Mtech2nd phase report.docx

7/30/2019 Mtech2nd phase report.docx

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DEPT. OF MECHANICAL ENGG. M.TECH (MMD) N.C.E.T

SYNOPSIS

M.Tech.(Machine Design)

Submitted to

Visvesvaraya Technological University, Belagaum

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Title of the project : ANALYSIS AND CHARACTERIZATION OF HYBRID

COMPOSITES

Name of the student : Hemanth K, 4thsem

M.Tech (Machine Design)

N.C.E.T, Bangalore

University seat number : 1NC10MMD76

Name of the guide : (1) Internal guide: Dr.Keerthi Prasad K.S

Professor Department of Mechanical Engineering

N.C.E.T, Bangalore.

(2) External guide: Mr.Ravikumar M

Lecture in Mechanical Engineering Department

SJCIT, Chickaballapura

Place of work : (1).Nagarjuna College of Engineering and Technology

Mudgurki Venkatagiri kote post, Devanahalli Taluk.

(2).BGS R&D Center, SJCIT, Chickaballapura


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SYNOPSIS

Over the last thirty 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 niche applications. There has been an expanding search for

new material with high performance at affordable costs in recent years. With growing

environmental awareness, this search is particularly focused on eco-friendly materials. Generally

composite is one which is light weight and high strength. The fibers which are currently used in

commercial hybrid composites combinations are glass, sisal, hemp, aramid, boron, carbon and

Kevlar.

The various properties of hybrid composite made of synthetic fiber and natural fibers

have been extensively studied. The main focus of this study will be development of hybrid

composites using glass and hemp fiber made of hand lay-up process. The developed hybrid

composites will subject to physical and mechanical properties using standard procedure.

The most widely used reinforcement is synthetic fiber (Glass fiber) because of its low

cost, high tensile strength and impact strength, light weight and good corrosion resistance. In

addition, glass is eco-friendly, glass as reinforcement has proved its immense potential in

numerous composites. A combination of low density hemp and high stiffness glass is expected to

bring numerous advantages in composite. Very limited work has been reported on mechanical

and environmental properties of hybrid composite made of hemp and glass fiber as composite

with epoxy as matrix.


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INTRODUCTION

Composite Materials

Over the last thirty 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 niche 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.

A composite material can be defined as the material that is obtained by judicial

combining of two or more dissimilar materials, having different physical and electrical

properties, in such a way that the resultant material properties are superior to any of the parental

one. Composites are usually made of two phases-one is reinforcement phase and other is matrix

phase.

Composites are usually made of two phases-one is reinforcement phase and other is

matrix phase. Development of new composites and new applications of composites is

accelerating due to the requirement of materials with unusual combination of properties that

cannot be met by the conventional monolithic materials. Actually, composite materials are

capable of covering this requirement in all means because of their heterogeneous nature.


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Properties of composites arise as a function of its constituent materials, their distribution, and the

interaction among them and as a result an unusual combination of material properties can be

obtained.


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Objectives:

Study the merits and demerits of extending hybrid composite commercially available inmarket.

Preparation of new hybrid composite using natural fiber and synthetic fiber as rawmaterial with commercially available epoxy matrix for few volume fraction of

reinforcement.

To evaluate the mechanical properties of hybrid composite. Analysis of hybrid composite using software.


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LITERATURE REVIEW

Types of fibers

Fibers are class of hair-like materials that are in discrete elongated pieces, similar to pieces of

thread (Natural, 2007). They can be spun into filaments, thread or rope. They can be used as a

component of composite materials. Fiber can be classified in to two main groups, which are

man-made fiber and natural fiber. In general, natural fibers can be subdivided as to their origin

such as plants, animals, or minerals; while man-made fibers can be subdivided to synthetic and

natural polymers.

The first fibers used by man were natural fibers such as cotton, wool, silk, flax, hemp and sisal.

The first man-made fiber was probably glass (Cooke, 1989). Both natural and synthetic fibers

(commonly known as man-made fibers) are now available and always being used as fillers in

making a good properties of composites. The major fibers used till now can be classified into the

groups given in Figure

Classification of Fibers (Cooke, 1989)


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Reinforcing fibers in a single-layer composite may be short or long compared to its overall

dimensions.The long fibers and short fibers are called continuous fibers and discontinuous fibers,

respectively (Agarwal and Broutman, 1990). The continuous fibers in a single-layer composite

may be all aligned in one direction to form a unidirectional composite. The unidirectional

composites are very strong in the fiber direction but are generally weak in the direction

perpendicular to the fibers. The continuous reinforcement in a single layer may also be provided

in a second direction to provide more balanced properties [1].

Synthetic fibers

Synthetic fibers are the result of extensive research by scientists to improve upon naturally

occurring animal and plant fibers used in making cloth and rope (Synthetic, 2007). A large

number of synthetic fibers with a variety of properties have been produced from polymers by

various spinning techniques, including melt, dry, wet and emulsion spinning. Before synthetic

fibers were developed, artificial (manufactured) fibers were made from cellulose, which comes

from plants. At the beginning of the twentieth century, synthetic fibers started supplementing and

replacing natural fibers. The first trulysynthetic fiber was nylon, followed by polyesters,

polyacrylics and polyolefins. Also synthetic elastomeric, glass and aramid fibers became

important commercial products (Cooke, 1989).

Synthetic fibers are now available, ranging in properties from the high-elongation and

low-modulus elastomeric fibers, through the medium-elongation and medium-modulus fibers

such as polyamides and polyesters, to the low-elongation, high-modulus carbon, aramid and

inorganic fibers (Hannant, 1989). With such a wide variety of synthetic fibers available, the

volume of synthetic fibers consumed in worldwide is now greater than that of natural fibers.

Most synthetic fibers have relatively smooth surfaces and they are frequently subjected to

various mechanical and heat-setting processes to provide crimp (Cooke, 1989).

The modern synthetic fiber that was made from older artificial materials and become the most

common of all reinforcing fibers for polymer matrix composites is glass fiber (Agarwal and

Broutman, 1990). Glass fiber is the dominant fiber and is used in 95 % of cases to reinforce


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thermoplastic and thermoset composites (Mohanty et al., 2005). The principal advantages of

glass fibers are low cost and high strength compared with others synthetic fibers. The

disadvantages are low modulus and poor adhesion to Polymer matrix resins, particularly in the

presence of moisture.

Natural fibers

Natural fibers are subdivided based on their origins, for example vegetable/plants, animals, or

minerals. Vegetable or plant fibers include bast or stem fibers, leaf or hard fibers, seed, fruit,

wood, cereal straw and other grass fibers (Alexander et al., 2005). According to Jeronimidis

(1989), plants can stand up because of cellulose and lignin. Structural materialsin animals are

mainly made of proteins such as collagen, elastin and keratin in combination with various

polysaccharides, calcium minerals (in bone and teeth) or complex phenolic compounds (in hard

insect cuticles). Mineral fibers are naturally occurring fiber or slightly modified fiber procured

from minerals. Mineral fibers such as asbestos fibers had been used historically for insulating

houses. However, since January 1997, to provide protection of workers and consumers, the

manufacture and transformation of asbestos fibers became forbidden (Bilba et al., 2007).

Mechanical properties of natural fibers

The mechanical properties and physical properties of natural fi bers vary considerably

depending on the chemical and structural composition, fi ber type and growth conditions.

Mechanical properties [2] of plant fibers are much lower when compared to those of the most

widely used competing reinforcing glass fibers. However, because of their low density, the

specifi c properties (property-to-density ratio), strength, and stiffness of plant fibers are

comparable to the values of glass fibers [7].


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FABRICATION OF COMPOSITE

Basic Raw materials

1. Reinforcing material2. Matrix material

REINFORCEMENTS

These are fibrous materials, when introduced into polymer matrix produce a dramatic

improvement in physical properties of a composite. Reinforcement improves overall mechanical

properties of the matrix. The reinforcing filler usually takes the form of fiber but particles (for

e.g. Glass spheres) are also used. A wide range of amorphous and crystalline materials can be

used as reinforcing fibers. These include glass, carbon, boron and silicon. In recent years, fibers

have been produced from synthetic polymers for e.g. Kevlar fibers Glass in the form of fibers is

relatively inexpensive and is the principal form of reinforcement used in plastics. Drawing of

continuous stands of glass from an orifice in the base of an electrically heated platinum crucible,

which contains molten glass, produces the fibers. The earliest successful glass reinforcement had

a calcium-alumina borosilicate composition developed specifically for insulation purpose (E-

glass).

The use of reinforcement fibers can result in the following changes.

Increase in modulus of elasticity and stiffness Lower shrinkage Low temperature dependency of mechanical and physical properties Increase in tensile, compressive and flexural strength.


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Fiber reinforced composites

Glass fiber

Fiberglass or glass fiber is material made from extremely fine fibers of glass. It is used as

a reinforcing agent for many polymer products, the resulting composite material, properly known

as Fiber-Reinforced Polymer (FRP) or Glass-Reinforced plastic (GRP), is called fiberglass in

popular usage. Fiberglass is shown in fig. 2.3.

Glass fiber

Unidirectional Bi-directional

Discontinuous FiberWoven


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Hemp fiber

Hemp fiber is one of the important lignocellulosic bast fiber and has been used as

reinforcement for industrial applications. It is one of the inexpensive and readily available best

natural fibers and hemp-fiber reinforced polymer composite products have gained considerable

attraction for automotive interior products.

Hemp Fiber


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MATRIX

The matrix is the material that gives body and grips or holds the reinforcements of the

composites together, and is usually of lower strength than the reinforcement. The matrix must be

capable of being forced around the reinforcement during some state in manufacture of

composite. Typically, composite material is formed by reinforcing fibers in matrix resin is shown

in fig Resign is organic polymer used as a matrix to contain fibrous reinforcement in composite

material or as an adhesive.

Formation of composite material using fibers and resin

The purpose of matrix is to provide:

Load transfer to fibers Dimensional stability Fiber support Protection Good surface finish quality


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Lapox L-12(Epoxy)

Lapox L-12 is a liquid, unmodified epoxy resin of medium viscosity which can be used

with various hardeners for making reinforced composite and laminates. The choice of hardener

depends upon the processing method to be used and on the properties required of the cured

composite.

Hardener K-6

Hardener K-6 is a low viscosity room temperature curing aliphatic amine curing agent. It

is commonly employed for civil engineering system where low viscosity and fast setting at

ambient temperature is desired.

3.5.3 Typical Properties

Epoxy Resin( Lapox L-12)

Appearance ------- Clear pale yellow liquid

Epoxy Value eq/kg 5.25-5.4

Hydrolysable chlorine % .1max

Viscosity at 25

mPas 10,000-12,000

Volatile content % .55max

Hardener K-6

Appearance -------- Clear pale yellow liquid

Viscosity at 250

mPas 10-23

Refractive Index 1.4940-1.5000

Water content % 1max


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FABRICATION BY HAND LAY-UP TECHNIQUE

In this process resins are impregnated by hand into fibers which are in the form of woven

or bonded fabrics. Hand layup process usually accomplished by rollers or brushes.

The composite plates from which the test specimens were fabricated by employing the

traditional Hand layup technique. This is a very popular method of composite fabrication, limited

by its ability to produce simple shapes.

Initially, a plate consisting of epoxy resin with glass and hemp fiber reinforcement was

fabricated. The plate was made up of 55% fiber and 45% Resin by weight.

FABRICATION STEPS:

1) The bottom slab of the mould (granite slabs) is thoroughly cleaned with acetone andrelease film is spread on it.

2) Initially, a plate consisting of Epoxy resin with glass and hemp fiber reinforcement isfabricated. This plate consists of 55% glass and hemp fiber and 45% epoxy by

weight.

3) The initial material preparation includes getting the glass and hemp fabric cut to thedesired size.

4) The weight of fabrics is determined, in accordance with which the quantity of resinto be used is decided in such a way that the final plate is made up of 45% resin and

55% reinforcement by weight

5) The resin is taken in two separate bowls (because of the relatively short gelling timeof epoxy which was 20mins.), each bowl containing half the total weight.

6) The curing additives(hardener) are added in the specified proportions, stirredthoroughly and the first resin coat is applied on the release film as per the size of the

fabric.


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7) The first layer of fabric is carefully placed over the resin coat in and thoroughcompaction is achieved to prevent air bubble entrapment.

8) This is followed by the application of alternate layers of resin and reinforcement upto desired thickness is achieved. After the final resin coat is applied, the lay- up is

covered by another release film. The mould is closed by placing the top slab.

9) The top slab on account of its weight (18 kg) compresses the lay-up to the desiredthickness of 3.5mm, which is maintained using appropriate stoppers and the lay- up

is allowed to cure for 6-8 hours before it is retrieved from the mould.

10)The above steps are repeated to fabricate composite plates of different orientation.


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Granite Slabs forming the mold. Affixation of Release Film

Application of first resin coat. Placement of fabrics.

Placing release film over the lay-up Curing Stage


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DEPT OF MECHANICAL ENGG M TECH (MMD) N C E T

Reference

1. Knothe, J., Flster, Th., Naturfaserverstrkte Fahrzeugteile, Kunststoffe 87 (1997),Carl Hanser Verlag, Germany, pages 1148-1152

2. Amar, K.M., Manjusri, M. and Lawrence, T.D. 2005. Natural Fibers, Biopolymers,and Bio-composites. CRC Press, Tailor & Francis.

3. Maiti, S.N. and Singh, K. 1986. Influence of wood flour on the mechanical propertiesof polyethylene. J. Appl. Poym. Sci. 32:4285-4289.

4. Devi, L., Bhagawan, S. and Thomas, S. 1997. Mechanical properties of pineappleleaf fi ber-reinforced polyester composites. J. Appl. Polym. Sci. 64:1739-1748.

5. Chen, X., Gao, Q. and Mi, Y. 1998. Bamboo Fiber-reinforced polypropylenecomposites: a study of the mechanical properties. J. Appl. Polym. Sci. 69:1891-1899.

6. Thwe, M.M. and Liao, K. 2002. Effects of environmental aging on the mechanicalproperties of bamboo-glass fiber reinforced polymer matrix hybrid composites.

Composites Part A. 33:43-52.

7. Wambua, P., Ivens, U. and Verpoest, I. 2003. Natural fibers: can they replace glassin fi ber-reinforced plastics? Compos. Sci. Technol. 63:12591264.

8. Herrera-Franco, P.J. and Valadez-Gonzalez, A. 2005. A study of the mechanicalproperties of short natural-fiber reinforced composites. Composites B 36:597-608.

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