CHAPTER 1 INTRODUCTION -...
Transcript of CHAPTER 1 INTRODUCTION -...
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CHAPTER 1
INTRODUCTION
Composites are combinations of two /more dissimilar materials to
form a new material with enhanced material properties that are not available
in the individual materials alone. The important constituents of composites
are the reinforced phase, the matrix and the interphase (Bisanda et al 2000).
The reinforcing phase may be present in the form of fibers, sheets or particles
and is embedded in the matrix. The matrix phase is continuous and acts as a
load transfer medium to the reinforced phases. Matrices can be polymers,
metals or ceramics (Maries Idicula 2008). Composites are used in all sectors
of industries like transportation, electronic and computer systems, commercial
appliances, construction industries etc.
1.1 REINFORCEMENT
(i) A Reinforcing constituent provides strength and rigidity
(Aziz and Ansel 2004).
(ii) It also provides certain additional properties like heat
resistance or conduction, resistance to corrosion etc,
(iii) The reinforcement may be fibers, whiskers, particulates and
flakes, they are shown in Figure1.1.
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Figure 1.1 Flow Chart of Reinforcement
1.1.1 Fibers
(i) The word fiber is a Latin word, meaning string or thread like
portions, which form the most important class of
reinforcements (Alvarez et al 2003). Fibers are classified
into
1. Natural fiber and
2. Synthetic fiber
(ii) They are flexible and can be spun / twisted for wearing,
braiding, knotting etc, to make the desired products.
(iii) They constitute cellulose; polymer of glucose bonded to
lignin, with varying amounts of other natural materials
(Bachtiar et al 2009).
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1.1.2 Natural Fibers
Natural fibers are vegetable fibers that are derived from plants and
animals. They have been employed in all the civilizations of the world to meet
basic requirements like clothing, construction materials, storage systems etc.
These fibers offer fabulous advantages like low pollution, bio-degradability,
low density and cost effectiveness (Bismarck et al 2005). Some of the
common natural fibers, family names and their annual production are shown
in Tables 1.1and 1.2 respectively.
Table 1.1 Common Natural Fiber Families and Scientific Name
Type General Name Family Name Scientific Name
Bast Fibers
Hemp Cannabaceae Cannabis sativa
Jute Tiliaceae Corchoruscapsularis
Flax Linaceae Linumusitatissimum
Kenaf Malvaceae Hibiscus cannabinus
Roselle Malvaceae Hibiscus sabdariffa
Ramie Urticaceae Boehmerianivea
Leaf Fibers
Abaka Musaceae Musa textilis
Sisal Agavaceae Agave sisalana
Henequen Agavaceae Agave fourcroydes
Pineapple Bromeliaceae Ananascomosus
Banana Musaceae Musa mannii
Fruit Fibers Coir Arecaceae Cocosnucifera
Seed FibersKapok Bombacaceae Ceibapentandra
Cotton Malvaceae Gossypium arboreum
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Table 1.2 Annual Productions of Natural Fibers and Sources
(Plackett et al 2004)
Fiber type Origin World Production 103 Tons
Coir Fruit 100
Banana Stem 200
Bamboo Stem 10,000
Jute Stem 2,500
Hemp Stem 215
Flax Stem 810
Abaca Leaf 70
Kenaf Stem 770
Roselle Stem 250
Ramie Stem 100
Sisal Leaf 380
Sun Hemp Stem 70
Cotton Lint Fruit 18,500
Wood Stem 1, 750,000
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1.1.2.1 Cotton Fiber
(i) Cotton is a soft, stable fiber that grows around the seeds of
the cotton plant, a shrub native to tropical and subtropical
regions around the world (Botelho et al 2003). The cotton
plant, cotton fiber with seed, cultivated cotton fibers and
cotton thread are shown in Figures 1.2 and 1.5.
(ii) Cotton fiber is the most widely used fiber across the world
(Das K et al 2009).
(iii) Cotton fibres are used to produce a number of textile
products, fishing nets, coffee filters, tents etc.
Figure 1.2 Cotton Plant
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Figure 1.3 Cotton Fiber with Seed
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Figure 1.4 Cultivated Cotton Fibers
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Figure 1.5 Threads of Cotton Fiber
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1.1.2.2 Jute Fiber
Jute is a vegetable fiber, which is long and shiny and can be spun
into coarse strong threads. It is obtained from the Stem of two species, viz,
Corchorus Capillaries L (white jute) and C.Uhtoruis L (tosa jute).
White jute is used for making ropes, twines and fabrics. Tosa jute
fiber is softer, silky and stronger than white jute. Jute fibers are hygroscopic
and swell 23% in diameter, 40% in cross-section and 0.06% in length.
Absorption of water modifies the dimensions, and mechanical and electrical
properties. Jute fibers consist of 12-14% lignin, 21-24% hemicellulose, 58-
63% - cellulose and trace amounts of nitrogenous matter, fats, wax and ash
(Cabral et al 2005). The jute plant, extraction of jute fibers, field of jute fibers,
bundle of jute fibers and structure of jute fiber are shown in Figures1.6 -1.10.
The main advantages of jute fibers are:
Renewable
Eco-friendly
Highly stable
Inexpensive
Have low density
Non-abrasive
Have high strength and low elongation
Resistant to fracture
Have Specific strength
Have reduced tool wear
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The disadvantages of jute fibers are that
They are hygroscopic
The Lignin degrades around 200 °C
They are liable to humid climates
They have decreased strength when wet
Figure 1.6 Jute Plant
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Figure 1.7 Extractions of the Jute Fibers from Jute Plant
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Figure 1.8 Field of Jute Fibers
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Figure 1.9 Threads of Jute Fiber
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Figure 1.10 Structure of the Jute Fiber
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1.1.2.3 Hemp Fiber
Hemp is a bast fiber with long slender primary fibers on the outer
portion of the stalk. Hemp has been produced for thousands of years as a
source of the fiber for paper, cloth and building materials. There are two types
of hemp fibers (Bledzki et al 2004). They are
(i) Primary bast fibers
(ii) Secondary bast fibers
(i) Primary Bast Fiber
These fibers make up approximately 70 % of the fibers. They are
long with a high cellulose and low lignin content.
(ii) Secondary Bast Fibers
Secondary bast fibers make up the remaining 30% of the bast
fibers, with medium length and high lignin content. Hemp fibers are used for
making papers, textiles, biodegradable plastics, and in construction industries.
The hemp plant, cultivated hemp, field of hemp fiber and threads of hemp
fibers are shown in Figures 1.11 and 1.14.
Figure 1.11 Hemp Fibers Plant
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Figure 1.12 Cultivated Hemp Fibers Plant
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Figure 1.13 Field of Hemp Fibers
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Figure 1.14 Threads of Hemp Fiber
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1.1.2.4 Sisal Fiber
Sisal is a strong, sturdy, tough and tan-colored fibers that is
prepared from the vascular tissue of the sisal plant. This fiber is resistant to
moisture and heat. It is used for making mats, ropes, carpets etc (Cyras et al
2004 and Garcia et al 2006). The Sisal plant, cultivated sisal, field of sisal
fiber and sisal fiber threads are shown in Figures 1.15-1.18.
Figure 1.15 Sisal Plant
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Figure 1.16 Cultivated Sisal Fibers plant
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Figure 1.17 Field of Sisal Fibers
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Figure 1.18 Threads of Sisal Fiber
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1.1.2.5 Banana Fiber
Banana Fiber is obtained from the edible-fruit bearing plant. The
trunk is removed and the brown-green skin is discarded to get a white portion,
which is processed to get fibers (Elanthikkal et al 2010). The fibers extracted
are dried in sun-light to get white fibers. These fibers can be used for making
a number of products like floor mats, table mats, bags, furnishing etc
(Corrales et al 2007). The banana plant, cut into small disk and banana fibers
are displayed in Figures 1.19 - 1.21.
Figure 1.19 Banana Plants
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Figure 1.20 Cut Banana Tree Trunk into Small Disk-Like Bases
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Figure 1.21 Banana Fibers
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1.1.2.6 Coir (Coconut Fiber)
Coir is derived from the tissues surrounding the seed of the coconut
palm. Coir is strong, light and can withstand heat. Coir is classified into two
types. They are brown fiber and white fibers. Brown fibers are obtained from
mature coconuts, whereas white fibers are extracted from immature green
coconuts (CNF 2009 Islam et al 2010). The coconut tree, coconut fiber with
shell, coconut fibers and coconut ropes are shown in Figures 1.22 - 1.25.
Brown coir is utilised for producing doormats, packaging
applications, brushes, etc (Brahmakumar et al 2005 and Haque et al 2009).
White coir is used for making ropes, fishing nets, decorative items etc.
Figure 1.22 Coconut Tree
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Figure 1.23 Coconut Fibers with Shell
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Figure 1.24 Coconut Fibers
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Figure 1.25 Ropes of Coconut Fiber
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1.1.2.7 Flax Fiber
Flax fiber is extracted from the skin of the flax plant. These fibers
are soft, strong, flexible and lustrous. It is used for preparing high quality
paper, paper for tea bags and packing cigarettes. Apart from the above
applications, it is also used in the production of linen, canvas, ropes and sacks
(Cao et al 2007). The flax plant, cultivated flax, field of flax and flax fiber is
shown in Figures 1.26 - 1.29.
Figure 1.26 Flax Plants
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Figure 1.27 Cultivated Flax Fibers Plant
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Figure 1.28 Field of Flax Fibers Plant
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Figure 1.29 Threads of Flax Fiber
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1.1.3 Chemical Composition of Natural Fibers
Natural fibers are composed mainly of cellulose, hemicellulose,
lignin and pectin. These constituents are widely distributed throughout the
fiber wall, and depend upon the place of origin, production area and variety
(Das et al 2010 and Josep et al 2002).
1.1.4 Chemical Treatment of Natural Fibers
A better understanding of the chemical composition and surface
adhesive bonding of natural fiber is necessary for developing natural fiber
reinforced composites (Islam et al 2009). The interfacial bonding between the
reinforcing fibers and the resin matrix is an important element for improving
the mechanical properties of the composites. Realizing this, several authors
(Ray et al 2001) have focused their studies on the treatment of fibers to
improve the bonding with the resin matrix (Deng et al 2010). The mechanical
properties of the composites are controlled by the properties and quantities of
the individual component and by the character of the interfacial region
between the matrix and the reinforcement. Lack of good interfacial adhesion
makes the use of cellular fiber composites less attractive (Ismail et al 2002).
Often the interfacial properties between the fiber and polymer matrix are low,
because of the hydrophilic nature of natural fiber which reduces its potential
of being used as reinforcing agents. Hence, chemical modifications are
considered to optimize the interface of fibers. Chemicals may activate
hydroxyl groups or introduce new moieties that can effectively interlock with
the matrix. There are various chemical treatments available for the fiber
surface modification (Doan et al 2004). Chemical treatments including alkali,
silane, acetylation, benzoylation, acrylation, isocynates, maleated coupling
agents (Doan et al 2005), permanganate treatment, which are discussed in
detail.
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1.1.4.1 Alkaline Treatment
Alkaline treatment is done on natural fibers to disrupt the hydrogen
bond in the network structure resulting in increased surface roughness.
Certain amounts of lignin, wax and oil, covering the outer surface of the fiber
cell wall are eliminated by this treatment (Gassan and Bledzki 1999). Apart
from this, it depolymerizes the cellulose and promotes the ionization of the
hydroxyl group to the alkoxide. The reaction of alkali treatment with fiber is
shown in Figure 1.30.
Figure 1. 30 Reaction of Alkali Treatment with Fiber
1.1.4.2 Acetylation of Natural Fiber
Acetylation causes the plasticization of cellulose fibers. The
reaction generates acetic acid as a by-product, which should be eliminated
before further use (Haque et al 2010 and Herrera et al 2005). Acetylation
decreases the hygroscopic nature of the natural fiber, and therefore, it can be
well accommodated in the fiber reinforced composites. The reaction of
acetylation treatment with fiber is shown in Figure 1.31.
Figure 1.31 Reaction of Acetylation Treatment with Fiber
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1.1.4.3 Permanganate Treatment
Permanganate treatments are done by using various concentrations
of the KMnO4 solution. This treatment decreases the hydrophilic nature of
the fibers, and therefore, reduces the water absorption behavior of the
composite prepared by these fibers. The reaction of permanganate treatment
with fiber is shown in Figure 1.32. (Joseph et al 2003 and Kamakar et al
2007).
Figure 1.32 Reaction of Permanganate Treatment with Fiber
1.2 MATRIX MATERIAL
When they are in a fibrous form many materials exhibit very good
strength properties, but to achieve these properties the fiber should be bonded
in 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 the ability to deform
easily under applied load, transfer the load on to the fibers and evenly
distribute the stress concentration. A study of the nature of the bonding forces
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in laminates indicates, that upon initial loading there is a tendency for the
adhesive bond between them, that accounts for the high strength properties of
the laminates. The polymer matrix binds the fibers (Klaus et al 2012 and
Klemm et al 2011). They are thermoplastics and thermosetting. The
classification of matrices is shown in Figure 1.33.
Figure 1.33 Classifications of Matrices
1.2.1 Polymer Matrix Material
Polymer matrices are considered as an ideal material since they can
be easily processed, possess light weight and contribute good mechanical
properties. There are two kinds of polymer materials, namely thermoplastic
polymer and thermoset polymer (Ku et al 2011). The classification of polymer
matrix materials is shown in Figure 1.34.
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Figure 1.34 Classifications of Polymer Matrix Materials
1.2.1.1 Thermoplastics
Thermoplastic matrix materials have one or two dimensional
molecular structure and tend to soften at an elevated temperature, and roll
back their properties during cooling (Brostow and Lobland 2006). The best
examples of this kind are polyethylene, polypropylene, polystyrene, nylons,
polycarbonate, polyacetals, polyamide-imides, polyether, ether ketone,
polysulfone, polyphenylene sulfide, polyether imide etc (Brydson 1999).
1.2.1.2 Thermosetting
Thermoset matrix materials have a well bonded 3-d molecular
structure. They decompose instead of melting on hardening (Generi and Vasu
2000). The examples are epoxides, polyesters, phenolics, ureas, melamine,
silicone and polyimides.
1.2.2 Epoxy
Epoxy resins were first used in composites for application in the
early 1950s. This family of oxirane containing polymers can be made from a
wide range of starting components, and provide a broad spectrum of
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properties. Their good adhesion characteristics with glass, aramid and carbon
fibers have resulted in remarkable success as matrix materials for fiber
composites. They also have a good balance of physical, mechanical and
electrical properties and have a lower degree of cure shrinkage than other
thermosetting resins, such as polyester and vinyl ester resins (Lu et al 2006).
Other attractive features for composite application are relatively good hot wet
strength, chemical resistance, dimensional stability, and ease of processing
and low cost (Nishino and Arimoto et al 2005). Epoxy resins are
characterized by the existence of the epoxy group which is a three membered
ring with two carbon atoms and one oxygen. Epoxy resins (Figure 1.35) can
be classified into six different types:
i) Bisphenol A based glycidyl esters
ii) Glycidal ether
iii) Glycidal amines
iv) Novolacs
v) Brominated resins
vi) Cycloaliphatic
Figure 1.35 Structure of Epoxy Resin
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1.3 INTERFACE
The interface is a bounding zone where a discontinuity occurs,
physical, mechanical and chemical. Fibers are wetted by the matrix and to
increase the wettability coupling agents are added. Well “wetted” fibers
increase the interface surfaces area. To obtain the desirable properties in a
composite, the applied load should be effectively transferred from the matrix
to the fibers via the interface (George et al 2001 and Ghosh 2004). This
means that the interface must be large and exhibit strong adhesion between
the fibers and the matrix. Failure at the interface (called de-bonding) may or
may not be desirable (Chitta Rajan 2010).
1.4 CLASSIFICATION OF COMPOSITES
1.4.1 Based on Matrix Material
Based on the matrix materials composites can be classified into
three types. They are
1. Polymer Matrix Composites (PMC)
2. Metal Matrix Composites ( MMC)
3. Ceramic Matrix Composites ( CMC)
1.4.1.1 Polymer Matrix Composites (PMC)
A Polymer matrix composite (PMC) consists of a polymer matrix
combined with a fibrous/particulate reinforcing phase. PMCs are very popular
due to their low cost and simple fabrication methods.
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PMCs are the most developed composite material group, and have
found widespread applications across the globe. The PMC can be easily
fabricated into large complex shape (Generi and Vasu 2000).
The most common polymers employed for PMC are polyester,
vinylester, epoxy, phenolic, polyimmido, polyamido, polypropylene and
others. The reinforcement materials are often fibers and grounded materials.
1.4.1.2 Metal Matrix Composites (MMC)
Metals are durable materials, and have been widely exploited
across the world. When metals are combined with reinforcements such as B,
C, Al2O3, SiC etc, to get metal matrices composites. MMCs are light in
weight, exhibit good stiffness and low specific weight. Apart from these they
also have excellent properties, they have good fracture toughness, thermal
stability, ductility, and increased elevated temperature tolerance.
1.4.1.3 Ceramic Matrix Composites (CMC)
Ceramics are chemically stable and crystalline materials. They are
made by the action of heating and subsequent cooling, from compounds of
metallic or non-metallic elements. Ceramic matrix composites are prepared
by combining a ceramic matrix with suitable fibers such as poly crystalline/
amorphous inorganic fibers/ carbon fibers. Thermosetting and thermoplastics
materials can withstand temperatures upto 300 °C while metals and alloys can
be utilized upto 900 °
C. Above all materials ceramics can withstand
temperatures above 1500° C. Therefore this clearly indicates that ceramics are
the only material which can be used upto 1500 °C ( Nishino and Kotera 2003).
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The most commonly employed ceramic matrix materials include
glass-ceramics and ceramics such as carbon, SiC, silicon nitride, aluminides
and oxides.
1.4.2 Classification of Composites Based on Reinforcement Material
As the word indicates, it provides the strength that makes the
composite what it is. But they also serve certain additional purposes like heat
resistance or conduction, resistance to corrosion and provide rigidity.
Reinforcement can be made to perform all or one of these functions as per the
requirements (Nishino et al 2004).
A reinforcement that embellishes the matrix strength must be
stronger and stiffer than the matrix and should be capable of changing the
failure mechanism of the composite (Srinivasan 2009).
1.4.2.1 Fiber Reinforced Composites
In fiber reinforced composites fiber serves as the reinforced/
dispersed phase. The fiber generally occupies 30% to 70% of the matrix
volume in the composites. The fibers may be in the chopped form or woven
(Figure 1.36). To enhance the bonding between the fiber and matrix they are
treated with starch, gelatin, oil or wax. The most common natural fibers used
for the fabrication composites are jute, hemp, banana, flax, cotton etc, for
advanced composite material, glass fibers, aramid carbon etc are utilized
(Mwaikambo and Ansell 2002). The continuous and short fiber is shown in
Figure 1.37.
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Figure 1.36 Aligned, Random and Woven Fibers
Figure 1.37 Continuous and Short Fibers
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1.4.2.2 Particulates Reinforced Composites
Particulates are uniformly dispersed in a softer ductile matrix. The
particulates provide desirable material properties. Particulate reinforced
composites offer several advantages and are usually produced by injection
moulding technique (Orts et al 2005). Particle reinforced composites (Figure
1.38) are classified into a) Large particle composites and b) Dispersion
strengthened composites.
a) Large Particle Composites:
Large particle composites consist of large sized particles embedded
in a relatively soft matrix. The matrix and the reinforced particles share the
load. A typical example is concrete.
b) Dispersion Strengthened Composites:
Dispersion strengthened composites contains extremely small sized
particles in the range of 10-100 nm. These particles increase the particle-
matrix interactions at the atomic level thereby enhancing the strength of
matrix against deformation.
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Figure 1.38 Particle reinforced composites
1.4.2.3 Laminates
Laminate composites are consists of layers of materials which are
held together by matrix. These layers are arranged alternative fashion for the
better bonding between reinforcement and the matrix. These laminates can
have uni-directional or bi-directional orientation of the fiber reinforcement
according to the application of the composite (Mao et al 2010 and Metha et al
2005). The different types of composite laminates are unidirectional, angle-
ply, cross-ply and symmetric laminates.
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1.5 LITERATURE SURVEY
1.5.1 Jute Fiber Reinforced Composites
Boopalan et al (2012) compared the mechanical properties of jute
and sisal fiber reinforced polymer composites, and found that the jute fiber
reinforced composites possessed good mechanical properties than sisal fiber
reinforced composites.
Kabir et al (2010) studied the effect of benzenediazonium salt in
alkaline medium on the mechanical properties of jute fiber reinforced
polypropylene composites. Except elongation all the mechanical properties
were found to be exceptionally good than the raw jute polypropylene
composites. The elongation at break of treated jute polypropylene composite
decreased to a large extent as compared to that of polypropylene.
Rout et al (2011) investigated the effect of the addition of surface
modified jute fiber on the mechanical properties of polyester. Significant
improvement in tensile properties was observed in the case of alkali treated
composites whereas better flexural strength was observed in the case of
bleached jute-polyester composites.
Alves (2010) reported the effects of the jute fiber treatments on the
mechanical performance of the composite materials. The surface of the jute
fibers was modified by drying and bleaching/drying treatments to improve the
wetting behavior of the polar polyester, improving the mechanical properties
of the composites. Finally, jute composites were compared with glass
composites and results show that the jute fiber treatments imply a significant
increase of the mechanical properties of the composites without damaging
their environmental performances.
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The effect of coupling agent on abrasive wear behaviour of
chopped jute fiber-reinforced polypropylene composites was studied by Navin
Chand (2006). The use of coupling agent gave better wear resistance as
compared to without the use of coupling agent.
Mubarak A. Khan et al (2001) performed the effect of
pretreatment with UV radiation on physical and mechanical properties of
photo cured jute yarn with 1, 6-hexanediol diacrylate (HDDA). UV radiation
pretreatment improved the mechanical properties. The tensile strength and
modulus increased upto 84% and 132% respectively than that of virgin, jute
yarn. An experiment involving water absorption capacity shows that water
uptake by treated samples was much lower than that of the untreated samples.
During the weathering test, treated yarns exhibited less loss of mechanical
properties than untreated yarns.
Rana and Jayachandran (2001) investigated the role of jute
composite as wood substitute. The different methods of jute composite
manufacture with its potentials and prospects are also described.
The processing and characterization of short-fiber reinforced
jute/poly butylene succinate biodegradable composites was studied by Ishiaku
(2006). The results revealed that elongation at break and toughness are most
sensitive to the presence of the weld-line whereas flexural properties are least
sensitive.
Moisture absorption, tensile strength and microstructure evolution
of short jute fiber/polylactide composite in hygrothermal environment was
studied by Rui-Hua Hu (2010). The results reveal that the moisture absorption
and aging process can be effectively retarded by coating. The molecular
weight measurement by gel permeation chromatography (GPC) indicated that
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the PLA matrix was severely degraded in hygrothermal environment. Tensile
strength severely decreased after aging.
Sahari et al (2011) reported the natural fiber reinforced
biodegradable polymer composites. These materials have the capability to
fully degrade and compatible with the environment.
Saha et al (2010) reported the jute fiber reinforced polyester
composites by dynamic mechanical analysis. It is also observed that
incorporation of jute fiber (both unmodified and modified) with the
unsaturated resin reduced the tan peak height remarkably.
Sridhar et al (2011) reported the mechanical properties of jute polyester
composites. The tensile, flexural and impact properties of unidirectional and
bidirectional laminates of jute fiber-polyester composites and the mechanical
properties of glass-jute-polyester composites are reported. The effects of
lignin coated bidirectional jute fiber reinforcement composites gives better
mechanical properties than uni directional jute fiber reinforced composites.
ChandanDatta et al (2012) reported that the mechanical and
dynamic mechanical properties of jute fibers–Novolac–epoxy composite
laminates. It was found that jute fiber reinforced composite using Novolac-
epoxy resins exhibit increased stiffness without sacrificing their ductility.
JochenGassan, and Andrzej K. Bledzki (2004)dipictedthe effect of
moisture content on the properties of silanized jute-epoxy composites. The
introduction of the coupling agent distinctly influences the mechanical
properties of the composite: Dynamic modulus was doubled, damping was
reduced by about 50%, and the Wöhler curves showed fatigue limits increased
by about 20%. The investigations pointed out further that the moisture uptake
of composites with silanized fibers was reduced by about 10–20%. Moisture
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at equilibrium and kinetics of absorption increase with increasing fiber
content. Finally, the application of the coupling agent caused a reduction of
moisture effects on the mechanical properties. Tensile strength, tensile
modulus, and fatigue strength under repeated tensile stress were reduced up to
30%. This tendency was not duplicated in the results for flexural strength and
flexural modulus.
Joshi et al (2001) compared life cycle environmental performance
of natural fiber composites with glass fiber reinforced composites and found
that natural fiber composites are environmentally superior in the specific
applications studied.
Shah and Lakkad (2008) compared the mechanical properties of
jute-reinforced and glass-reinforced composites. The results shows that the
jute fibers, when introduced into the resin matrix as reinforcement,
considerably improve the mechanical properties, but the improvement is
much lower than that obtained by introduction of glass and other high
performance fibers. Hence, the jute fibers can be used as reinforcement where
modest strength and modulus are required. Another potential use for the jute
fibers is that, it can be used as filler, fiber, replacing the glass as well as the
resin in a filament wound component. The main problem in this work is that
it is difficult to introduce a large quantity of jute fibers into the JRP laminates
because the jute fibers, unlike glass fibers, soak up large amount of resin. This
problem is partly overcome when hybridsing with glass fibers is carried out.
Jute fibers were subjected to alkali treatment with 5% NaOH
solution for 0, 2, 4, 6 and 8 h at 30 °C by Ray et al (2009). The fibers after
treatment were find, having less hemicellulose content, increased crystallinity,
reduced amount of defects resulting in superior bonding with the vinylester
resin.
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Jute fibers were treated with alkali (NaOH) solution (Sahaet al
2010). The treatments were applied under ambient and elevated temperatures
at high pressure steaming conditions. The results indicated that the uniaxial
tensile strength increased up to 65% for alkali-steam treatment. The
treatments without steaming were not as effective as Physico-chemical
characterization of fibers showed that the increase in tensile strength was due
to the removal of non-cellulosic matters like lignin, pectin and hemicellulose.
Jawaid et al (2011) studied the chemical resistance, void content
and tensile properties of oil palm/jute fiber reinforced polymer hybrid
composites. It is found from the chemical resistance test that all the
composites are resistant to various chemicals. It was observed that marked
reduction in void content of hybrid composites in different layering pattern.
From the different layering pattern, the tensile properties were slightly higher
for the composite having jute as skin and oil palm EFB as core material.
Effect of fabric treatment and filler content on jute polyester
composites was done by Kanakasabai et al (2007). It was observed that due to
fabric treatment, the mechanical properties were improved significantly.
Alkali treatment was found to reduce moisture absorption and the effect of
calcium carbonate on the mechanical performance of the composite is not
significant.
Wang et al (2009) reported the preparation and characterization of
micro and nano fibrils from jute. This technique includes chemical (room
temperature alkaline, acid steam, and 80 °C alkaline) and physical (high
pressure steam) treatments of natural fibers. The effects of chemical and
physical treatments on the morphological development of jute fibers from
micro-to nano-scale were observed by using scanning electron microscopy
(SEM). Two advantages were found. One is the long strands of natural fibers
keep their length by special acid steam treatment, but the traditional acid
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solution treatment makes the length of natural fibers short. Another one is the
high pressure steam treatment that made jute fibers nano-fibrils.
Bhatnagar and Sain (2009) reported the processing of cellulose
nano fiber-reinforced composites. Cellulose nano fibers are obtained from
various sources such as flax bast fibers, hemp fibers, kraft pulp, jute and
rutabaga, by chemical treatments followed by innovative mechanical
techniques. The nano fibers thus obtained have diameters between 5 and 60
nm. The ultrastructure of cellulose nano fibers is investigated by atomic force
microscopy (AFM) and transmission electron microscopy (TEM). The
cellulose nano fibers are characterized in terms of crystallinity. Reinforced
composite films comprising 90% polyvinyl alcohol and 10% nano fibers are
also prepared. The comparison of the mechanical properties of these
composites with those of pure PVA confirmed the superiority of the former.
The Jute as raw material for the preparation of microcrystalline
cellulose performed by Sarwar Jahan (2010). Cellulose was extracted at a
yield of 59.8% from jute fibers based on the formic acid/peroxy formic acid
process at an atmospheric pressure. The amounts of dissolved lignin and
hemicelluloses were determined in the spent liquor. The results showed that
the spent liquor contained 10.6% total sugars and 10.9% lignin (based on
jute). Microcrystalline cellulose (MCC) was further prepared from the jute
cellulose based on the acid hydrolysis technique. A very high yield, 48–52.8%
(based on the jute raw material) was obtained.
Das (2011) reported the physico-mechanical properties of the jute
micro/nanofibril reinforced starch/polyvinyl alcohol biocomposite films. Jute
micro/nanofibrils (JNF) were prepared from jute by acid hydrolysis route.
Starch/polyvinyl alcohol (PVA) based biocomposite films reinforced with
JNF at different loading of 5, 10 and 15 wt.% were prepared by solution
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casting method, incorporating glycerol as a plasticizer. The 10 wt.% JNF
loaded films exhibited best combination of properties.
1.6 SCOPE AND OBJECTIVES
1) To prepare the nano jute fibers from jute fiber
2) To characterize the nano jute fiber by FTIR and SEM
analysis
3) To fabricate various wt. % of (1%, 2%, 3%, 4%, 5%, 6%, 7%,
8 %) raw jute fiber reinforced epoxy polymer composites
4) To fabricate various wt. % of (1%, 2%, 3%, 4%, 5%, 6%, 7%,
8 %) nano jute fiber reinforced epoxy polymer composites
5) To evaluate the mechanical properties (Tensile, Flexural,
Impact and Hardness) of the prepared composites samples
6) To evaluate the dynamic mechanical analysis (DMA), thermo
gravimetric analysis (TGA), heat deflection temperature
(HDT)
7) To evaluate the water absorption studies
8) To characterize the composites samples by TEM, AFM, and
X-Ray Diffraction
9) To compare the raw jute fiber and nano jute fiber reinforced
epoxy polymer composites