficient as the former. Figure 1 shows the viscosity-diluents
concentration relationship for representative epoxy resins
Effect of Diluents on Epoxy Resins
Figure: 5
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Resin Modifiers
Resin modifiers are used to improve:

Mechanical and thermal shock resistance,

Increase elongation, and obtain higher impact strength and flexibility.
Usually there is some sacrifice of physical strength, electrical properties, chemical or solvent
resistance, or elevated temperature performance.
We have two types of modifiers namely; reactive modifiers and Non-reactive modifiers.
Reactive epoxide-type modifiers
The reactive modifiers from Dow Chemical Comany include;

D.E.R. 732 Aliphatic diepoxides

D.E.R. 736 flexible epoxy resins
Mono-functional epoxide compounds (such as C12 - C14 Glycidyl Ether.
Such compounds can be used at ratios up to 1:1 to obtain a flexible cured composition. They have the
added advantage of being shelf stable when blended with the resin.
The low viscosity and light color of D.E.R. 732 and D.E.R. 736 resins offer viscosity reduction in
epoxy formulations without affecting color of cured compositions. These advantages are not found
with most other flexibilizers.
Figure 1 above shows the effect on viscosity of increasing amounts of flexible resin in blends with
D.E.R. 331. Modifiers which may be reactive as curing agents are often used. Common among these
are polysulfide polymers, triphenyl phosphite, and various polyamides. The latter react readily with
the epoxy.
Nonreactive modifiers
They include;

Dibutyl phthalate.

Nonylphenol.

Pine oil and

Glycol ethers.
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Nonreactive modifiers are not used extensively, as they cause reduction in cured resin properties.
When used, their more common function is to lower cost.
Chief requisites is that they should;

Be compatible with the resin before and after cure,

Not vaporize or foam during cure.

Not migrate excessively from the cured composition.
3.4.3 RESIN FILLERS
The use of fillers in epoxy compositions can lower costs, reduce exotherm, extend life, and achieve
improvement in one or more of the cured resin properties like;
 Improved machinability
 Improved abrasion resistance
 Improved impact strength chopped glass other fibrous materials
 Improved electrical properties mica silica powdered or flaked glass
 Improved thermal conductivity metallic fillers coarse sand alumina
 Improved anti-settling and flow.
Most fillers reduce the coefficient of thermal expansion and shrinkage in proportion to the amount of
filler rather than the type of filler used.
Such improvements are usually achieved at the sacrifice of other mechanical properties.
Fine granular fillers –When fine granular fillers are used the following properties are affected.
They include; Tensile strength.
Flexural strength.
Impact strength
Medium-weight granular fillers may be used at quite higher loadings
They include; powdered aluminum,
alumina, and
silica,
Fibrous and flake fillers. They impart high viscosities at low filler loadings
They include ; Chopped glass strand,
Glass flake,
Mica.
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Heavy fillers may be loaded at ratios up eight times that of medium weight granular loadings.
They include; Powdered iron,
iron oxide,
Coarse sand.
Generally the finer particle size fillers are easier to incorporate, and have fewer tendencies to settle.
Coarse and heavy fillers tend to settle and cake on standing unless some light-weight filler or antisettling agent is also incorporated. Fumed silica compounds are effective as anti-settling and
thixotropic agents.
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CHAPTER 4
4.0 MECHANICAL PROPERTIES
Two important mechanical properties of any resin system are its tensile strength and stiffness. The
two fibres below show results for tests carried out on commercially available epoxy resin, vinyl-ester,
and polyester cured at 20oC and 80oC
3.5
3
2.5
2
Series 1
1.5
Series 2
1
0.5
0
Epoxy
polyster
Vinylester
Figure 6 Tensile modulus comparison graph
After a cure period of seven days at room temperature it can be seen that typical epoxy will have
higher properties than typical polyester and vinyl ester for both strength and stiffness. The beneficial
effect of a post cure at 80OC for five hours can also be seen.
Also of importance to the composition designer and builder is the amount of shrinkage that occurs in
a resin during and following its cure period. Shrinkage is due to their resin molecules rearranging and
reorienting themselves in the liquid and semi-gelled phase. Polyester and vinyl ester require
considerable molecular arrangements to reach their cured state and can show shrinkage up to 8%.
The different nature of the epoxy reaction, however, leads to very little rearrangement and with no
volatile by products being evolved: typical shrinkage of an epoxy is reduced to around 2%.
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The absence of shrinkage is , in part, responsible for the improved mechanical properties of epoxies
over polyester, as shrinkage is associated with built in stresses that can weaken the material. Also
shrinkage through the thickness of a laminate leads to ‘print through of the pattern of the reinforcing
fibres , a cosmetic defect that is difficult and expensive to eliminate.
4.1 DEGRADATION FROM WATER INGRESS
An important property of any resin, particularly in a Marin environment is its ability to withstand
depredation from water ingress. All resins will absorb some moisture, adding to laminates weight,
but what is more significant is how the absorbed water affects the resin and resin fibre bond in a
laminate, leading to a gradual and long term loss in mechanical properties. An epoxy laminate
immersed in water for a period of one year will retain around 90% of its inter-laminar shear strength.
Whereas both polyester and vinyl reins are prone to water degradation due to the presence of
hydrolysable ester groups in their molecular structures, as a result, a thin polyester laminate can be
expected to retain only 65% of its inter-laminar shear strength for the same period.
The elevated temperature soaking gives accelerated degradation properties for the immersed
laminate.
4.2 GELATION, CURING AND POST - CURING
On addition of the catalyst or harder a resin will begin to become more viscous until it reaches a state
when it is no longer a liquid and has lost its ability to flow. This is the gel point. The resin will
continue to harden after it has gelled, until, at some time later, it has obtained its full hardness and
properties. This reaction itself is accompanied by the generation of exothermic heat, which, in turn
speeds the reaction. The whole process is known as the curing of the resin. The speed of cure is
controlled by the amount of accelerator in the epoxy resin and by varying the type, not the quantity,
of hardener in an epoxy resin.
Generally polyester resins produce a more severe heat and faster development of initial mechanical
properties than epoxies of a similar working time.
With both the resin types, however, it is possible to accelerate the cure by the application of heat, so
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that the higher the temperature the faster the final hardening will occur.
This can be most useful when the cure would otherwise take several hours or even days at room
temperature. A quick rule of thumb for the accelerating effect of heat on a reaction is that 10oC
increases in temperature will roughly double the reaction rate. That is, if a resin gels in a laminate in
25minutes at 20oC it will gel at about 12 minutes at 30oC, provided no extra heat occurs.
Curing at elevated temperatures has the added advantage that is actually increases the end mechanical
properties of the material, and many resin systems will not reach their ultimate mechanical properties
of the material, unless the resin is given this post cure, which increases the amount of cross linking of
the molecules that can take place. To some degree this post cure will occur naturally at warm room
temperatures, but higher properties and shorter post cure times will be obtained if elevated
temperatures are used. This is particularly true for material’s softening point for glass Transition
temperature (Tg), which, up to a point, increases with increasing post curve temperatures.
4.3 ADHESSIVE PROPERTIES
Adhesive properties of the resin system are important in realizing the full mechanical properties of a
composite. The adhesion of the resin matrix to the fibre reinforcement or to a core material in a
sandwich construction is important. Epoxy system offer the best performance of all the three resins
considered here. Polyester resins generally have the lowest adhesive properties of the three. On the
other hand, vinly-ester resin shows improved adhesive properties over polyester. Due to this
performance property, epoxy resins are frequently found in many high strength adhesives. This is due
to their chemical composition and the presence of polar hydroxyl and ester group. As epoxies cure
with low shrinkage the various surface contacts set up between the liquid resin and the adherents are
not disturbed during the cure The adhesive properties of epoxy are generally useful in the
construction of honey comp cured laminates where the small bonding surface area means that
maximum adhesion is required.
The strength of bond between resin and fibre is not solely depended on the adhesive property of the
resin system but is also affected by surface coating on the reinforcement fibres.
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4.4 MICRO-CRACKING
The strength of a laminate is usually thought of in terms of how much load it can withstand before it
suffer composition failure. This ultimate or breaking strength is the point it which the resin exhibits
catastrophic breakdown and the fibre reinforcements break. However, before this ultimate strength is
achieved, the laminate will spread through the resin matrix. This is known as ‘transverse microcracking’ and, although the laminate has not completely failed at this point, the breakdown process
has commenced. Consequently, engineers who want a long-lasting structure must ensure that their
laminate do not exceed this point under regular service loads.
The strain that a laminate can reach before micro-cracking depends strongly on toughness and
adhesive properties of the resin system. For brittle resin systems, such as most polyester, this point
occurs a long way before laminate failure, and so severely limits the strains to which laminates can
be subjected. As an example, recent tests have shown that for a polyester/glass roving laminate,
micro-cracking typically occurs at about 0.2% strain with ultimate failure not occurring until2.0%
strain. This equates to a usable strength of only10% of the ultimate tensile strength.
As the ultimate strength of a laminate in tension is governed by the strength of the fibres, these resin
micro-cracks do not immediately reduce the ultimate properties of the laminate. However, in an
environment such as water or moist air, the micro-crack laminate. This will then lead to an increase
in weight, moisture attack on the resin and fibre sizing agents, loss of stiffness and with time
eventually drops in ultimate properties.
Increased resin/fibre adhesion is generally derived from both the resin chemistry and its compatibility
with the chemical surface treatments applied to fibres. Here the well known adhesive properties of
epoxy help laminates achieve higher micro-cracking strains. As it has been previously mentioned,
resin toughness can be hard to measure, but is broadly indicated by its ultimate strain to failure.
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A set of properties of epoxy resins is given in table below which was compelled by JONSON(1979)
from Manufactures literature.
PROPERTY
VALUE
UNITS
Density
1.1-1.4
MgM-3
Young’s modulus
2-6
GNM-2
Poisons ratio
0.38-0.4
ν
Tensile strength
35-100
Mpa
Compressive strength
100-200
Mpa
Elongation to break
1-6
%
Thermal conductivity
0.1
WM-1 oC
Coefficient of thermal expansion(α)
60
10-6 oC
Heat distortion temperature
50-300
o
Shrinkage on curing
1-2
%
C
Table 5; Typical properties of epoxy resins used in composite materials(After Johnson 1979)
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CHAPTER 5
5.0 MECHANICAL PROPERTIES OF EPOXY RESIN/BAGGASSE COMPOSITES
The test piece was subjected to a tensile load. Testing was done under room atmospheric conditions.
A gauge length of 60mm was maintained for all test pieces. This was set as the distance between the
gripping jaws before loading commenced.
The specimens were tested in tension until failure, with the main parameters observed being the
tensile modulus and strength. A complete load deflection plot to fracture was obtained for all
specimens. Tensile strength was obtained by dividing the maximum load the composite would
withstand by the original cross-sectional area.
δuts =
Where 6uts is the ultimate tensile strength in N/m2, Pmax is the maximum load in (N) and A the initial
cross sectional area (mm2). Cross sectional area was calculated by taking an average of three readings
of the pieces measured by a veneer caliper accuracy of 0.05mm the strain calculations were done
with the assumptions that the strain in the machine member was negligible compared to the
specimens strain. The tensile modulus of elasticity was obtained from the slope of the linear portion
of the stress-strain curve. It was as the ratio of the increment stress to the corresponding increment
strain.
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5.1 Flexural strength
Figure 7: 3 point bending test
Flexural strength, also known as modulus of rupture, bend strength, or fracture strength, a mechanical
parameter for brittle material, is defined as a material's ability to resist deformation under load. The
transverse bending test is most frequently employed, in which a rod specimen having either a circular
or rectangular cross-section is bent until fracture using a three point flexural test technique. The
flexural strength represents the highest stress experienced within the material at its moment of
rupture. It is measured in terms of stress, here given the symbol σ. In this project work we used a
rectangular cross-section.
Flexural and Direct Tensile Strengths
The flexural strength would be the same as the direct tensile strength if the material was
homogeneous. In fact, most materials have small or large defects in them which act to concentrate the
stresses locally, effectively causing a localized weakness. When a material is bent only the extreme
fibers are at the largest stress, if those fibers are free from defects, the flexural strength will be
controlled by the strength of those intact 'fibers'.
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However, if the same material was subjected to direct tension then all the 'fibers' in the material are at
the same stress and failure will initiate when the weakest fiber reaches its limiting tensile stress.
Therefore it is common for flexural strengths to be higher than direct tensile strengths for the same
material. Conversely, a homogeneous material with defects only on it surfaces (e.g. due to scratches)
might have a higher direct tensile strength than flexural strength.
5.2 FLEXTURE OF BAGASE EPOXY RESIN COMPOSITES
Introduction
Fig. 8 - Beam of material under bending.
Extreme fibers at B (compression) and A (tension)
Fig. 9- Stress distribution across beam
When an object formed of a single material, like a wooden beam or a steel rod, is bent (Fig. 8), it
experiences a range of stresses across its depth (Fig. 9). At the edge of the object on the inside of
the bend (concave face) the stress will be at its maximum compressive stress value. At the outside
of the bend (convex face) the stress will be at its maximum tensile value. These inner and outer
edges of the beam or rod are known as the 'extreme fibers'. Most materials fail under tensile stress
before they fail under compressive stress, so the maximum tensile stress value that can be
sustained before the beam or rod fails is its flexural strength.
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5.3 MEASURING FLEXURAL STRENGTH
This can be achieved using three point and four point loading as illustrated below;
5.3.1 THREE POINT BENDING TEST
Fig. 10- Beam under 3 point bending
For a rectangular sample under a load in a three-point bending setup (Fig. 10):
σf =
for a rectangular cross section
P is the load (force) at the fracture point
L is the length of the support span
b is width
d is thickness
σf=
π
for a circular cross section
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5.3.2 FOUR POINT BENDING TEST
Fig. 11 - Beam under 4 point bending
For a rectangular sample under a load in a four-point bending setup
where the loading span is one-third of the support span i.e. (1/3L)
σ=
P is the load (force) at the fracture point
L is the length of the support (outer) span
b is width
d is thickness
If the loading span is 1/2 of the support span (i.e. Li - 1/2 L)
σ=
If the loading span is neither 1/3 or 1/2 the support span for the 4 pt bend setup (Fig. 11):
σ=
(
)
Li is the length of the loading (inner) span
5.3.3 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 fibre. Coupling agents are frequently used to improve wettability.
Well “wetted” fibres increase the interface surfaces area. To obtain desirable properties in a
composite. Failure at the interface (called debonding) may or may not be desirable.
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5.3.4 THE FLEXURAL INTER LAMINAR SHEAR STRENGTH (ILSS) OF THE
COMPOSITE
This is the maximum shear stress that a material can withstand before it ruptures, it is calculated
using the equation
σm =
Where:
σm is the ILSS,
P= is the load,
b =is the width and
t= is the thickness of the specimen under test.
The maximum tensile stress was found out form the equation.
τm =
Where τm is the maximum tensile stress and L is the gauge length.
εf=
5.3.5 CALCULATION OF FLEXURAL MODULUS EF
Ef=
Where;
σf = Stress in outer fibers at midpoint, (MPa)
εf = Strain in the outer surface, (mm/mm)
Ef = flexural Modulus of elasticity,(MPa)
P = load at a given point on the load deflection curve, (N)
L = Support span, (mm)
b = Width of test beam, (mm)
d = Depth of tested beam, (mm)
D = maximum deflection of the center of the beam, (mm)
m = The gradient (i.e., slope) of the initial straight-line portion of the load deflection curve,(P/D),
(N/mm
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CHAPTER 6
6.0 PARALLEL ALIGNED FIBRE COMPOSITE
6.1 STIFFNESS PARALLEL TO THE FIBRE
FIG.
When we consider the behavior of continuous and parallel aligned fibre i.e. a composite that is
loaded in the direction of fibre alignment direction, it is assumed that the fibre matrix interfacial
bond is very good such that the deformation of both matrix and the fibres is the same (an isostrain situation). Under these conditions the total load sustained by the composite Fc is equal to
the loads carried by the matrix phase Fm and fibre phase Ff.
i.e.
Fc = Fm+Ff
(1)
We know stress is given by,
F= σ A
(2)
Hence we can write
σc= σmAm+ σfAf
(3)
Now dividing through by Ac which is the total cross-sectional area we get,
σc=σm
+ σf
(4)
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Where,
and
are the area fraction of the matrix and the fibre phase respectively.
If the composite, matrix and fibre phase length are all equal then
=
And so (4) becomes
σc=σmVm+ σfVf
(5)
And basing on on iso-strain assumption,
Ec=εm=εf
(6)
And if each term above is divided by its respective strain it becomes,
σmVm
σfVf
(7)
= εm + εf
Further if composite matrix and fibre deformation are elastic, then
σ
ε
=Ec;
=Em ;
σ
ε
=Ef
(8)
Where; E is the modulus of elasticity for respective phases.
Putting the E’s into above yields
Ecl=EmVm+E fVf
(9a)
Ecl=Em(1-Vf) + EfVf
(9b)
Since the matrix contains only matrix and fibre phases,
Vf+Vm=1
(10)
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The Ecl is equal to the volume fraction weighted average of the moduli of elasticity of the fibre
and the matrix phases. It can also be shown for longitudinal loading that the ratio of the load
carried by the fibre to that carried by the matrices is;
=
6.2 LONGITUDINAL TENSILE STRENGTH
Normal strength is taken as the maximum stress on the stress strain curve,
If we assume εf < εm which is the usual case then the fibres will fail before the matrix. Once the
fibre have fractured the majority of the load that was borne by the fibres is now transferred to the
matrix. This being the case it is possible to adapt the expression for the stress on this type of
composite into the following,
σ*cl =σ*m(1-Vf)+σ*fVf
Here,
σ* is the stress in the matrix at failure and σ*f is the stress of fibre at failure
6.3 STIFFNESS PERPENDICULAR TO THE FIBRE
FIG
A continuous and oriented fibre composite may be loaded in the transverse direction, i.e. the load
is applied at 90 o angle to the direction of fibre alignment
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For this situation the σ to which the composite as well both phases are exposed is the same, or
σc= σm = σf=σ
(13)
This is termed as iso-stress state, also, the strain or deformation of the entire composite εc is
Ec= εmVm+ εfVf
(14)
But, since
=
(
)
+
(
)
Where Ect is the modulus of elasticity in the traverse direction. Now dividing through by σ yields
=
+
This reduces to,
Ect=
(
)
6.4 DISCONTINUOUS AND RANDOMLY ORIENTED FIBRE COMPOSITE
When fibres are not perfectly aligned with the direction of modulus estimate, an orientationefficiency factor k is added to the equation (14)
Ec= KVfεf+Vmεm
0<K<1
For in plane uniformity distributed fibre orientations, the factor is 3/8 when estimating the inplane composite modulus. the factor is 1/5 for three dimensional uniform fibre-orientation
distribution.
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6.5 ULTIMATE TENSILE STRENGTH
6.5.1 Longitudinal tensile strength
Tensile strength in the parallel orientation. This is the resistance of a board material to be pulled
apart parallel to its surface. The maximum load at the time of fracture is divided by the cross
sectional area [width x thickness]of the specimen to give maximum strength.
σuts=
The tensile strength is the value most often quoted from the results of tension test; yet in reality
is the value of the fundamental significance with regard to the strength of a metal. For ductile
metals the tensile strength should be regarded as a measure of maximum load which a metal can
withstand under the very restrictive conditions of the uniaxial loading. This value bears little
relation to the useful of the metal under more complex conditions of stress, which are usually
encountered.
For many years it was customary to base the strength of members on the tensile strength, suitably
reduced by a factor of safety. The current trend is to the more rational approach of basing the
static design of ductile metals on the yield strength. However, because of the long practice of
using the tensile strength to determine the strength of materials, it has become a very familiar
property, and as such it is very useful for the identification of a material in the same sense that
the chemical composition serves to identify a metal or an alloy.
Further, because the tensile strength is easy to determine and is quite reproducible property, it is
useful for the purpose of specification and for quality control of a product. Extensive empirical
correlations between tensile strength and properties such as hardness and fatigue strength are
often quite useful. For brittle materials, the tensile strength is a valid criterion for design.
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For a composite material, once the matrix has cracked the greatest strain that can be carried by
the fibre is denoted by εfmax. If the composite continues to bear increasing loads after the matrix
has visibly cracked and no longer contributes to the strength of the composites, then the ultimate
tensile strength is given by;
σcu=VfEfεfmax
6.5.2 Transverse Tensile Strength
The strengths of continuous and unidirectional fibrous composite are highly anistropic, and as
such composites are normally designed to be loaded along the high strength, longitudinal
direction. However during in-service application transverse tensile loaded can be present.
Under these circumstances premature failure may result in as much as transverse strength are
usually extremely low, it sometimes lies below the tensile strength of the matrix thus in actual
fact, the reinforcing effect of the fibres is a negative one.
Whereas the longitudinal strength is dominated by fibre strength, a variety of factors will have a
significant influence on transverse strength. These factors include properties of both fibres and
the, matrix, fibres matrix bond strength and the presence of voids. The internal bond strength is
an important property of composite boards which is calculated as follows.
σuts=
6uts= ultimate tensile strength
P= maximum load N
b= width of specimen, mm
L =length of specimen mm
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CHAPTER 7
7.0 EXPERIMENT PROCEDURE
7.1 DESIGN AND MANUFACTURE OF MOULDS
FIG. 12(a) 2-D SKECH OF THE MOULD
FIG 12 (b): 3-D MOULD
The figure above shows the design of the frame of the mould used for casting.
The mould consist of a rectangular frame, a base plate and similar plate for mould top as shown
The mould was made from aluminum though one can use timber as well.
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7.2 BAGASSE FIBRE PREPARATION
Fresh bagasse fibers were collected after they were crushed for extracting juice from Mumias
Sugar Company.
The bagasse fibres were boiled in hot water for three hours.
Lime (CaO) was then added during the heating and unwanted organic acids combined
chemically with the lime to form insoluble compounds.
The insoluble compounds were then washed away in clean water. This also ensured sugar
remains were removed.
The reason for eliminating these impurities is that they would otherwise interfere with the
bonding of the composite.
The fibres were then oven dried at 105oCfor 24 hours.
They were then kept safe in polythene bags to ensure no contact with water or moisture.
7.3 PREPARATION OF PURE EPOXY RESIN
The epoxy resin and hardener were both weighed on an electronic balance mixed in the ratio of
3:1 as recommended by the supplier and stirred properly to attain a uniform mix.
7.4 PREPARATION OF THE COMPOSITE SPECIMEN
A thin layer of petroleum jelly was the smeared on the inner surfaces of the moulds.
The mixture of epoxy resin was poured in the mould gradually and carefully spread with the help
of a spatula about 2mm thick.
Then the bagasse fibres were spread evenly as per the volume fraction required.
For particulate fibre composite, the particles were stirred together with the epoxy uniform mix.
This process was repeated and it was made sure that there was even distribution of the fibres in
the resin.
The mould was filled to the brim and care was taken to ensure that the mould laid on a flat
surface.
The excess bubbles were removed by pinching with a sharp needle and allowing breathing time
of approximately 30 minutes.
Finally the cover was put in place and pressure exerted on it by tightening the bolts and nuts
assembly.
The fresh composite was left to cure for 48 hours under normal atmospheric conditions.
Finally the mould was then removed and the composite removed and stored safely for further
test.
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Below are the samples of the specimen prepared in the Laboratory, Fig shows 40%
discontinuously oriented fibre composite, while fig. Shows longitudinally aligned fibre
composite
FIG 40% FIBRES COMPOSITE
FIG 10% PARTICULATE
7.5 POST CURING
The specimens fabricated were placed in the oven for 3 hours at 60oC for post curing to
eliminate any irregularities before testing.
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CHAPTER 8
8.0 RESULTS AND CALCULATIONS
8.1 CALCULATION OF THEORETICAL TENSILE STRENGTH
Parallel and aligned fibre composite
longitudinal loading
Calculation shown here is based on specimen with Vf 10%
σc=σfVf + σmVm
Where:
σc= composite strength
σf= fibre strength
σm= matrix resin strength
Vf= fibre volume fraction
Vm= matrix volume fraction (1-Vf)
σm =Tesile strength of the resin =67.5MPa
Tensile strength of the fibre σf =180-290Mpa (average=235MPa)
Hence:
6c= {(235x106)0.1 + (67.5x106)0.9}
=84.25MPa
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8.2 CALCULATION OF EXPERIMENTAL TENSILE STRENGTH
Parallel and aligned fibre composite
longitudinal loading
The calculation shown here is based as the whole cast plate containing 10% (Vf)
Stress=
Load=6000N
Area=8x10-5 m2
σc=75MPa
8.3 CALCULATION OF THEORETICAL TENSILE STRENGTH
Parallel and aligned fibre composite
Transverse loading
Calculation shown here is based on specimen with Vf 10%
σct= εf Em(1-Vf) + σfVf
σct= composite strength
σf = fibre strength=235MPa(average)
σm=matrix resin strength=67.5MPa(average)
Vf= fibre volume fraction
Em= matrix elastic modulus
Vf=0.1
Em=2-6 GPa
Tensile strength of resin σm=35-100 MPa
Fibre strain εf =
=12x10-3 to
=15.27x10-3 (average=13.635x10-3)
Hence:
σct={13.65x10-3x3x109 x(1-0.1)+(235x0.1)}x106 = 72.64MPa
=60.35MPa
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8.4 CALCULATION OF EXPERIMENTAL TENSILE STRENGTH
Parallel and aligned fibre composite
Transverse loading
The samples calculation shown is based on 10% Vf
Stress σct=
Load=4400N
Area=(10x8)x10-6 m2=80x10-6 m2
σct=
=
Mpa
σct= 55Mpa
8.5 CALCULATION OF THEORETICAL TENSILE MODULUS
Parallel aligned fibre composite
Longitudinally loading
Test piece based on 10% Vf
Ecl = Em(1-Vf)+EfVf
Where:
Ecl= composite tensile modulus under longitudinal loading
Em = matrix tensile modulus
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Ef= fibre tensile modulus
Vm=matrix Volume fraction= (1-vf)
Vf=0.1
Em={2-4} GPa hence 3GPa ( Average)
Ef= {15-19} GPa hence 17GPa (Average)
Ect= {(3x109x0.9)+( 17x109x0.1) = 5.3x109GPa
Ect= 4.4GPa
8.6 CALCULATION OF EXPERIMENTAL TENSILE MODULUS
Parallel aligned fibre composite
Longitudinally loading
Ecl=
σ
ε
Ecl= Composite elastic modulus
σcl= Composite tensile strength
εcl= Composite tensile strain
Ecl=
MPa
.
=4.05GPa
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8.7 CALCULATION OF THEORETICAL MODULUS OF ELASTICITY
Transverse loading
Parallel aligned fibre composite
Ect= {
(
}
)
Ect= composite tensile modulus under transverse loading
Ef= fibre tensile modulus=17GPa
Em= matrix resin tensile modulus=3GPa
Vf = fibre volume fraction=0.1
Vm =1-Vf =0.9
Ect = 3.269GPa
8.8 CALCULATION OF EXPERIMENTAL MODULUS OF ELASTICITY
Parallel aligned fibre composite
Transverse loading
Ect=
Ect=composite elastic modulus loaded in transverse direction.
εct = composite tensile strain
σct= composite tensile strength loaded in transverse direction.
σct=55Mpa
εct=18.3x10-3
Ect=
.
=3.0 GPa
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8.9 CALCULATION OF THEORETICAL MODULUS OF ELASTICITY
Discontinuous and randomly oriented fibre composite.
Ec=KVfEf+VmEm
0<K<1
Ec=KVfEf+(1-Vf)Em
Taking K as 3/8
Ec=composite modulus of elasticity.
Ef= fibre strength=235MPa
Em =matrix strength
Vf= fibre volume fraction
Vm= matrix volume fraction= (1-Vf)
Ec={(0.375x0.1x17x109) + (0.9x3x109)}
=3.34GPa
8.10 CALCULATION OF EXPERIMENTAL MODULUS OF ELASTICITY
Discontinuous and randomly oriented fibre composite
Ec =
Ec =Randomly oriented composite modulus of elasticity
σc =Composite tensile strength=54.11MPa
Ec =
=3.3MPa
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8.11 CALCULATION OF THEORETICAL FLEXURAL STRENGTH
Parallel and aligned fibres
Vf=0.1
σc=σfVf+σm(1-Vf)
σf=Fibre tensile strength =180-290MPa
Mean fibre tensile strength=235MPa
σm =Flexural strength of the matrix=100MPa
σc= (235x.1)+(110x0.9)
=122.5MPa
8.12 CALCULATION OF EXPERIMENTAL FLEXURAL STRENGTH
Three point loading
Parallel and allighned fibres
For 10% volume fraction
σc =
L (span) = 0.06m
P (load) = 830N
b (width) = 0.01m
d (depth) =0.008m
σc =
.
.
.
=116.7MPa
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8.13 DISCONTINUOUS RANDOMLY ALIGNED FIBRES
Three point loading
σc =
L=span=0.06m
P=load=810N
b=width=0.01m
d= depth=0.008m
σc =
.
.
.
=113.9MPa
8.14 FOUR POINT LOADING
Parallel and aligned fibres
The formula used was based on the loading span being ½ that of the support span.
σc=
L=span =0.06m
P=load =1620N
b=width =0.01m
d= depth =0.008m
6c=
.
.
.
=114MPa
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8.15 FOUR POINT LOADING THEORETICAL
Discontinuous randomly aligned fibres
σc =K σfVf+ σm(1-Vf)
Vf =0.1
Mean Fibre strength =235MPa
Flexural strength=110MPa
K=3/8
σc =0.375x235x106 x0.1+110x106 x0.9
=107.8MPa
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CHAPTER 9
9.0 SUMMARY OF RESULTS
Below are the volume fractions used,
9.1 VOLUME FRACTION
SPECIMEN TESTED
VOLUME FRACTION (%)
1
10
2
20
3
30
4
40
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9.2 THEORETICAL TENSILE STRENGTH
Parallel and aligned fibres
Longitudinal loading.
FIBRE VOLUME
FRACTION
%
10
LOAD
N
6000
EXPERIMENTAL
TENSILE
STRENGTH
(MPa)
75
THEORETICAL
TENSILE
STRENGTH
(MPa)
84.3
20
7190
90
30
8385
104
40
9578
119.7
101.0
117.8
134.5
9.3 THEORETICAL TENSILE STRENGTH
Parallel aligned fibres
Transverse loading
FIBRE VOLUME
FRACTION
%
LOAD
( N)
EXPERIMENTAL
TENSILE
STRENGTH
(MPa)
THEORETICAL
TENSILE
STRENGTH
(MPa)
10
4401.077
55.0
60.3
5817.365
72.7
79.7
7233.653
90.4
99.1
8649.94
108.0
119.0
20
30
40
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9.4 THEORETICAL AND EXPERIMENTAL TENSILE MODULUS
Parallel aligned composite
Longitudinal loading
Volume fraction
THEORETICAL
TENSILE MODULUS MPa
EXPERIMENTAL TENSILE
MODULUS MPa
10
4.4
4.05
5.8
5.34
7.2
6.62
8.6
7.92
20
30
40
9.5 THEORETICAL AND EXPERIMENTAL ELASTIC MODULUS
Parallel and aligned fibres
Transverse loading
Volume fraction
THEORETICAL
TENSILE MODULUS GPa
EXPERIMENTAL TENSILE
MODULUS GPa
10
3.26
3.00
3.59
3.31
3.98
3.67
4.47
4.12
20
30
40
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9.6 THEORETICAL AND EXPERIMENTAL ELASTIC MODULUS
Discontinuos and randomly oriented fibres
Volume fraction
THEORETICAL
TENSILE MODULUS GPa
EXPERIMENTAL TENSILE
MODULUS GPa
10
3.34
3.30
3.68
3.63
4.01
3.96
4.35
4.30
20
30
40
9.7 THEORETICAL FLEXURAL STRENGTH
Parallel and aligned fibres
VOLUME FRACTION
THEORETICAL
FLEXURAL STRENGTH (MPa)
10
122.5
20
135.0
30
147.5
40
160.0
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9.8 EXPERIMENTAL FLEXURAL STRENGTH
Three Point Loading
Parallel aligned fibres
VOLUME FRACTION
THEORETICAL
FLEXURAL STRENGTH
(MPa)
EXPERIMENTAL FLEXURAL
STRENGTH (MPa)
10
122.5
116.7
135.0
128.6
147.5
140.5
160.0
152.4
20
30
40
9.9 EXPERIMENTAL FLEXURAL STRENGTH
Three Point Loading
Discontinously Oriented Fibres
Volume fraction
THEORETICAL
FLEXURAL STRENGTH
(MPa)
EXPERIMENTAL FLEXURAL
STRENGTH (MPa)
10
122.5
113.9
135.0
125.5
147.5
137.1
160.0
148.7
20
30
40
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9.10 EXPERIMENTAL FLEXURAL STRENGTH
Four point loading
Parallel aligned fibres
Volume fraction
THEORETICAL
FLEXURAL STRENGTH
(MPa)
EXPERIMENTAL FLEXURAL
STRENGTH (MPa)
10
122.5
114.9
135.0
128.5
147.5
141.1
160.0
149.7
20
30
40
9.11 THEORETICAL FLEXURAL STRENGTH
FOUR POINT LOADING
Randomly aligned fibres
Volume fraction
THEORETICAL
FLEXURAL STRENGTH
(MPa)
EXPERIMENTAL FLEXURAL
STRENGTH (MPa)
10
107.8
104.2
105.6
103.1
103.4
100.0
101.3
98.32
20
30
40
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DISCUSSION
It is evident from the results carried out that the tensile and flexural strength of bagasse/epoxy
composites increases with fibre addition for the case of parallel aligned fibres.O the other hand
the flexural strength showed appreciable decrease in strength with increase in fibre fraction. This
was quite in order with the predictions from the rule of mixtures.
The theoretical values varied from the experimental values and this was expected because of the
defects that lower the strengths in experimental work is bound to be present.
The casting method employed in the fabrication of bagasse/epoxy resin composite resulted in the
formation of voids within the specimens due to entrapped air.
The voids have a negative effect on the composite strength. The two methods of elimination of
air bubbles were; continuous gentle pouring of the resin into the moulds, followed by pinching of
air bubbles using a niddle. However allowing a breath in space of approximately 30 minutes
before covering the composite mixture proved more effective, it is anticipated that the presence
of voids in the composite might have contributed to the scatter observed in the results.
Although the fibres were made to the best of our ability, some fibres were not completely
uniaxially aligned and this would have affected the strength of the individual test pieces. Fibres
were also distributed throughout the cast plate, but as one could expect, such a distribution is
bound to have some degree of non-uniformity. This caused some test pieces to have higher strain
than the others with the same fibre volume fraction. Bagasse fibres consists of fibres from
different leaves and plants and most likely different stages of maturity causing variation in their
properties, some fibres are not of uniform cross-section and this would tend to change the
strengthening effects of the fibre for various test pieces depending on the concentration on thick
medium and thin fibres in that test piece. Un-reinforced and low fibre composites exhibited a
smooth composite fracture surface without protruding fibres, however at higher reinforcements
levels, multiple matrix fracture followed by fibre pullout mode of failure was observed. The
result is an irregular structure fracture surface. It can be noted that by incorporating bagasse
fibres into epoxy resin matrix, a composite material is produced with strength and stiffness close
to that of the fibres and obviously having the chemical resistance property of the plastic matrix.
The high flexural modulus of elasticity values obtained offers some resistance to crack
propagation in any of the existing flaws.
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CONCLUSION
It has bin demonstrated that bagasse fibre can be used to reinforce epoxy resin as the resulting
composite has been found to have very attractive physical and mechanical properties.
Lignocelluloses are attractive material sources for composites because they are light-weight,
economical, and require law amounts of energy for processing.
Also, their growth, use and disposal are generally considered environmentally friendly.
Lignocelluloses will be used in the future to produce a wide spectrum of composite products,
ranging from very inexpensive low-performance characteristics.
As renewable materials, they can be used to replace or extend non-renewable materials such as
those based on petroleum and as a result, the material promises application in many areas. A
relatively new industrial breakthrough for the use of plant fibres is the production of inner panels
for motor vehicles.in this case a plant fibre –based composite has been able to compete with a
glass-fibre-reinforced component as a result of the low price of the plant fibres and their
beneficial properties[low weight and good thermal and sound insulation]. The manufactururing
techniques using moulds for three dimensional products such as car panels can also in principal,
be extended to other product areas within the building sector i.e.[roofing material], furniture,
transportation and packaging industries. Lignocelluloses/thermoplastic composites are a newer
area of lignocelluloses utilization. It is anticipated that interest and commercial development will
continue in this area.
More than enough agricultural fibre residues are available to support composite manufacturing
needs, although the agro-based materials may not have a suitable geographical distribution to
provide an economically feasible endeavor.
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RECOMMENDATION FOR FURTHER RESEARCH:
In this study the highest fibre volume fraction of 40% has been used. This can be further
increased to find out the optimum filler volume fraction.
The fibre matrix bonding can be increased by treating the fibres with acetone and an alkali.
Improvements in the process of bagasse cleaning and surface treatment could increase the
performance of the composite and provide better competitiveness with respect to other materials
in the same structural class.
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REFERENCE
1. Moore,p.h., nuss,k.j. flowering and flowersynchronization.in’sugarcane improvement
through breeding’,dj Heinz,ed.elsevier, Amsterdam.pp 273-311
2. Leslie,n Philips,[editor]design with advanced composite materials,the design councillondon
3. Scotte bader handbook 2003. P3-20
4. R.m rowell,the state of art and future development of bio basesd composites science and
technology towards the 21st century pp 1-10
5. Han j.s and rowell[1997]chemical composition of fibres in paper composites from agrobased resources.r.m rowell,r.a young and j.k rowell.chapter 5,pp83-134
6. Dr.bill Broughton, techniques for monitoring water absorption in fibre reinforced
composites.
7. Bull,t.[2000].the sugarcane plant.in’manual of cane growing’,m Hogarth,p
allsopp,eds.bureau of sugar experimental stations,indooroopilly,Australia.pp71-83
8. Daniels,j.roach,b.t.[1987].taxonomy and evolution in ’sugarcane improvement through
breading’,dj Heinz,ed vol 11. Elsevier,Amsterdam,Netherlands.pp7-84
9. Mackintosh d.2000.sugar milling.in ‘manual of cane growing’,m Hogarth,p
allsopp,eds.bureau of sugar experiment solution,indooroopilly Australia,pp369-377
10. Material science and engineering an introduction,6th edition by William D Calister, Jr.
11. The stress-strain curve.htm
12. Cesar benigna grande costlier.sugarcane extraction and prevention, and long lime pretreatment of bagasse pp353-355
13. Dow Chemical Company Manual
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APPENDIX 1.A
TENSILE STRENGTH
LONGITUDINAL LOADING
Volume
fraction (%)
Depth X10-3m
Breadth X10-3
m
Area x10-6m2
Load (N)
10
8
10
80
6000
Tensile
Strength
(MPa)
75
20
8
10
80
7190
90
30
8
10
80
8385
104
40
8
10
80
9578
119.7
APPENDIX 1.B
DISCONTINOUS ORIENTED FIBRES
Volume
fraction (%)
Depth X10-3m
Breadth X10-3
m
Area x10-6m2
Load (N)
10
8
10
80
4400
Tensile
Strength
(MPa)
55.0
20
8
10
80
5820
72.7
30
8
10
80
7233
90.4
40
8
10
80
8650
108.0
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APPENDIX 2.A
THREE POINT LOADING
FLEXURAL STRENGTH
PARRALLEL ALIGNED FIBRES
Volume
fraction (%)
Depth X10-3m
Breadth X10-3
m
m
Lengthx10-3
m
Load (N)
10
8
10
60
830
Flexural
Strength
(MPa)
116.7
20
8
10
60
915
128.6
30
8
10
60
1000
140.5
40
8
10
60
1085
152.4
APPENDIX 2.B
FLEXURAL STRENGTH
DISCONTINOUS ORIENTED FIBRES
Volume
fraction (%)
Depth X10-3m
Breadth X10-3
m
m
Lengthx10-3
m
Load (N)
10
8
10
60
810
Flexural
Strength
(MPa)
113.9
20
8
10
60
890
125.5
30
8
10
60
975
137.1
40
8
10
60
1057
148.7
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APPENDIX 3.A
FOUR POINT LOADING
FLEXURAL STRENGTH
PARRALLEL ALIGNED FIBRES
Volume
fraction (%)
Depth X10-3m
Breadth X10-3
m
m
Lengthx10-3
m
Load (N)
10
8
10
60
1634
Flexural
Strength
(MPa)
114.9
20
8
10
60
1828
128.5
30
8
10
60
2007
141.1
40
8
10
60
2130
149.7
APPENDIX 3.B
FOUR POINT LOADING
FLEXURAL STRENGTH
DISCONTINOUS ORIENTED FIBRES
Volume
fraction (%)
Depth X10-3m
Breadth X10-3
m
m
Lengthx10-3
m
Load (N)
10
8
10
60
1482
Flexural
Strength
(MPa)
104.2
20
8
10
60
1466
103.1
30
8
10
60
1424
100.1
40
8
10
60
1398
98.32
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