mechanical properties of composites using natural ...

MECHANICAL PROPERTIES OF COMPOSITES USING NATURAL RUBBER WITH EPOXY RESIN

A Thesis Submitted to the College of Engineering of Al-Nahrain University in Partial Fulfillment of the Requirements for the Degree of Master of Science in Mechanical Engineering

by NABEEL SHALLAL THAMER ALMURAMADY

(B.Sc., in Mechanical Engineering 1999)

Safar

1428

March

2007

‫الخواص الميكانيكية للمواد المركبة‬ ‫بأستخدام المطاط الطبيعي مع راتينج األيبوكسي‬

‫رسالة‬ ‫مقدمة إلى كلية الهندسة في جامعة النهرين‬ ‫وهي جزء من متطلبات نيل درجة ماجستيرعلوم‬ ‫في الهندسة الميكانيكية‬

‫من قبل‬ ‫نبيل شالل ثامر المرمضي‬ ‫(بكالوريوس في الهندسة الميكانيكية ‪)1999‬‬

‫صفر‬

‫‪1428‬‬

‫آذار‬

‫‪2007‬‬

Certification We certify that this thesis entitled “Mechanical Properties of Composites Using Natural Rubber With Epoxy Resin ” was prepared by Nabeel Shallal Thamer Al-Muramdy under our supervision at Nahrain University / College of Engineering in partial fulfillment of the requirements for the degree of Master of Science in Mechanical Engineering.

Signature:

Signature:

Name: Prof. Dr. Muhsin J. Jweeg

Name: Dr. Hani A. Ameen

(Supervisor) Date:

/

/ 2007

(Supervisor) Date:

/

/ 2007

Signature: Name: Prof. Dr. Muhsin J. Jweeg (Head of Department) Date:

/

/2007

Certificate We certify, as an examining committee, that we have read the thesis entitled “Mechanical Properties of Composites Using Natural Rubber With Epoxy Resin”, and examined the student Nabeel Shallal Thamer Al-Muramdy in its content and found it meets the standard of thesis for the Degree of Master of science in the Mechanical Engineering.

Signature:

Signature:

Name: Prof. Dr. Muhsin J. Jweeg

Name: Dr. Hani A. Ameen

(Supervisor) Date:

/

/2007

(Supervisor) Date:

/

/2007

Signature:

Signature:

Name: Asst.Prof. Dr. Samira K. Radhi

Name: Dr. Ali H. Mohammad Al Hilli

(Member) Date:

/

/2007

(Member) Date:

/

/2007

Signature: Name: Asst. Prof. Dr. Adnan N. Jameel (Chairman) Date:

/

/2007

Approval of the College of Engineering

Signature: Name: Prof. Dr. Muhsin J. Jweeg (Acting Dean) Date:

/

/ 2007

Abstract The mechanical properties of three types of natural rubber vulcanized, unvulcanized and reinforced rubber have been investigated in this research, every one of these types was in six percentages of epoxy (0%, 20%, 40%, 60%, 80% and 100%) specimen was made in the laboratories and devices of the public company of tires in Al-Dywania by using one of the tire dough called “Tread Dough”.

The value of Young’s modulus has maximum decreased in vulcanized rubber reach to 74.5% and maximum increase in unvulcanized and reinforced rubber reach to 317.5% and 23.6% respectively, yield stress, tensile strength and yield strain, also calculated for each case of these types and for all percentages of epoxy resin.

The values of resilience , work done , toughness and the percentages of reduction or increment and it was in vulcanized reduction between (6.5% to 56.7%) , in unvulcanized and reinforced rubber increment was between (68% to 89.4%) and ( 62.8% to 137.4% ) respectively, these values were calculated by using Simpson’s rules and MathCAD program.

Hardness, also studied in three types vulcanized, unvulcanized and reinforced rubber and also in the six percentages of epoxy resin in three types. It was found that the hardness is increased proportionally with increasing the percentage of epoxy resin, in vulcanized between (62% to 95%), in unvulcanized between (25% to 74%), in reinforced between (37% to 82%).

I

Special compression device was made according to the ASTM Standards to test the compression samples by using static compression method.

Compression set of experiments have been conducted to find the influence of adding the epoxy resin to the natural rubber, also to show the value of compression and that the compression is increased when increased the percentages of epoxy resin in the case of vulcanize rubber between (45% to 180%) , but in the case of unvulcanized rubber the compression is decreased when the percentage of epoxy resin increased between (200% to 110%).

Keyword: Mechanical Properties, Composites Material, Natural Rubber and Epoxy Resin

II

List of Contents Contents

Page

Abstract

I

List of Contents

III

Notations

VI

List of Tables

VIII

List of Figures

IX

Chapter One : Introduction 1.1 General

1

1.2 Matrix Materials

6

1.2.1 Thermoplastics

7

1.2.2 Thermosetting Resin

8

1.2.2.1 Epoxy Resin

8

1.3 Reinforcement Materials

9

1.4 Interface and Bounding in Composite

10

1.5 Classification of Composite Materials

11

1.5.1 Fibrous Composite

12

1.5.2 Composites Strengthened by Dispersion

12

Chapter Two : Literature Survey 2.1 Tensile Test

14

2.2 Rubber Filler Interaction

17

2.3 Rubber Crystallization

18

2.4 Rubber Molecular Orientation

19

2.5 Cord Rubber Composite

20

III

List of Contents (continued) Contents

Page

2.6 Epoxy Resin

21

2.7 Work Statement

22

Chapter Three : Theoretical Part 3.1 Particle Strengthening

23

3.2 Whisker Composite

25

3.3 Flake Composite

25

3.4 Bounds on the Modulus

26

3.5 Physical Properties

27

3.6 Mechanical Properties

28

3.7 Stress and Strain

28

3.8 Compressive Strength

30

Chapter Four : Experimental Part 4.1 Introduction

33

4.2 Manufacturing of Materials

33

4.2.1 Reinforcing Materials

36

4.2.2 Matrix Material

36

4.3 Materials Specimens Preparation

37

4.4 Moulds Preparation

39

4.4.1 Tensile Test Specimens

39

4.4.2 Compression Test Specimens

41

4.4.3 Hardness Test Specimens

42

IV

List of Contents (continued) Contents

Page

Chapter Five : Results and Discussion 5.1 Introduction

44

5.2 Tensile Test

44

5.2.1 Tensile Test for Standard Vulcanize Specimen

46

5.2.2 Tensile Test for Unvulcanize Specimen

48

5.2.3 Tensile Test for Reinforcement Specimen

50

5.3 Hardness Test

76

5.4 Compression Test

78

Chapter Six : Conclusions and Recommendations 6.1 Conclusions

80

6.2 Recommendations

81

References

82

V

Notations Symbol A C d

Definition Area

Unit m²

Compression set expressed as percentage of the original deflection

%

Diameter

m

Ec

Modulus of elasticity for composite

Pa

Ef

Modulus of elasticity for filler

Pa

Em

Modulus of elasticity for matrix

Pa

Force

N

∆G

Change in Gibbs Free Energy

J

∆H

Change in enthalpy

J

Length

m

mc

Mass of the composite

kg

mf

Mass of filler

kg

mm

Mass of matrix

kg

NR

Natural Rubber

-

SBR

Standard butyl rubber

-

F

l

∆S

Change in entropy

J/k

T

Absolute temperature

to

Original thickness of specimen

mm

ti

Finial thickness of specimen

mm

tn

thickness of spacer bar used

mm

νc

Volume fraction of composite

VI

k

-

Notations (continued) Symbol

Definition

Unit

νf

Volume fraction of filler

-

νm

Volume fraction of matrix

-

ρc

Density of composite

kg/m3

ρf

Density of filler

kg/m3

ρm

Density of matrix

kg/m3

σ

Stress

N/mm²

ε

Strain

-

VII

List of Tables Table

Title

Page

4-1

Contents of Dough

38

5-1

Determination of Tensile Values for Vulcanized Rubber

52

5-2

Determination of Tensile Values for Unvulcanized Rubber

53

5-3

Determination of Tensile Values for Reinforced Rubber

54

5-4

Values of the Hardness Test to the Vulcanized Rubber

76

5-5

Values of the Hardness Test to the Unvulcanized Rubber

77

5-6

Values of the Hardness Test to the Reinforced Rubber

77

5-7

Compression Set of Vulcanized Rubber Specimens

78

5-8

Compression Set of Unvulcanized Rubber Specimens

79

VIII

List of Figures Figure

Title

Page

1-1

Classification Scheme for the Various Composite types

1

1-2

Spherical reinforcing carbon black in the natural rubber

6

1-3

Structure of Verta resin

8

1-4

Curing mechanism of Epoxy resins

9

1-5

Different shapes of reinforcement used in composite

10

materials 1-6

Types of composite materials

11

1-7

Types of fiber reinforcement

12

3-1

Stress-strain curve

29

3-2

Stress-strain curve for different material

30

3-3

Stress- strain relation in compression for ductile and non-

32

ductile materials 4-1

Mixing Device of Natural Rubber

34

4-2

Rollers Machine

34

4-3

Failed samples

35

4-4

Tensile Test Specimens

40

4-5

Contents of Compression Device

41

4-6

Shore Durometer

42

4-7

Heated Presser Machine

43

5-1

Tensile Specimens

44

5-2

Computerized Test Meter

45

5-3

Tested Specimens

45

IX

List of Figures (continued) Figure 5-4

Title a-Stress–Strain for Standard 0% Epoxy Vulcanize Rubber

Page 55

b-Stress–Strain for Standard Vulcanize Rubber [50, 51] 5-5

Load – Extension Curve for Standard Vulcanize Rubber

55

5-6

Comparison Stress–Strain Curve for Standard Vulcanize

56

Rubber with 20% Epoxy 5-7

Comparison Load–Extension Curve for Standard Vulcanize

56



57



57



58



58



59



59



60


Comparison Load–Extension Curve for Standard Vulcanize Rubber with 100% Epoxy

X

60


Title

Page


61

Rubber with all Percentage of Epoxy 5-17


61


Stress-Strain Curve for Unvulcanize Rubber

62

5-19

Load – Extension Curve for Standard Unvulcanized Rubber

62

5-20

Comparison Stress–Strain Curve for Standard Unvulcanize

63


Comparison

Load–Extension

Curve

for

Standard

63


64

Unvulcanize Rubber with 20% Epoxy 5-22


Comparison

Load–Extension

Curve

for

Standard

64


65



Comparison

Load–Extension

Curve

for

Standard

65


66



Comparison

Load–Extension

Curve

for

Standard

66


67


Rubber with 100% Epoxy

XI


Title Comparison

Load–Extension

Page Curve

for

Standard

67

Comparison Stress–Strain Curve for Standard unvulcanize

68



Comparison

Load–Extension

Curve

for

Standard

68

Unvulcanize Rubber with all Percentage of Epoxy 5-32

Stress–Strain Curve for Standard Reinforced Rubber

69

5-33

Load – Extension Carve for Standard Reinforced Rubber

69

5-34

Comparison Stress–Strain Curve for Standard Reinforced

70


Comparison Load–Extension Curve for Standard Reinforced

70



71



71



72



72



73


Comparison Load–Extension Curve for Standard Reinforced Rubber with 80% Epoxy

XII

73


Title

Page


74



74



75


Comparison Load– Extension Curve for Standard Reinforced Rubber with all Percentage of Epoxy

XIII

75

Chapter One Introduction 1-1 General Many of modern technologies required materials with usual combinations of properties that can not be met by the conventional metal alloys, ceramics, and polymeric materials. Material property combinations and ranges have been, and are yet being, extended by the development of composite materials [1]. The word composite in the composite material signifies that two or more materials are combined on a macroscopic scale to form a useful material. There are three commonly accepted types of composite materials as shown in Fig.1-1 1. Fibrous composites which consist of fibers in a matrix. 2. Laminated composites which consist of layers of various materials. 3. Particulate composites which composed of particles in a matrix. Composite

Particlereinforced

LargeParticle

Dispersion Strengthened

Fiberreinforced

Continuous (Aligned)

Discontinuous (Short)

Randomly oriented

Structural

Laminates

Sandwich Panels

Aligned

Figure 1-1 Classification Scheme for the Various Composite Types

1

Particulate composites consist of particles of one or more materials suspended in a matrix of another material. The particles can be either metallic or nonmetallic as can the matrix.

The most common example of a nonmetallic particle system in a nonmetallic matrix (the most common composite material) is rubber. Rubber is particles of carbon, sulfur and another material that are bound together by a mixture of natural rubber that has chemically reacted and hardened. The strength of the rubber is normally ascribable to the black carbon.

Composite materials are used increasingly in the many military and civil applications due to their excellent mechanical properties like high specific strength, specific stiffness, and resistance to corrosion, increased fatigue life among others. However, one of the main concerns in the use of advanced composite is their poor translaminar properties, which become critical under situations like tensile and impact loading [2].

The modern plastics industry began with the utilization of natural rubber for erasers and in rubberized fabrics a few years before Goodyear's discovery of vulcanization in 1835. In the next decade the rubber industry a rose both in England and in the United State. In 1851 hard rubber, or ebonite, was patented and commercialized. Rubber like elasticity is in many respects a unique phenomenon, involving properties markedly different from those of low- molecular- weight solids, liquids or gases. The properties of typical elastomers are defined by the following requirements [3]:

2

a. They must stretch rapidly and considerably under tension, reaching high elongations (500-1000%) with low damping, little loss of energy as heat. b. They must exhibit high tensile strength and high modulus (stiffness) when fully stretched. c. They must retract rapidly, exhibiting the phenomenon of snap or rebound. d. They must recover their original dimensions fully on the release of stress, exhibiting the phenomenon of resilience and low permanent set.

Although the thermodynamics associated with rubber elasticity was developed in the middle of the nineteenth century, the molecular requirements for the exhibition of rubber behavior were not recognized until 1932. Theories of the mechanism relating these molecular structure requirements phenomena of rubber elasticity were developed soon after. The molecular requirements of elastomers may be summarized as follows [3]: a. The material must be a high polymer. b. It must be above its glass transition temperature Tg to obtain high local segment mobility. c. It must be amorphous in its stable (unstressed) state for the same reason. d. It must contain a network of crosslink's to restrain gross mobility of its chains.

Epoxy resins are basically thermosetting resins , epoxy resin have gained wide acceptance in the industrial field in the past 20 years in adhesives, coatings, potting, building construction, chemical-resistant equipment, boats, etc. the properties that have made the epoxies popular in so

3

many fields are their versatility, excellent adhesion, low cure shrinkage, good electrical properties, compatibility with a great number of materials, resistance to chemical and weathering, dependability, and ability to cure under adverse conditions[3]. Epoxies can be compounded to produce a wide range of handling, curing and final part properties by choice of the basic resin (s), curing agent(s) filler(s), and modifier(s). As the curing agent becomes an integral part of the cured compound, its choice is a controlling influence on the curing and final properties of the mixture. Fillers and modifiers are used to tailor the liquid viscosity and cured properties to the applications. A variety of polymers can be blended and corrected with epoxy resins to provide certain desired properties; the most common of these are rubber, phenolic, nylon, and polysulfide resins. The epoxy resins are cured by many types of materials, including polyamines, polyamindes, polysulfides, urea- and phenol- formaledlhyde, and acids or acid anhydrides, through coupling or condensation reactions.

The epoxy resin can be used in both molding and laminated techniques to make articles with better mechanical strength, chemical resistance and electrical insulating properties [3].

Generally, composite material can be defined as a material consisting of two or more physically and/or chemically distinct phases suitably arranged or distributed. A composite material usually has characteristics that are not depicted by any of its components in isolation.

4

The continuous phase is referred to as the matrix, while the distributed phase is called the reinforcement. Characteristics of a composite depend on three things [4]. 1- Matrix Material. 2- Reinforcement Material. 3- Interface and Bonding.

In principle, any two materials could be combined to make a composite and might be mixed in any geometry. Both elastomers and plastics are frequently reinforced with the various particulate materials. Many of the modern rubbers would be severely restricted without reinforcing particulate materials such as carbon black and epoxy resin. Carbon black consists of very small and essentially spherical particles of carbon, produced by combustion of natural gas or oil in an atmosphere that has limited of air supply, when added to vulcanized rubber , this extremely inexpensive material enhances tensile strength , toughness , tear and abrasion resistance. Automobile tiers contain on the order of 15 to 30 vol% of carbon black. The carbon black a provide significant reinforcement, the particle size must be extremely small, with the diameters between 20 to 50 nm; also, the particles must be evenly distributed throughout the rubber and must form a strong adhesive bond with the rubber matrix Particle reinforcement using other materials (e.g. silica) is much less effective because this special interaction between the rubber molecules and particle surfaces does not exist. Fig. 1-2 is an electron micrograph of a carbon black – reinforced rubber.

5

Natural rubber

Carbon particle

Figure 1-2 Spherical reinforcing carbon black in the natural rubber [1]

1-2 Matrix material Matrix materials utilized in most commercial composite can be divided into four general categories [5, 6]. 1- Polymeric, which includes a number of thermosetting and thermoplastic resins. 2- Metallic, consisting of pure metals and alloys. 3- Ceramic matrix material. 4- Carbon and graphic matrix materials. The function of the matrix in a composite material is usually multifold. Matrices are designed to protect the reinforcing phase from structural damage, corrosive attack and reactions that would degrade the reinforcement properties. The matrix phase also serves to transmit applied stresses to the reinforcing constituents. The matrix may be selected for its physical properties, such as density thermal and electrical conductivity (or electrical receptivity), thermal expansively, melting or softening temperature and translucency [6].

6

1-2-1 Thermoplastics In general, the properties of thermoplastic polymers can be changed by changing the length of individual chains, changing the form of the individual chains, e.g. putting branches on the chain of ‘lumpy molecular’, changing the strength of bonds within chains and changing the strength between chains.

Crystalline is influenced by the nature of the molecular chains. Crystalline increases the melt temperature and reducing transparency of the unfilled plastics where the crystals in the material scattering the light [7]. The use of engineering thermoplastics as matrices originated with a view to realize low cost manufacturing. Factors contributed to this objective are [5]: 1- Long prepreg stability without the need for refrigeration. 2- Fast processing cycle. 3- Ease of quality control. 4- Ability to reprocess the components to remove imperfections. 5- High damage tolerance characteristics.

Thermoplastics are useful as composite matrices are either crystalline or amorphous. This affects their relative resistance to solvents and chemicals. Matrix resins of polymer may be classified into the following categories [5]. 1- Polyaryl, Ethers. 2- Imides and Amide-imides. 3- Polyarylene sulfides.

7

1-2-2 Thermosetting Resins Thermosetting polymers are stronger and stiffer than thermoplastics and generally can be used at higher temperature. As they cannot be shaped after the initial reaction in which the polymer chains are formed [5]. In general, thermosets have high thermal stability, high dimensional stability, high stiffness, good resistance to creep, has a low densities, and high electrical and thermal insulation properties [7] The most common resins of this type are epoxies, phenolics, polyamides and cyanate esters [5].

1-2-2-1 Epoxy Resin: General Chemistry and Description The most common epoxy resins are glycidyl ethers of alcohols or phenolics. Liquid epoxy resin is the diglycidyl ether of bisphenol A (DGEBA) and represents greater than 75% of the resin used in industrial applications. Structure of Verta resin shown in Fig. 1–3

Figure 1–3 Structure of Verta resin [8]. This resin has the consistency of honey. The epoxide group on the end of these molecules serves as the reactive site for crosslinking in these thermoset polymers.

The chemical chosen to react with these epoxides is

referred to as the curing agent, and it typically has active hydrogen attached to nitrogen, oxygen, or sulfur. Amine curing agents are the most common and can be primary or secondary, aliphatic or aromatic, or cycloaliphatic.

The

amines typically have greater than three reactive sites per molecule that

8

facilitate the formation of a three-dimensional polymer network when mixed with the epoxy resin Fig. 1-4.

Figure 1-4 Curing mechanism of Epoxy resins While the reaction of amines and epoxides occur at room temperature and below, care must be taken in the selection of the curing agent to insure that a complete reaction takes place. Amines designed for room temperature applications typically employ plasticizers to insure complete reaction. Amines designed for heat-cured reactions use little or no plasticizers and typically give thermoset with higher strength and thermal performance.

1-3 Reinforcement Materials Reinforcements for composites can be fibers, particles or whiskers. Fibers are essentially characterized by one very long axis with other two axes either often circular or near circular. Particles have no preferred orientation and so does their shape. Whiskers have a preferred shape but are small both in diameter and length as compared to fibers. Figure 1-5. Shows types of reinforcement materials. Reinforcing constituents in composites, as the word indicates, provide the strength that makes the composite what it is. But also serves certain additional purposes of heat resistance or conduction, resistance to corrosion and provide rigidity [5].

9

Reinforcement can be made to perform all or one of these functions as per the requirement. Reinforcement that embellishes the matrix strength must be stronger and stiffer than the matrix and capable changing failure mechanism to the advantage of the composite. This means that the ductile should be minimum or even nil and the composite must behave as brittle as possible.

Whiskers Flake

Particle

Fiber

Filler Lamina

Figure 1-5 The different shapes of reinforcement used in composite materials. [9]

1-4 Interfaces and Bonding in Composites The interface region in a particular composite has a great deal in determining the ultimate properties of the composite, essentially for two reasons: -

10

The interface occupies a very large area per unit volume in a composite, and in general the reinforcement and the matrix form a system that is not in thermodynamic equilibrium. The interface may be defined as a boundary surface between two phases in which a discontinuity in one or more material parameters occurs. An important parameter in regard to the interface is the wettability of reinforcement by the matrix. Wettability refers to the ability of a liquid to spread on a solid substrate.

Good wetting is a necessary, but not sufficient

condition for strong bounding, the other important factors such as chemical, mechanical, thermal and structural factors, affect the nature of the bounding between reinforcement and matrix materials[4].

1-5 Classification of Composite Materials Composites can be classified on the basis of the type of reinforcement as shown in Fig.1– 6 [5]

Fiber – reinforced composite

Particulate composite

Laminar composite

Filled composite

Flake composite

Figure 1-6. Types of composite materials. [9] 11

1-5-1 Fibrous Composite The main functions of the fibers in a composite are to carry most of the load applied to the composite and provide stiffness. For the reason, fiber materials have high elastic modulus. The fibers used may be continuous or discontinuous and may be aligned so that they are all lying in the same direction or randomly oriented as shown in Fig 1-7. Aligning them all in the same direction gives directionality to the properties of the composite. [7]

a- Continuous, aligned

b- Discontinuous,

c- Discontinuous, d

Figure 1-7 Types of fiber reinforcement [9]

1-5-2 Composites Strengthened by Dispersion In dispersion strengthened composites, small particles dispersed in a matrix, therefore; slip and dislocation movement accompanies the deformation in the matrix, the degree of strengthening achieved is proportional to the ability of the particles to impede the dislocation movement. It follows that a finer dispersion of particles results in greater strengthening. The objective is to have the particles small enough and spaced

12

closely enough so that dislocation movements cannot easily occur between them [10]. It can be shown that in dispersion strengthening with particle diameter less than 0.1µm, volume fraction1-15% and matrix means free path (0.01 to 0.03µm), dislocation movement can be effectively impeded [6,10]. The strengthened matrix becomes the main load –bearing constituent and the mechanical properties of the dispersion-strengthened composite is isotropic because of dispersion particles in all directions of the matrix material.

13

Chapter Two Literature Survey 2.1 Tensile Test The first simple analysis process of tensile stresses distribution along the fibers of a composite material has been accomplished by the researcher Cox, where as the general analysis, similar to Cox's analysis, was achieved by the two researchers Hollister and Thomas, in 1966[11]. Garg et al in 1973 [12] studied the longitudinal tensile strength in the fibrous composite and laminated materials. B.D.Agawal and J.N.Narang, in 1977 [13] studied the behavior of some glass fibers samples, reinforced by epoxy resin with different fibers directions in impact and tensile tests. Tensile tests yielded the information necessary for studying stress- strain behavior that is dependent on the angular direction of fibers, and stiffness of composite. L.L. Clements and R.L. Moore, in 1978 [14] explained practically the composite properties of e-glass fiber with various volume fractions. While the scientist, D.Hull, in 1981 [15] studied the mechanical behavior of laminates reinforced with unidirectional fibers being pulled in the fibers direction until they reach failure. The researcher H.M. Lahiff, in 1986 [16] investigated the mechanical properties of the two types of epoxy resins that are DGEBA (MY750 and GY255 Ciba Geigy) with glass fibers. At various temperature levels, he studied the effect of temperature degrees on young modulus and tensile strength.

14

Guild et al, in 1988 [10] presented a predictive model of mechanical behavior of continues longitudinal fiber composite. This model used a combination of the finite element analysis and spatial statistical technique. P.C.Powell, in 1992 [18] performed many studies and determined the mechanical properties of different layers as well as the longitudinal tensile strength of lamina. Minguet et al, in 1994 [19] made various test methods commonly used for measuring mechanical behavior of composite, and the evaluated these methods to determine their suitable for textile composite. Three different types of textile composites were analyzed experimentally and theoretically. S. D. Salman, in 2002 [20] studied four groups of composite materials are experimentally studied. The first consists of unidirectional angle-ply fibers in an epoxy resin matrix with 2, 4, 6, 8, 10, 12, and 14 layers. The second group is of the mate type with 1, 2, 3, 4, 5, 6 and 7 layers. Both groups are of a volume fraction of 35% and a real weight of 300 g/m². The third and fourth groups are similar to the first and second respectively but with a volume fraction of 50% and a real weight of 600 g/m². The tensile test show that the mat type composite material exhibit higher fracture load but at lower stiffness. Both unidirectional and mat type's tensile properties become close to each other with increased number of layers. Both types exhibit multi-failure pattern specially at low number of layer. Al – Zangna, in 2002[21] studied the effect of adding the Iraqi ceramic raw materials (Bauxite + Kaolin) on the mechanical properties of polymer concerning the parameters. The polymer matrix particulate has been prepared by adding the ceramic powder (Bauxite + Kaolin) to the epoxy of type (CY223) as an example to the thermosetting polymer. The experimental results have been obtained and concluded that the best particle size is smaller than (10µm); the best weight fraction is (35%).

15

A. Jowdat, in 2005 [22] studied the influence of copper powder as reinforcement to a thermosetting epoxy resin matrix. The mechanical properties included the Tensile strength, Compression strength. The composite material parameters included the weight fraction and particle size of the reinforcement. The moduli of elasticity and yield strength have shown an increase in their value with an increase in weight fraction of the particle Husam A. Kareem, in 2002 [23] studied the influence of nickel powder as reinforcement to a thermosetting epoxy resin matrix. The mechanical properties included the Tensile strength, Compression strength and Hardness. The composite material parameters included the volume fraction and particle size of the reinforcement.

The volume fraction ranged

from zero, epoxy resin on its own up to 15% volume fraction reinforcement Mawloud. H. Al-Dulaimi, in 2006 [24] studied the influence of Aluminium powder and Aluminium with Titanium powder as reinforcement to a thermosetting epoxy resin matrix. The mechanical properties included the Tensile strength, Compression strength, bending and fatigue stress. The composite material parameters included the weight fraction and particle size of the reinforcement. (The particle size for the Aluminium powder is less than or equals to 29µm (d≤29) and the weight fraction has different values equals to 10%, 20% and 30%) and Aluminium with Titanium powder (for Aluminium the particle size is 29µm (d≤29) and the weight fraction has different values equals to 10%, 20% and 30%) and for Titanium the particle is 24µm (d≤24) and the weight fraction is equal to 1% for each different weight fractions of Aluminium powder ) to epoxy resin. the experimental results obtained from experiments have been analyzed in order to achieve the best result. It is concluded that the Young's modulus and modulus of rigidity increase when the weight fraction for Aluminium and Aluminium with Titanium powder increase.

16

2.2 Rubber Filler Interaction The interaction between the rubber and the filler has been studied to determine the effects on failure of the compounds [25, 26]. Neogi et al., in 1989 [25] have researched the high temperature interaction between rubber and filler by using the strain amplification factor. When carbon black is added as reinforcement, the degrees of freedom of the rubber chains are decreased due to the interaction and adsorption of no deformable carbon black onto the rubber. Upon an applied load the rubber must bear the total strain; however, the local strain within the rubber phase is greater than the global strain attained by the system. This difference between the local and the global strains is termed as the strain amplification factor. Chung et al., in 1991 [27] investigated the effects of carbon black on the ultimate properties of an elastomers. They examined the critical tearing energy as well as a critical J-integral. They found that for Natural Rubber compounds, crystallization could be observed near the crack tip. Crystallization hindered the crack propagation through the thickness of the specimen. The level of carbon black loading moderately affected the To of the NR compounds, with the value ranging from 4.1 kN /m to 6.9 kN /m. The true modulus of the compound was found to increase with increasing levels of carbon black. Wang, in 1998 [28] found that the modulus of the compound increased with the increasing level of carbon black. The increase was consistent for both the loss modulus as well as the storage modulus. Ascribed the stiffening due to the filler by the adsorption of polymer molecular chains on the filler surface. This adsorption reduces the mobility of the polymer segments and results in a rubber shell on the filler surface. The reduced mobility and the rubber shell increase the polymer viscosity. This increase in viscosity created

17

a broadening of the spectrum of relaxation times, τi, and the modulus accordingly increases. Lake and Lindley, in 1964 [26] investigated the effect of carbon black on the fatigue life of rubbers. They found that the addition of carbon black serves as a source for hystersis in the compound. This added carbon black considerably reduced the temperature dependence of fatigue life of SBR but did not influence the fatigue life of natural rubber.

2.3 Rubber Crystallization Rubber crystallization occurs due to a decrease in the localized entropy upon an imposed deformation [29, 32]. This phenomenon is explained by the Gibbs free energy. The thermodynamic formula, the Gibbs free energy, is shown as follows ∆G = ∆ H − T ∆S

... (2-1)

Where ∆G is the change in the Gibbs free energy, ∆H is the change in the enthalpy, T is the absolute temperature and ∆S is the change in the entropy of the system. Allegra, in 1985 and 1987 [31, 32] has found that the crystallization of rubber can be modeled as a third order transition. This is different than the second order theory of Flory, in 1947 [33]. Goritz et al., in 1985 [30] discussed an additional Process of straininduced crystallization. If a maximum in the degree of crystallinity in not reached under the applied load, then the remainders of the crystallizable chains crystallize on reducing the temperature. He investigated both of the two strain-induced crystallization phenomena by performing differential scanning calorimetry scans on deformed specimens. For a cis-1,4 polybutadiene specimen extended to 400 % strain the two crystalline melting

18

regions appeared separately. The full width half maximum, of the temperature induced crystalline region was 267 k while the full width half maximum of the strain induced crystalline region was 310k.The full width half maximum of the temperature induced crystallization between strained sample and an unstrained sample differed by 5 k. Goritz et al. [30] explained this difference as a stress induced entropic effect. Crystallization in NR is a stress induced an entropic effect. The reduction in the entropy can occur in the regions of high stress concentrations such as the tip of a crack. The interaction between rubber and filler can affect the mechanical properties of NR, but what effects are there to the compound as a function of time.

2.4 Rubber Molecular Orientation Dubault A., in 1985 [35] and Xingfa M, in 1985 [39] studied the molecular orientation of rubber is typically investigated in terms of an applied load and the resulting strain induced crystallization. Mitchell G.R, in 1984 and 1985 [34, 36] and Udagawa Y., in 1985 [37] Techniques such as wide angle x-ray scattering, deuterium magnetic resonance [35], stationary fluorescence polarization [38] have been applied to determine the orientation parameters of the network. However, when studying polymers one must always keep in mind the history of the specimen prior to testing. Fleischman T., in 1985 [40] explained the theory of rubber elasticity is based upon an irregular, three-dimensional network; it does not take into account any history effects. At room temperature there is no physical aging of a NR vulcanizate, because Tg ≈ -75ºC, but there is a mechanical history to the specimen. During vulcanization, a rubber compound changes from a

19

relatively weak viscoelastic liquid to a relatively strong viscoelastic solid. In order for a sheet of vulcanized rubber to be formed it is typically milled down to the desired testing thickness. After milling the sheet is place in a hot press where it is cured at elevated temperature and high pressure. Thus prior to the final vulcanized shape the sample has obtained a milling history that can orient the liquid polymer chains in a preferred direction.

2.5 Cord Rubber Composites The cord-rubber composite is a common laboratory specimen because it resembles the structural belts of a tire as well as conveyer belts and other systems [40]. Cord-rubber composites have been investigated in order to determine their crack initiation and propagation mechanisms [41, 45]. Using a model cord-rubber composite with exposed cords, Breidenbach et al., in 1979 [41] examined the mechanics of propagation of interply cracks. They assumed that the initiation process during which an interply crack was formed which is relatively short and excluded the process from their study. In their work they classified the specimens into three deformation regions: a central region where deformations are relatively uniform and approximately obey a pantographing model, and two regions along the free edge where deformations vary in a complex manner. In the edge regions shear strains up to 1000% can occur from an overall extension of up to 5%. These high shear strains create stress concentrations at the edge and lead to the initiation of penny shaped cracks at the cord ends. These penny shaped cracks coalescence to form a line crack parallel to the direction of loading which in turn develops into an interply crack. The interply crack propagates with the crack growth characteristics of

20

the material until delamination is extensive enough to exceed the load bearing capability of the laminate to the point of failure. Gent et al. in 1981 [42] assumed that the energy necessary to create a penny shaped crack needed to be greater than the sum of the energy required to fracture the cord-rubber interface and any increase in the strain energy of the rubber itself. Deformation in the cord was assumed to be negligible. Huang et al., in 1988 [43], Knowing that the two plies in a cord-rubber composite are rarely identical, demonstrated that cracks typically developed from the narrower ply. They also showed that the fatigue life of the composite was a linearly decreasing function with increasing dynamic amplitude; load and maximum Interlaminar shear strain. Lee B.L., in 1994 [44] and Martin R.H., in 2000 [45] show that the additional research into cord-rubber composites has focused on finite element modeling of the structure to determine areas of high stress concentration and to model the three-dimensional dynamic response of the composite.

2.6 Epoxy Resin Reinhart, in 1987 [46] demonstrated that the epoxy resins are usual extensively in the composite materials for a variety of demanding structural requirements. All epoxy resins contain the epoxide

Where R represents the point of attachment to the reminder of the resin molecule. Where the type of epoxy used in Reinhart work is epoxy laida Several researchers used epoxy resin to consist the composite materials like Ali H. Hilli [2] used of woven laminate composite material .three types of fibers were used which were E-Glass , carbon and Kevlar fiber with different types of weave styles. The matrices used were epoxy resin to form

21

the composite material. In this research the natural rubber with epoxy resin was used to form the composite material.

2.7 Statement of Work From the previous discussions, it is clear that there are many literatures dealing with the composite materials, but limited literatures investigated the rubber technology, therefore, this research will be concentrated on this subject, using composite materials of rubber and epoxy resin. Then this research investigates the effect of adding the epoxy resins upon the mechanical properties of natural rubber. The tensile test for three cases (vulcanized, unvulcanized and reinforced rubber) will be carried out in order to investigate the mechanical properties of the composite material; also the hardness and compression tests are investigated.

22

Chapter Three Theoretical Part 3-1 Particle Strengthening The particle strengthening of composite is similar to the dispersion strengthening but it differs in that particle size is larger and volume fraction is greater where the particle diameter is larger than 1µm and volume fraction is greater than 25% and the matrix means free path which is greater than 1µm. In particle strengthening, the load is shared by both the matrix and the particles where the particle initially impedes deformation of the matrix. [6, 21]. Generally, the properties of particle strengthening also depends on the form, size, direction of particle distribution in the matrix and the bonding between the particles and the matrix, also the interface in composite has a great influences to the properties of composite material. The particle and the matrix of composite material each one is either to be metals, ceramics and polymers as epoxy and polyester.

Many researchers make studies about this type of reinforcement and all of them agreed about these methods to calculate the modules of elasticity and rigidity [23].

1- The particles randomly distributed in the matrix. 2- The particles at the same size. 3- The particles bonded with the matrix strongly. 4- Each of the particles and the matrix isotropic.

23

The law of mixture [7, 21]: The mass (m c ) of composite is made up of the masses of the matrix (m m ) and the filler particle (m f ), mc = mm + m f

... (3.1)

Since the mass is volume time’s density then equation (3-1) can be written as below: vc ρ c = v m ρ m + v f ρ f

... (3.2)

And so: -

ρc =

vf vm ρm + ρf vc vc

… (3.3)

( v m vc ) is the volume fraction (V m ) that is matrix and ( v f v c ) is the volume fraction (V f ) that is filler particle. ρ c = Vm ρ m + V f ρ f

… (3.4)

Note that since v m = vc − v f , it must have: Vm = 1 − V f

… (3.5)

By substituting equation (3-5) in equation (3-4), will get ρ c = ρ m (1 − V f ) + ρ f V f = ρ m + V f ( ρ f − ρ m )

… (3.6)

Also the mass of the matrix and the mass of reinforcement material can be calculated as follows: Since,

V

then,

Vf =

f

=

v

f

vc

mf ρ f

… (3.7)

vc

Then,

m f = vcV f ρ f

… (3.8)

And,

m m = vc ρ m (1 − V f )

… (3.9)

24

3-2 Whiskers Composite Whiskers are single crystals grown with nearly zero defects, they are usually discontinuous and short fibers of different cross sections made from several materials like graphite, silicon carbide, copper, iron etc. Typical lengths are 3 to 55nm range. Whiskers differ from particles in that; whiskers have a definite length to width ratio greater than one. Early research has shown that whisker strength varies inversely with effective diameter. When whiskers were embedded in matrices, whiskers of diameter up to 2 to 10 µm yielded fairly good composites [5]. Herring and Glat discover whiskers at 1952. Also they discovered in Bell telephone laboratories that tensile strength of Tin whiskers greater than that of tin plate. At the same time other studies show that whiskers reinforced composites have a tensile strength equal to 0.1 of their modulus of elasticity. Finally, whiskers composite used in a great range of manufacturing like the manufacture of motorcar body panels [21]

3-3 Flake Composite Flake is small and very thin plates with two small dimensions have a 3 range of size (0.01-0.1) mm and thickness (0.001-0.005) mm. Manufacturing

of flake probably easy but it’s difficult to get the required size and shape, The degree of reinforcement directed proportional to the aspect ratio and the bonding forces between flakes and the matrix therefore the aspect ratio and bonding forces have a great deal about the spread of stress between material matrix and flakes also it prevents pull out and depends of flakes [21] Flakes have various advantages in structural applications. Parallel flakes filled composites provide uniform mechanical properties in the same plane as the flakes. Flake composite have a higher theoretical modulus of elasticity with cheaper production and can be handled in small quantities [5].

25

Finally, flake composite used for manufacturing exhaust nuzzle. [21]

3.4 Bounds on the Modulus The simplest cases have two bounds for predicting the tensile modulus. The upper bound is: Ec = (1 − V f )Em + V f E f

… (3.10)

This assumes equal strains in the two phases under elastic deformation. This equation contains only the composition variable and is often called the mixture rule and is known as the series model [1]. If the stresses of the two phases are assumed equal, the lower bound of the modulus is governed by the parallel mode. ⎛1−V f V f ⎞ ⎟ Ec = ⎜ + ⎜ E ⎟ E f ⎠ ⎝ m

−1

… (3.11)

Equations (3-10) and (3-11) have been applied to various physical properties e.g. the coefficient of thermal expansion, thermal conductivity and shear and bulk module.

Haplin-Tsai Equation This is a simple empirical expression reduced from Herman’s solution containing a geometric fitting parameter A, obtained by fitting with numerical solutions of formal elasticity theory composite moduli are put in the form, 1 + ABV f Ec = Em 1 − BV f

… (3.12)

Where: B = (E f Em − 1) (E f Em + A)

And A = 2 l d for tensile modulus. The ratio l d is the aspect ratio [1].

26

B-Paul Equation B-Paul equation has developed by assuming a good adhesion between the particles and matrix with a great influence. The tensile modulus of elasticity of the composite E c is given by: ⎡ 1 + (m − 1)V f2 3 ⎤ Ec = ⎢ ⎥ 23 ⎣⎢1 + (m − 1) V f − V f ⎥⎦

(

m =

Where: -

E

)

… (3.13)

f

Em

O. Ishai and L. J. Cohen Equation Ishai and Cohen equation depends on Paul equation by assuming the producing strain due to applied stress at composite material be constant so the composite moduli developed as below: ⎡ Vf m Ec = Em ⎢1 + ⎢⎣ (m − 1) − V f

⎤ ⎥ ⎥⎦

… (3.14)

Generally, the difference in theoretical and practical results belongs to that filled system depends not only on the material properties of the two components and the volume fraction but also on the size, shape orientation and the state of adhesion between the filler and the matrix [1].

3-5 Physical Properties Physical properties can be considered to include density and melting point [7]. They have a great influence for the natural properties of polymers as transparency, strength and elasticity. Studying of physical properties help to reduce disadvantages of polymers by chemical and technical processes like increasing thermal resistance and glass transition temperature [47]. These properties include strength, toughness and wear resistance. 27

3-6 Mechanical Properties Mechanical properties are important considerations in design of a structure or a machine, which enables the design to serve its function safely and well. Mechanical properties are usually expressed in terms of quantities that are primarily functions of stress or strain, but they are occasionally expressed in terms of other quantities such as time and temperature [8]. These properties include strength, stiffness, hardness, ductility, and toughness.

3-7 Stress and Strain When a material is subjected to external forces that make it extend or contract, then it is said to be in tension or compression, and in same situations can be subjected to both tension and compression e.g. a beam that is being bent. The stress being defined as [48]: -

Stress (Pa) =

Force ( N )

… (3.15)

Area ( m 2 )

When a material is subjected to tensile or compressive forces, it changes in length. The term strain is being used for the fractional change in length. Strain=

Change in length Original length

… (3.16)

Since strain is ratio of two lengths which has no units.

28

Figure 3-1 shows the stress-strain curve. Initially the graph is straight line and the material obeys Hooke’s law. The point at which the straight-line behavior is not followed is called the limit proportionality. With low stress the material springs back completely to its original shape when the stresses are removed, the material being said to be elastic. At higher forces this does not occur and the material is then said to show some plastic behavior. The term plastic is used for that part of the behavior, which results in permanent deformation.

This point often coincides with the point on a

stress-strain graph at which the graph stops being a straight line, i.e. the limit of proportionality.

The term tensile strength is used for the maximum value of the stress that the material can withstand without breaking, the compressive strength being the maximum compressive stress the material can withstand without becoming crushing. Fig.3-2 shows the difference in stress-strain curve for brittle, ductile and electrometric materials.

Stress

Limit proportionality Tensile strength

Yield point

Strain

Figure 3-1 Stress-strain curve [7]

29

Stress

Brittle

Ductile

Ductile(Necking) Elastomeric (Rubbery) Strain

Figure 3-2. Stress-strain curve for different material [21]

3-8 Compressive Strength The compressive strength is the maximum compressive stress that a material is capable of developing with a (brittle) material that fails in compression by rupturing; the compressive strength has a definite value. In the case of ductile, malleable, or semi viscous materials (Which do not fail in compression be a shattering fracture), the value obtained for compression strength is an arbitrary value dependent on the degree of distortion that is regarded as effective failure of the material. Fig.3-3. illustrates characteristic stress-strain diagrams for ductile and non-ductile materials in compression, the dashed line again showing the true stress- conventional strain relation; in compression it is lower than the conventional stress- strain diagram owning to the increase in cross section of the specimen while under compression loading [47].

30

Can be calculating the compressive strength by using these equations [48]: -

F A

σ =

… (3.17)

And can be calculated the true stress and strain by using the following equations.

ε = ln (1 + e ) V = Ao L o = AL → A = e=

… (3.18) Ao L o L

… (3.19)

⎞ ∆L L − Lo ⎛ L = = ⎜⎜ − 1⎟⎟ Lo Lo ⎠ ⎝ L0

… (3.20)

σ t = σ (1 + e )

… (3.21)

In the case of the elastomers the compressive strength can be calculated by using the equation (3.22). [49]:

C =

[(t o

− t i ) (t o − t n )]× 100

… (3.22)

Where: C = compression set expressed as percentage of the original deflection. to = original thickness of specimen. ti = final thickness of specimen. tn = thickness of spacer bar used.

31

Stress

Non ductile Ductile

Strain

Figure 3-3 Stress- strain relation in compression for ductile and nonductile materials [47]

32

Chapter Four Experimental Part 4.1 Introduction This chapter includes the experimental part that explains the types of materials (matrix and reinforcement materials) that are used to make samples for tests and the standard dimensions of each sample are shown in the photographs.

4.2 Manufacturing of Materials In this project Natural Rubber was used as the matrix material and (epoxy resin) and (carbon black powder) as the reinforcement material, three ways are used for manufacturing the samples, the first and second ways were failed and the third one was passed. The first way was by mix the natural rubber with epoxy resin only without any adding materials by special mixer shown in Fig.4-1 the result from this process was inhomogeneous and disintegrated material then the rubber was completely disintegrated and nothing obtained from this way. The second way was to treat the natural rubber alone in the mixer and then pass through rolling process in the special rolling machine shown in the Fig.4-2 to obtain a layer of natural rubber in thickness about ( 1mm ), then manufacturing the specimen by layers after coating by epoxy layers, the sample was formed of three layers of natural rubber and two layers of epoxy resin, this way also failed because the layers of natural rubber appeared tearing , inhomogeneous and filled by holes and cavities as shown in Fig.4-3.

33

Figure 4-1 Mixing Device of Natural Rubber

Figure 4-2 Rollers Machine

34

a

a- Samples by layers without reinforcement

b- Samples by layers with reinforcement Figure 4-3 Failed Samples

35

The third method to produce the specimens will be explained in the next article.

4.2.1 Reinforcing Materials Epoxy resins form thermosetting materials and are being combined with a hardener, which enables cross- links to be established between the epoxy molecules and to produce a thermoset material. The epoxy that was used for this work is type VERTA that is produced by VERTA COMPANY-TURKEY and it consists from two components of a high grade, low viscosity, colorless materials, and the density at 23˚C is approximately 1.05gr/cm 3 and has a mixing ratio of 2:1 based on weight, and on application time of 30 min at approximately 23˚C and after the solidification process, it demonstrates low density and high electrical resistance. Carbon Black powder that was used with small particle size which diameter 33 nm.

4.2.2 Matrix material The matrix material used natural rubber which prepared previously by special mixer as shown in Fig. 4-2 and added some of agent's materials in the limited percentages according to standard reference Maurice Morton, in 1973 [51] as follow:-

Dutrex oil Small amount may be added to control and standardize the viscosity of the individuals' batches.

Stearic acid A small amount of Stearic acid has long been standard addition to natural rubber mixes to assist the action of accelerators and serves similar

36

purpose in most sulphur vulcanizable rubber, it is also aide processing by exerting a plasticizing action and reducing the tendency.

OBTS, NOX, IPPV (Vulcanize Agents) in combination with vulcanizing agents, these materials reduce the vulcanize time (cure time) by increasing the rate of the vulcanization in most cases; the physical properties of the products are also improved.

Sulphur (Vulcanize Agent) these materials are necessary for vulcanization since without, the chemical crosslinking reactions involving these agents, no improvement in the physical properties of the rubber mixes are obtained.

Zinic oxide The rubber industry zinic oxide is second in important only to sulphur without Zinic oxide most organic accelerators will be not function property. Zinic oxide was be found in almost every compounding for activation of accelerators a small amounts 2 or 3 part of zinic oxide per 100 part of rubber.

Paraffin wax Acts as a softener, and helps processing by reducing adhesion to mill and rolling, blooming to the surface, protect the surface against ozone, and to reduce attack by chemicals such as oxidizing agents Stern, in 1972 [50]

4.3 Materials Specimens Preparation The steps of materials specimen preparation are explained below: 1- Prepare the materials which must be dough in the mixer according to standard measured quantities ,these dough was taken from standard of tires public company which called "Tread Dough" known as specifications, as follow:37

Table 4-1 Contents of Dough Material name

Quantity (gm)

Natural rubber

178.65

Carbon black

90.75

Dutrex oil

12.2

Zinic oxide

7.15

Stearic acid

3.57

OBTS

2.719

Sulphur

3.007

NOX

1.776

IPPV

2.98

Paraffin wax

3.5783

Sum

306.3803

2- The resin and the hardener were mixed at room temperature (25°C) at a ratio 2:1 according to weight, the mixing process was continued for (15minutes) until the mixture becomes homogenous and its temperature was raised. 3- Natural rubber which is prepared previously by special mixer was mixed with carbon black and epoxy resin for each percentage (0%, 20%, 40%, 60%, 80%, and 100%) from the filler (carbon black) and put in mixer; the mixing process was continued for 5 minutes until the mixture becomes homogenous and mix all the other components of dough with each others to become ready. 4- The dough was passing across in rolling process by two different speed rollers to produce a sheet with thickness about 2 mm as shown in the Fig.4-2

38

5- This sheet was left for about (24 hours) at room temperature (25°C) to obtain the optimum state for the dough. 6- The sheet then divided in to three equal parts. 7- A special mould was coated with silicon solution to prevent adhesion between sample and the moulds, mould dimensions are (14x14x2) cm. 8- The first part of the sheet will be vulcanize in the optimum condition of vulcanize (150 bar, 140ºC, 40 minutes) by a special mould prepares previously in the heated press as shown in the Fig.4-7. 9- The second part of the sheet will be left without vulcanize to test in this state. 10- The third part of the sheet will be reinforced by flax threads which are used in the tires industry 11- This procedure will be repeated for each percentage of epoxy resin.

4.4 Moulds Preparation To produce samples for the tests (Tensile, Compression and Hardness), one mould for each test is prepared with standard dimensions and then these moulds are used to make samples.

4.4.1 Tensile Test Specimens The tensile test specimens have been produced according to (ASTM D412-37) as shown with the standard dimensions in Fig.4-4a for: 1. Rubber vulcanize for each percentage. 2. Rubber without vulcanize for each percentages. 3. Rubber reinforcement by flax threads for each percentages. The tensile test specimens were produced using the mould shown in Fig.4-4b.

39

115 33 (mm) 6 (mm)

2 (mm)

a- Standard tensile test specimen

Figure 4 -3 Tensile Test Specimens

b- Device to cut tensile test specimen

Figure 4-4 tensile test specimen

40

4.4.2 Compression Test Specimens The compression test specimens have been produced according to (ASTM-D395-78) as shown with the standard dimensions in Fig.4-5 where the length to diameter ratio is approximately 1:2.

Spacers

Spacers test

13.2 mm

6.6 mm

Specimen

Washers

Figure 4- 5 Components of Compression Device

The compression test specimens were produced using the mould shown in Fig.4-5 and after solidification; the grinding processes were applied to the ends of each specimen to reduce friction between specimen ends and deforming tools.

41

4.4.3 Hardness Test Hardness is one of the properties which may be measured with out destruction or damage to the sample and is a most important characteristic of rubber and flexible plastics. The hardness of the latter is much more susceptible to temperature change than the former, the normal specified test temperature for measuring the hardness of rubber being 20+2ºC. An instrument used to measuring the hardness is called "Shore Durometer" as shown in the Fig.4-6, it is like other portable or pocket instrument and it is simply pressed on to sample and read the scale noted. This reading depends on the degree of penetration in to the sample of a spring loaded metal pointer; a very hard rubber a reading is about 90 to 95 and the soft rubbers reading down to about 30.

Figure 4-6 Shore Durometer

42

Figure 4-7 Heated Press Machine

43

Chapter Five Results and Discussion 5.1 Introduction This chapter displays the results of each test by curves and tables which are discussed to show the differences resulting from adding epoxy resin to the natural rubber with different percentages on

the mechanical properties;

tensile, compression, and others. The data is obtained from the mean results of three standard specimens for all tests.

5.2 Tensile Test Tensile test is one of the most used methods for determining the modulus of elasticity; yield tensile stress, yield strain, ultimate tensile strength and ductility of materials. The test involves an axial tensile load being applied to a standard specimen of rectangular cross section Fig.5-1 with a constant strain rate at about (100mm/min) by hydraulic tensile device shown in Fig.5-2 and this causes the specimen to elongate and finally fractured Fig.5-3.

0%

20%

40%

60%

80%

Figure 5-1 Tensile Specimens

44

100%

Figure 5.2 Computerized Test Meter

Fracture region

0%

20%

40%

60%

Figure 5-3 Tested Specimens

45

80%

100%

5.2.1 Tensile Test for standard vulcanized specimen The behavior of rubber when stretched constitutes one of the most important methods to investigate its physical properties. The common procedure is to stretch the rubber at a fixed and uniform rate, when expressed graphically the load which is applied and the elongation in the x-y axis. The load is often referred to as "stress" and the elongation as "strain ", the resultant graph begin known as a stress- strain curve. Figs.5-4 and 5-5 are typical of the graphs obtained with a vulcanized rubber. The curve may be divided in to three parts. First section is concave toward the elongation axis showing that the elongation here increases more rapidly than does load or stress. The second section of the curve is substantially straight whilst the third section is concave in the opposite direction to the first section. At the second section the load is increasing more rapidly than the elongation because of changes brought about in the rubber through stretching in this case the crystallization in the natural rubber occurs. Finally the rubber breaks. Figures 5-6 and 5-7 show a comparison between the standard curve of (0% epoxy) and the curve which (20% epoxy) added, this comparison shows the difference in the values of (stress – strain) and (load – elongation) curves ,which explain as ,the strain and elongation is increased against decreased in stress and load after add 20% epoxy to the standard specimen in the end of the first part of curve stress will be concentrated on area of cross section of specimen and its length increased rapidly ,then nicking accurse and continue until fracture in specimen, also show that the reduction in the area under the curve (by using Simpson’s rules and MathCAD program to determine) which mean toughness in Fig.5-6 and the work done by tensile in Fig.5-7 was decreased by 6.5% upon the standard that lead to conclusion that the material begin to change from ductile to brittle material . 46

Figures 5-8 and 5-9 show a change between the standard curve of (0% epoxy) and the curve which (40% epoxy) added which show that the load and stress values are decreasing and, also decreasing in the strain and elongation when increasing the percentage of epoxy resin because effect of amount of epoxy resin which made the material more brittle and also, there was high reduction in the percentage of toughness and work done by tensile test, these reduction reach to 33.7%. Figures 5-10 and 5-11 refer to the difference between the standard curve of (0% epoxy) and the curve which (60% epoxy) added, which show that rapidly decreasing in the values of stress and load and decreasing in the strain and elongation, increasing the percentage of epoxy resin to 60% due to rapidly reduction in the value of toughness and the work done was accrues arrive to 48.5% from the standard. Figures 5-12 and 5-13 illustrate the change between the standard curve of (0% epoxy) and the curve which percentage of (80% epoxy) added, which also show that the load and stress values are decreasing and the value of reduction in the toughness and the work done reach to 49.1% from the standard . Figures 5-14 and 5-15 refer to the difference between the standard curve of (0% epoxy) and the curve which percentage of (100% epoxy) added, which also show that the load and stress values are decreasing and the value of percentage reduction in the toughness and work done by tensile test equal to 56.7% . After all these comparisons, Figs.5-16 and 5-17 make a comparison among all the percentages with the standard curve to show the differences among them. These explained that the stress and load are decreasing; also strain and elongation are decreasing as well as increasing the percentages of epoxy resin against increasing percentage of reduction of toughness and work

47

done from 0% in the standard curve until it reach to 56.7% in 100% epoxy resin. Table 5-1 shows the values of the young modulus decreased from 4.8769 N/mm² in 0% epoxy resin to 1.2405 N/mm² in 100% epoxy resin, yield tensile stress decreased from 5.1333 N/mm² in 0% epoxy resin to 4.0111N/mm² in 100% epoxy resin, yield strain decreased from 204.6 to 13.653, yield load decreased 61.6N to 26N, yield elongations decreased, resilience increased, toughness decreased, work done decreased and percentage of reduction increased from 6.5% in 20% epoxy resin to 56.7% in 100% epoxy comparison with standard .

5.2.2 Tensile Test for unvulcanized specimen For unvulcanized rubber the general shape of the curve is approximately similar but the behavior is much more susceptible to changes in the test conditions than with vulcanized rubber. At increased temperatures the elongation at break of unvulcanized rubber is greatly increased and the tensile strength is slightly reduced. Figures 5-18 and 5-19 curves are divided in to three parts approximately similar to the vulcanized curves. First part is concave toward the elongation and strain axis showing that the elongation here increasing more rapidly than does load or stress, second part of the curve is substantially straight and third part is concave in the opposite direction to the first part of curve. In the second part strain and elongation is increased more rapidly than the stress and load, also find increased in resilience of material, increased toughness and increased in the percentage of increment in work done. Figures 5-20 and 5-21 show the difference between the standard unvulcanized curve and the curve for the material which added (20% of epoxy), then notice increasing in load and stress with decreasing in extension, 48

strain and rapidly increased in the percentage of increment in the toughness and work done which reach to 68% this show that the influence of adding epoxy resin change material to brittle which be tough. Figures 5-22 to 5-29 represent comparisons the curves of load– extension and curve of stress- strain for the percentages of epoxy (40%, 60%, 80% and 100%) added to unvulcanized rubber with the standard curve 0% epoxy and notice that load and stress increased when increased percentage of epoxy resin against extension and strain which decreased because material be brittle and tough ,then percentage of increment between standard and percentage of epoxy increased from 68.6 % in 40% epoxy to 89.4 % in 100% epoxy resin . Figures 5-30 and 5-31 show the difference among variables percentages of epoxy (20%, 40%, 60%, 80% and 100%) added to unvulcanized rubber and these refer to increasing in the stress and load against decreasing in strain and elongation, also increased in percentage of increment in the toughness and work done from 68 % in 20% epoxy to 89.4 % in 100% epoxy resin. Table 5-2 shows the values of the young modulus increased from 0.8382 N/mm² in 0% epoxy resin to 3.9444 N/mm² in 100% epoxy resin, yield tensile stress increased from 0.654 N/mm² in 0% epoxy resin to 1.282N/mm² in 100% epoxy resin, yield strain decreased from 16.372 to 5.635, yield load decreased 10.3N to 4.1N, yield elongations decreased , resilience increased, toughness increased, work done increased and percentage of increment increased from 68% in 20% epoxy resin to 89.4% in 100% epoxy comparison with standard .

49

5.2.3 Tensile Test for Reinforcement specimen The Reinforcement rubber was tested in this part of work. The specimen is reinforced by flax threads (the tensile strength for the flax threads alone was measured of 20.5 N/mm²) the curve behavior is much more susceptible to flax threads. Figures 5-32 and 5-33 these curves are divided in to two parts. First section is obey to Hooks law and approximately straight line, second section is concave toward of elongation and strain ,then load and stress increased on the cross section of specimen until the nicking accurse ,then fracture accurse and failed the specimen. Figures 5-34 and 5-35 show the difference between the standard reinforced curve and the curve for the material which added (20% of epoxy), then show an increase in the load applied and stress with decreasing in strain and extension because material take a brittle phase, also note that increased in the percentage of increment in toughness and work done by tensile to reach to 62.8% upon standard curve. Figures 5-36 to 5-43 represent comparisons of the curves of load – extension and curve of stress- strain for the percentages of epoxy (40%, 60%, 80% and 100%) added to reinforced rubber with the standard curve of 0% epoxy resin ,these curves show that the load and stress were increased as increased percentages of epoxy resin from (0% to 100%), also resilience and toughness increased and the percentages of increment in toughness and work done by tensile test increased from 62.8% in the 20% epoxy resin until reach to 137.4% in the 100% epoxy resin.

Figures 5-44 and 5-45 show the difference among variables percentages of epoxy (20%, 40%, 60%, 80% and 100%) added to reinforced rubber with standard curve 0% epoxy resin these refer to increasing in the stress and load 50

against decreasing in strain and elongation also toughness increased and the percentages of increment in toughness and work done by tensile test increased from 62.8% in the 20% epoxy resin until reach to 137.4% in the 100% epoxy resin.

Table 5-3 shows the values of the young modulus increased from 36.49 N/mm² in 0% epoxy resin to 45.12 N/mm² in 100% epoxy resin, yield tensile stress increased from 17.156 N/mm² in 0% epoxy resin to 27.472N/mm² in 100% epoxy resin, yield strain increased from 25.793 to 59.443, yield load increased from 128.8N to 466.5N, yield elongations increased from 10.317 to 31.777, resilience increased, toughness increased, work done increased and percentage of increment increased from 62.8% in 20% epoxy resin to 137.4% in 100% epoxy comparison with standard .

51

Table 5-1 Determination of tensile values for vulcanized rubber

Percentage of epoxy

young modulus N/mm²

yield tensile stress N/mm²

yield strain

yield load N

Standard (0%)

4.8769

5.1333

204.6

61.6

89.389

0.235

4.891

Work done by tensile N.mm 48.91

20% epoxy

3.495

4.9415

170.8

56.3

88.522

0.361

4.570

45.7

6.5%

40% epoxy

2.0229

4.6458

100.14

31.75

40.056

0.433

3.238

32.38

33.7%

60% epoxy

1.4712

4.5250

11.816

30.3

18.7265

0.523

2.517

25.17

48.5%

80% epoxy

1.2610

4.3167

15.206

31.8

16.0825

0.585

2.491

24.91

49.1%

100% epoxy

1.2405

4.0111

13.653

26.133

13.461

0.687

2.117

21.17

56.7%

yield Resilience Toughness elongation N/mm² N/mm² mm

52

Percentages of reduction

Table 5-2 Determination of tensile values for unvulcanized rubber yield strain

yield load N

yield elongation mm

0.8382

yield tensile stress N/mm² 0.654

16.372

10.30

5.490

0.13

0.379


20% epoxy

1.8083

1.153

10.343

9.70

4.137

0.133

0.638

6.38

68%

40% epoxy

2.2029

1.178

10.510

8.50

4.2040

0.146

0.639

6.39

68.6%

60% epoxy

2.9986

1.188

9.077

6.10

3.2310

0.207

0.657

6.57

73.3%

80% epoxy

3.1883

1.254

8.783

5.10

3.9130

0.219

0.687

6.87

81.2%

100% epoxy

3.9444

1.282

5.635

4.10

2.2540

0.228

0.718

7.18

89.4%

Percentage of epoxy


Standard (0%)

53

Resilience Toughness N/mm² N/mm²

Percentages of increment

Table 5-3 Determination of tensile values for Reinforced rubber yield strain

yield load N

yield elongation mm

Resilience N/mm²

Toughness N/mm²

36.49

yield tensile stress N/mm² 17.156

25.793

128.80

10.317

0.07

2.42


20% epoxy

37.96

18.789

51.982

338.2

20.793

0.122

3.94

39.4

62.8%

40% epoxy

38.88

19.194

52.067

345.5

20.827

0.135

4.549

45.49

87.9%

60% epoxy

39.26

20.544

53.773

343.80

25.510

0.192

4.634

46.34

91.4%

80% epoxy

43.17

24.522

58.345

461.80

27.338

0.197

5.56

55.6

129.7%

100% epoxy

45.12

27.472

59.443

466..5

31.777

0.203

5.745

57.45

137.4%

Percentage of epoxy


Standard (0%)

54

Percentages of increment

40.00 Standard Vulcanize [50, 51]

2

Stress(N/mm )

30.00

20.00

b

10.00

0.00 0.00

200.00

400.00

600.00

Strain

a Figure 5-4 a- Stress – Strain Curve for Standard 0% Epoxy Vulcanize Rubber b-Stress – Strain Curve for Standard Vulcanize Rubber [50, 51]

400.00 Standard [50, 51]

Load (N)

300.00

200.00

100.00

0.00 0.00

100.00

200.00

300.00

Extension (mm)

Figure 5-5 Load – Extension Curve for Standard 0% Epoxy Vulcanize Rubber

55

40.00 Standard Vulcanize [50, 51] 20% Epoxy

2

Stress(N/mm )

30.00

20.00

10.00

0.00 0.00

200.00

400.00

600.00

800.00

Strain

Figure 5-6 Comparison Stress – Strain Curve for Standard Vulcanize Rubber with 20% Epoxy 400.00 Standard [50, 51] 20% Epoxy

Load (N)

300.00

200.00

100.00

0.00 0.00

100.00

200.00

300.00

400.00

Extension (mm)

Figure 5-7 Comparison Load – Extension Curve for Standard Vulcanize Rubber with 20% Epoxy

56


2

Stress(N/mm )

30.00

20.00

10.00

0.00 0.00

200.00

400.00

600.00

Strain

Figure 5-8 Comparison Stress – Strain Curve for Standard Vulcanize Rubber with 40% Epoxy

400.00 Standard [50, 51] 40% Epoxy

Load (N)

300.00

200.00

100.00

0.00 0.00

100.00

200.00

300.00

Extension (mm)


57


2

Stress(N/mm )

30.00

20.00

10.00

0.00 0.00

200.00

400.00

600.00

Strain


400.00 Standard [50, 51] 60% Epoxy

Load (N)

300.00

200.00

100.00

0.00 0.00

100.00

200.00

300.00

Extension (mm)


58


2

Stress(N/mm )

30.00

20.00

10.00

0.00 0.00

200.00

400.00

600.00

Strain


400.00 Standard [50, 51] 80% Epoxy

Load (N)

300.00

200.00

100.00

0.00 0.00

100.00

200.00

300.00

Extension (mm)


59


2

Stress(N/mm )

30.00

20.00

10.00

0.00 0.00

200.00

400.00

600.00

Strain


400.00 Standard [50, 51] 100% Epoxy

Load (N)

300.00

200.00

100.00

0.00 0.00

100.00

200.00

300.00

Extension (mm)


60

40.00 Standard Vulcanize [50, 51] 20% Epoxy 40% Epoxy 60% Epoxy

30.00

80% Epoxy

2

Stress(N/mm )

100% Epoxy

20.00

10.00

0.00 0.00

200.00

400.00

600.00

800.00

Strain

Figure 5-16 Comparison Stress – Strain Curve for Standard Vulcanize Rubber with all Percentage of Epoxy

400.00 Standard [50, 51] 20% Epoxy 40% Epoxy 60% Epoxy

300.00

80% Epoxy

Load (N)

100% Epoxy

200.00

100.00

0.00 0.00

100.00

200.00

300.00

400.00

Extension (mm)

Figure 5-17 Comparison Load – Extension Curve for Standard Vulcanize Rubber with all Percentage of Epoxy

61

1.00 Standard unvulcanize [50,51]

2

Stress (N/mm )

0.80

0.60

0.40

0.20

0.00 0.00

100.00

200.00

300.00

400.00

500.00

Strain

Figure 5-18 Stress-Strain Curve for Standard 0% Epoxy Unvulcanize Rubber

16.00 Standard unvulcanize [50, 51]

Load (N)

12.00

8.00

4.00

0.00 0.00

50.00

100.00

150.00

200.00

250.00

Extension (mm)

Figure 5-19 Load – Extension Curve for Standard 0% Epoxy Unvulcanized Rubber

62

2.00 Standard unvulcanize [50,51] 20 % Epoxy

2

Stress (N/mm )

1.60

1.20

0.80

0.40

0.00 0.00

100.00

200.00

300.00

400.00

500.00

Strain

Figure 5-20 Comparison Stress – Strain Curve for Standard Unvulcanize Rubber with 20% Epoxy

16.00 Standard unvulcanize [50,51] 20% Epoxy

Load (N)

12.00

8.00

4.00

0.00 0.00

50.00

100.00

150.00

200.00

250.00

Extension (mm)

Figure 5-21 Comparison Load – Extension Curve for Standard Unvulcanize Rubber with 20% Epoxy

63

1.60 standard unvulcanize [50, 51] 40% Epoxy

2

Stress (N/mm )

1.20

0.80

0.40

0.00 0.00

100.00

200.00

300.00

400.00

500.00

Strain


20.00 Standard unvulcanize [50, 51] 40 % Epoxy

Load (N)

16.00

12.00

8.00

4.00

0.00 0.00

50.00

100.00

150.00

200.00

250.00

Extension (mm)


64


2

Stress (N/mm )

1.60

1.20

0.80

0.40

0.00 0.00

100.00

200.00

300.00

400.00

500.00

Strain



Load (N)

20.00

15.00

10.00

5.00

0.00 0.00

50.00

100.00

150.00

200.00

250.00

Extension (mm)


65


2

Stress (N/mm )

1.60

1.20

0.80

0.40

0.00 0.00

100.00

200.00

300.00

400.00

500.00

Strain



Load (N)

20.00

15.00

10.00

5.00

0.00 0.00

50.00

100.00

150.00

200.00

250.00

Extension (mm)


66


2

Stress (N/mm )

1.60

1.20

0.80

0.40

0.00 0.00

100.00

200.00

300.00

400.00

500.00

Strain

Figure 5-28 Comparison Stress – Strain Curve for Standard Unvulcanize Rubber with 100% Epoxy 25.00 Standard unvulcanize [50, 51] 100 % Epoxy

Load (N)

20.00

15.00

10.00

5.00

0.00 0.00

50.00

100.00

150.00

200.00

250.00

Extension (mm)


67

standard unvulcanize [50, 51]

2.00

20% Epoxy 40% Epoxy 60% Epoxy 80% Epoxy 100% Epoxy

2

Stress (N/mm )

1.50

1.00

0.50

0.00 0.00

100.00

200.00

300.00

400.00

500.00

Strain

Figure 5-30 Comparison Stress – Strain Curve for Standard Unvulcanize Rubber with all Percentage of Epoxy

Standard unvulcanize [50, 51] 20 % Epoxy 40 % Epoxy 60 % Epoxy 80 % Epoxy 100 % Epoxy

Load (N)

20.00

10.00

0.00 0.00

50.00

100.00

150.00

200.00

250.00

Extension (mm)

Figure 5-31 Comparison Load – Extension Curve for Standard Unvulcanize Rubber with all Percentage of Epoxy

68

12.00 Standard

2

Stress (N/mm )

8.00

4.00

0.00 0.00

40.00

80.00

120.00

Strain (%)

Figure 5-32 Stress – Strain Curve for Standard 0% Epoxy Reinforced Rubber

200.00 Standard

Load (N)

160.00

120.00

80.00

40.00

0.00 0.00

10.00

20.00

30.00

40.00

Extension (mm)

Figure 5-33 Load – Extension Carve for Standard 0% Epoxy Reinforced Rubber

69

25.00 Standard 20% Epoxy

2

Stress (N/mm )

20.00

15.00

10.00

5.00

0.00 0.00

40.00

80.00

120.00

Strain (%)

Figure 5-34 Comparison Stress – Strain Curve for Standard Reinforced Rubber with 20% Epoxy


Load (N)

300.00

200.00

100.00

0.00 0.00

10.00

20.00

30.00

40.00

Extension (mm)

Figure 5-35 Comparison Load – Extension Curve for Standard Reinforced Rubber with 20% Epoxy

70


2

Stress (N/mm )

20.00

15.00

10.00

5.00

0.00 0.00

40.00

80.00

120.00

Strain (%)



Load (N)

300.00

200.00

100.00

0.00 0.00

10.00

20.00

30.00

40.00

50.00

Extension (mm)


71


2

Stress (N/mm )

20.00

15.00

10.00

5.00

0.00 0.00

40.00

80.00

120.00

Strain (%)



Load (N)

300.00

200.00

100.00

0.00 0.00

10.00

20.00

30.00

40.00

Extension (mm)


72


2

Stress (N/mm )

20.00

15.00

10.00

5.00

0.00 0.00

40.00

80.00

120.00

Strain (%)



Load (N)

300.00

200.00

100.00

0.00 0.00

10.00

20.00

30.00

40.00

Extension (mm)


73


2

Stress (N/mm )

20.00

15.00

10.00

5.00

0.00 0.00

40.00

80.00

120.00

Strain (%)



Load (N)

200.00

100.00

0.00 0.00

10.00

20.00

30.00

40.00

Extension (mm)


74

2

Figure 5-44 Comparison Stress – Strain Curve for Standard Reinforced Rubber with all Percentage of Epoxy

Figure 5-45 Comparison Load – Extension Curve for Standard Reinforced Rubber with all Percentage of Epoxy

75

5-3 Hardness Test Hardness test is one of the important tests in the rubber industry for determining stiffness of the rubber. Also in this part Hardness was measured for all the percentages of epoxy added to the vulcanized, unvulcanized and reinforced rubber. Table 5-4 shows the values of the Hardness test to the vulcanized rubber and refers to the increased the Hardness towards when the percentages of the epoxy resin are increasing. This means that a hardness property was improved when added the epoxy.

Table 5-4 Values of the Hardness Test to the Vulcanized Rubber percentage of epoxy

Hardness value

Standard (0%)

62

20% epoxy

70

40% epoxy

81

60% epoxy

87

80% epoxy

92

100% epoxy

95

Table 5-5 represents the values of the Hardness test to the unvulcanized rubber and shows to the increased in the Hardness toward when the epoxy resin is added, this means that a hardness property was improved when the epoxy is added.

76

Table 5-5 Values of the Hardness Test to the Unvulcanized Rubber percentage of epoxy

Hardness value

Standard (0%)

25

20% epoxy

32

40% epoxy

52

60% epoxy

55

80% epoxy

72

100% epoxy

74

Table 5-6 show the values of the Hardness test to the reinforced rubber and also refer to the increased the Hardness when the epoxy resin is added, which means that a hardness property was improved when added the epoxy.

Table 5-6 Values of the Hardness Test to the Reinforced Rubber percentage of epoxy

Hardness value

Standard (0%)

37

20% epoxy

44

40% epoxy

60

60% epoxy

63

80% epoxy

72

100% epoxy

82

77

5.4 Compression Test Compression testing is one of the most used methods for testing the rubber intended for use in applications in which the rubber will be subjected to compressive stress in the air. When determining the compression set by the constant load method, the specimen in the form of a flat disc according to (ASTM-D395-78) is compressed by calibrated spring washers. In constant deflection methods a specimen of the same type is compressed to affix percentage of its original thickness by clamping it between rigid parallel plates fitted with distance pieces, the diminution in thickness is measured after a fixed period of compression and recovery. Table 5-7 represents the results of compression set by the constant deflection for the standard vulcanize rubber and five other percentages of epoxy resins which added to the natural rubber (20%, 40%, 60%, 80% and 100% ), then this table shows that the compression set is increasing proportionally with increasing the percentages of epoxy resin .

Table 5-7 Compression Set of Vulcanize Rubber Specimens Percentage of epoxy

Compression set (C) %

Standard (0%)

45

20% epoxy

75

40% epoxy

140

60% epoxy

165

80% epoxy

175

100% epoxy

180

78

Table 5-8 shows that the results of compression set by the constant deflection for the standard unvulcanize rubber and five other percentages of epoxy resin which added to the natural rubber (20%, 40%, 60%, 80% and 100%). This table shows that the compression set is decreasing with increasing the percentages of epoxy resin.

Table 5-7 Compression Set of unvulcanize Rubber Specimens Percentage of epoxy

Compression set (C) %

Standard (0%)

200

20% epoxy

190

40% epoxy

170

60% epoxy

150

80% epoxy

120

100% epoxy

110

79

Chapter Six Conclusions and Recommendations 6.1 Conclusions The main important conclusions that can be drawn from this work are as follows: 1- Particulate composite of natural rubber with epoxy resin is a new material, which can be used for different fields. 2- Increasing percentages of epoxy resin in the vulcanize rubber leads to a decrease in Young’s modulus for tensile test. 3- Increasing percentages of epoxy resin in unvulcanized and reinforced rubber leads to an increase in Young’s modulus for tensile test. 4- Yield stress for natural rubber with epoxy resin is decreased as increasing of percentages epoxy resin in vulcanize rubber for tensile. 5- Yield stress for natural rubber with epoxy resin is increased as increasing of percentages epoxy resin in unvulcanized and reinforced rubber for tensile. 6- Compression set for natural rubber with epoxy resin is increased as increasing of percentages epoxy resin in vulcanize rubber. 7- Compression set for natural rubber with epoxy resin is decreased as increasing of percentages epoxy resin in unvulcanized rubber. 8- Hardness values to vulcanized, unvulcanized and reinforced rubber were increased towards when the percentages of the epoxy resin increasing. 9- Resilience values to vulcanized, unvulcanized and reinforced rubber were increased towards when the percentages of the epoxy resin increasing.

80

10- Toughness for natural rubber with epoxy resin is decreased as increasing of percentages epoxy resin in vulcanize rubber and increased as increasing of percentages epoxy resin in unvulcanized and reinforced rubber. 11- Work done by tensile test for natural rubber with epoxy resin is decreased as increasing of percentages epoxy resin in vulcanize rubber and increased as increasing of percentages epoxy resin in unvulcanized and reinforced rubber. 12- Percentage of reduction in toughness to vulcanized rubber was increased towards when the percentages of the epoxy resin increasing. 13- Percentage of increment in toughness to unvulcanized and reinforced rubber was increased towards when the percentages of the epoxy resin increasing.

6.2 Recommendations 1. Study thermal conductivity for natural rubber with epoxy resin. 2. Investigate the wear and friction properties for natural rubber with epoxy resin. 3. Study the aging properties for natural rubber with epoxy resin. 4. Investigate the effect of temperature to the mechanical properties for standard and reinforced rubber. 5. Study the effect of particle size to the mechanical properties for standard and reinforced rubber.

81

References 1. William D.Callister, JR. "Material Science and Engineering An Introduction", Fifth Edition, 2000. 2. Ali H. Al-Hilli "Analysis and Experimental Study of High Velocity

Impact on Composite Plates", PhD, College of Engineering, Nahrain University, 2006. 3. Fred W.Billmeyer, JR; "Textbook of Polymer Science"; Professor of Analytical Chemistry, New York, Second Edition, (1971). 4. Marc Ander Meyers and Krishan Kumar Chawla,” Mechanical Behavior of Materials” (2000). 5. S.C. Sharma,”Composite Materials”,Narosa Publishing House, (2000). 6. Peter A. Thornton and Vito J. Colangelo, “Fundamentals of Engineering Materials”, (1986). 7. W. Bolten, “Engineering Materials Technology”, Third Edition, (1998). 8. Charles A. Harper "Handbook of Plastic and Elastomers", McGrawHill Book Company, Second Edition, 1975. 9. Dean M.Peters and Karyn L.Thomas, "Engineers Guide to Composite Materials", American society for metals, metals parck ; ohio 44073 ,1987. 10. Richard A. Flinn and Paul K. Trojan, “Engineering Materials and their Applications”, Third Edition, (1986). 11. G.S.Hollister and C.Thomas; "Fiber Reinforced Materials "; Elsevier, London (1966).

82

12. Sabodh K.Garg, vitas svalones Gerald A.Gurtman; "Analysis of Structural Composite Materials"; Marcel Decker, Inc. New York, (1973). 13. B.D.Agawal and J.N.Narang;" Strength and Failure Mechanism of Anisotropic Composite "; from J. "Fiber Science and Technology an International Journal", Vol.10, No.1 January (1977), p.37. 14. L.L.Clements and R.L.Moore;" Composite Properties for E-glass Fibers in a Room Temperature Epoxy Matrix ";Lawrence Livermore laboratory, university of California (94550), (1978). 15. Derek hill; "An Introduction to Composite Materials"; Professor of

Material Eng. University of Liverpool, Cambridge university press, England, (1981). 16. H.M.Lahiff; "Rubber–Toughened Epoxy Resins"; Department of Mechanical Engineering, University of Sydney, (1986). 17. F.J.Guild, P.J.Davy and P.J.Hogg;" Model for Unidirectional Composite in Longitudinal Tension and Compression "; Composite Science and Technology 36, (1988). 18. Peter C.Powell;" Engineering with Polymers"; Published by Chapman and Hill, (1992). 19. Pierre J. Minguet, Mark J.Fer and Christian K.Gunther;" Tests Methods for Textile Composites"; NASA Contractor Report 4609 July (1994). 20. S.D.Salman; " Tensile and Flexure Analysis of Multi-Layers Laminated Composite Materials"; M.Sc, College of Engineering, Al-Mustansiriyah University, (2002). 21. Abdul- Hakem Al-Zangna, “Study the Effect of Adding the Iraqi Ceramic Raw Material (Bauxite + Kaolin) to a Thermosetting Epoxy Resin on the Mechanical Properties”, M.Sc, Technology University, (2002).

83

22. Arkan Jawdat, “Study the Influence of Adding Copper Powder to a Thermosetting Epoxy Resin on the Mechanical Properties ", M.Sc, Nahrain University(2002),. 23. Husam A. Kereem,. “Study the Influence of Adding Nickel Powder to a Thermosetting Epoxy Resin on the Mechanical Properties”, M.Sc, Technology University, (2002). 24. Mawloud Hadi, "Mechanical Properties of Composites Using Aluminum Powder with Titanium Powder as a new Material for Mechanical Connections", M.Sc, Nahrain University, (2006). 25. Neogi C., Basu S.P., Bhowmick A.K. “Analysis of Rubber-Filler Interaction at High Temperature by Using Strain Amplification Factor,” Plastics and Rubber Processing and Applications, 12, 1989 pp. 147-151 26. Lake G.J., Lindley P.B., “Ozone Cracking, Flex Cracking and Fatigue of Rubber”, Rubber Journal, November, 1964 pp. 30-39. 27. Chung B., Funt J.M, Ouyang G.B. “Effects of Carbon Black on Elastomer Ultimate Properties – IR Compunds”, Rubber World, 204, 1991 pp. 46-51 28. Wang M.J. “Effect of Polymer-Filler and Filler-Filler Interactions on Dynamic Properties of Filled Vulcanizates” Rubber Chemistry and Technology, 71, 1998 pp. 520-589 29. Thomas A.G., Whittle J.M. “Tensile Rupture of Rubber” , Division of Rubber Chemistry, Rubber Chemistry and Technology, Buffalo, New York, October 14-17, 1969 pp.222-228 30. Goritz D., Kiss M.“On the Origin of Strain-Induced Crystallization,” Rubber Chemistry and Technology, 59, 1985, pp. 40-45 31. Allegra G.,“Strain-Induced Crystallization in Rubbers” , Polymer Preprints, 26, 2, 1985 pp. 42

84

32. Allegra G., “Strain-Induced Crystallization in Rubber” , Rubbercon, 1987 pp. 21A/1 – 21A/7 33. Flory P.J., Journal of Chemical Physics, 15, 1947 pp.397 34. Mitchell G.R. “A Wide-Angle X-Ray Study of the Development of Molecular Orientation in Crosslinked Natural Rubber” , Polymer, 25, 11, 1984 pp. 1562-1572 35. Dubault A., Delocke B., Herz J. “Effect of Crosslinking Density on the Orientational Order Generated in Strained Networks: A Deuterium Magnetic Resonance Study”, Polymer, 25, 10,1984 pp. 1405-1410 36. Mitchell G.R., Brown D.J., Windle A.H. “The Interpretation of Orientation-Strain Relationships in Rubbers and Thermoplastic” Polymer, 36,1985 pp1755-1762 37. Udagawa Y., Ito M. “Detection of the Molecular Orientation in Nonvulcanized and Vulcanized Natural Rubber Compounds by the Low-Temperature

X-Ray

Method”,Rubber

Chemistry

and

Technology, 62, 1989 pp. 179-195 38. Queslel J.P., Monnerie L., Erman B. “Characterization of Segmental Orientation in Stretched Rubbery Networks by the Stationary Fluorescence Polarization Technique”, Journal of Macromolecular Science and Chemistry A, 26, 1, 1989 pp 93-123 39. Xingfa M., Chongguang W. “Indirect Evidence on Molecular Orientation Behavior of Metal-to-Rubber Adhesive Bonding in Vulcanization”, PMSE: Polymeric Materials, Science & Engineering, 10, 5, 1994 pp. 132-135 40. Fleischman T., The Goodyear Tire and Rubber Company, personal communication, 2000

85

41. Breidenbach R.F., Lake G.J. “Mechanics of Fracture in Two-Ply Laminates,” Rubber Chemistry and Technology, 52, 1979, pp 96-109 42. Gent A.N., Fielding-Russell G.S., Livingston D.I., Nicholson D.W. “Failure of Cord-Rubber Composites by Pull-Out of Transverse Fracture,” Journal of Materials Science, 16, 1981 pp.949-956 43. Huang Y.S., Yeoh O.H. “Crack Initiation and Propagation in Model Cord-Rubber Composites”,Rubber Division, American Chemical Society, Cincinatti, Ohio, October 18-21, 1988 pp. 709-731 44. Lee B.L., Liu D.S. “Cumulative Damage of Fiber-Reinforced Elastomer Composites under Fatigue Loading”,Journal of Composite Materials, 28, 13, 1994 pp. 1261-1286 45. Martin R.H. “Incorporating Interlaminar Fracture Mechanics Into Design,” Proc. Instn. Mech Engrs., 214, L 2000 pp. 91-97 46. Reirhart T.J., Dostal C.A., Woods .M.S.,Frissell H.J.,Ronk A.W. , Jenkins D.M.,Okeete K.L.,Pilarezyk K.L.,Stedfeld R.L. and Mills K.M. " Engineered Material Handbook. Volume 1, Composite "ASTM International, (1987). 47. Harmar E. Davis, George Earl Troxell and George F. W. Hauck,” The Testing of Engineering Materials”, McGraw- Hill, Inc, (1982). 48. E. J. Hearn, “Mechanics of Materials”, volume 2, Second Edition, Pergamon press, (1985). 49. Annual Book of ASTM Standards,Part 37"Rubber Natural and Synthetic –General Test Methods; Carbon Black",, 1979 50. H. J. Stern "Natural Rubber and Synthetic" Second Edition, 1972 pp.467- 468. 51. Maurice Morton "Rubber Technology ", Second Edition, 1973, Litton Educational Publishing, Inc.

86

‫ﺷﻜﺮ و ﺗﻘﺪﻳﺮ‬ ‫اﻟﺤﻤﺪ ﷲ ﻋﻠﻰ ﻣﺎ أﻧﻌﻢ و ﻟﻪ اﻟﺸﻜﺮ ﻋﻠﻰ ﻣﺎ أﻟﻬﻢ و اﻟﺜﻨﺎء ﺑﻤﺎ ﻗﺪم‬ ‫ﻳ ﻮد اﻟﺒﺎﺣ ﺚ أن ﻳﻌﺒ ﺮ ﻋ ﻦ ﺧ ﺎﻟﺺ ﺷ ﻜﺮﻩ و إﻣﺘﻨﺎﻧ ﻪ اﻟ ﻰ اﻻﺳ ﺘﺎذ اﻟﻤ ﺸﺮف‬ ‫اﻟ ﺪآﺘﻮر ﻣﺤ ﺴﻦ ﺟﺒ ﺮ ﺟ ﻮﻳﺞ و اﻟ ﺪآﺘﻮر ه ﺎﻧﻲ ﻋﺰﻳ ﺰ اﻣ ﻴﻦ ﻟﻤ ﺎ أﺑ ﺪﻳﺎﻩ ﻣ ﻦ ﻧ ﺼﺢ ﺳ ﺪﻳﺪ‬ ‫و ﺗﻮﺻﻴﺎت ﺣﻜﻴﻤﺔ ﻷﺟﻞ إﻋﺪاد هﺬا أﻟﺒﺤ ﺚ‪ ،‬آﻤ ﺎ و ﻳﺘﻘ ﺪم ﺑﺎﻟ ﺸﻜﺮ اﻟ ﻰ اﻟﻜ ﺎدر اﻻداري ﻓ ﻲ‬ ‫ﻗﺴﻢ اﻟﻬﻨﺪﺳﺔ اﻟﻤﻴﻜﺎﻧﻴﻜﻴﺔ وﻋﻤﺎدة آﻠﻴﺔ اﻟﻬﻨﺪﺳﺔ ‪.‬‬ ‫و ﻳﻮد أﻳﻀﺎ ﺷﻜﺮ اﻟﻜﻮادر اﻻدارﻳ ﺔ و اﻟﻔﻨﻴ ﺔ ﻓ ﻲ اﻟ ﺸﺮآﺔ اﻟﻌﺎﻣ ﺔ ﻟﻠ ﺼﻨﺎﻋﺎت اﻟﻤﻄﺎﻃﻴ ﺔ‬ ‫ﻓﻲ اﻟﺪﻳﻮاﻧﻴﺔ وﺧﺎﺻﺔ ﻗﺴﻢ اﻟﻤﺨﺘﺒﺮات ﻟﻤﺎ ﻗﺪﻣﻮﻩ ﻣﻦ ﻣﺴﺎﻋﺪة ﻓﻲ اﻋﺪاد هﺬا اﻟﺒﺤﺚ ‪.‬‬ ‫آﻤ ﺎ ﻳ ﻮد ﺷ ﻜﺮ ﻋﺎﺋﻠﺘ ﻪ اﻟﻐﺎﻟﻴ ﺔ و أﺻ ﺪﻗﺎﺋﻪ اﻻﻋ ﺰاء ﻟﻤ ﺎ ﺗﺤﻤﻠ ﻮا واﻟ ﺬﻳﻦ ﻗ ﺪﻣﻮا ﻣ ﺎ‬ ‫ﺑﻮﺳﻌﻬﻢ ﻻﺗﻤﺎم هﺬا اﻟﻌﻤﻞ‪.‬‬

‫اﻟﺒﺎﺣﺚ‬ ‫ﻧﺒﻴﻞ ﺷﻼل ﺛﺎﻣﺮ اﻟﻤﺮﻣﻀﻲ‬ ‫‪2007‬‬

‫ﻣﻠﺨﺺ اﻟﺒﺤﺚ‬ ‫اﻟﺨﻮاص اﻟﻤﻴﻜﺎﻧﻴﻜﻴﺔ ﻟﺜﻼﺛﺔ اﻧﻮاع ﻣﻦ اﻟﻤﻄﺎط اﻟﻄﺒﻴﻌﻲ ) اﻟﻤﻔﻠﻜﻦ‪ ،‬اﻟﻐﻴﺮ اﻟﻤﻔﻠﻜﻦ واﻟﻤﻄﺎط‬ ‫اﻟﻤﻘﻮى( ﻗﺪ درﺳﺖ ﻓﻲ هﺬا اﻟﺒﺤﺚ ‪،‬وآﻞ ﻧﻮع ﻣﻦ اﻻﻧﻮاع اﻟﺜﻼﺛﺔ اﺧﺬ ﺑﺴﺖ ﻧﺴﺐ ﻣﻦ راﺗﻴﻨﺞ اﻻﻳﺒﻮآﺴﻲ‬ ‫)ﺻﻔﺮ‪ %80،%60،%40،%20،%‬و‪ (%100‬واﻟﻌﻴﻨﺎت ﺻﻨﻌﺖ ﻓﻲ اﻟﺸﺮآﺔ اﻟﻌﺎﻣﺔ ﻟﻼﻃﺎرات ﻓﻲ‬ ‫اﻟﺪﻳﻮاﻧﻴﺔ ﺑﺄﺳﺘﺨﺪام اﺣﺪى ﻋﺠﻨﺎت اﻻﻃﺎرات وﺗﺪﻋﻰ )‪.(Tread Dough‬‬ ‫ﻗﻴﻢ ﻣﻌﺎﻣﻞ اﻟﻤﺮوﻧﺔ آﺎن ﻟﻬﺎ اآﺒﺮ اﻧﺨﻔﺎض ﻓﻲ ﺣﺎﻟﺔ اﻟﻤﻄﺎط اﻟﻤﻔﻠﻜﻦ وﺻﻞ اﻟﻰ ‪، %74.5‬‬ ‫واﻋﻠﻰ ارﺗﻔﺎع آﺎن ﻟﻬﺎ ﻓﻲ ﺣﺎﻟﺔ اﻟﻤﻄﺎط اﻟﻐﻴﺮ اﻟﻤﻔﻠﻜﻦ واﻟﻤﻄﺎط اﻟﻤﻘﻮى وﺻﻞ اﻟﻰ ‪ %317.5‬و‬ ‫‪ %23.5‬ﻋﻠﻰ اﻟﺘﻮاﻟﻲ آﺬﻟﻚ ﻗﻴﻢ اﺟﻬﺎد اﻟﺨﻀﻮع واﻧﻔﻌﺎل اﻟﺨﻀﻮع وﻣﻘﺎوﻣﺔ اﻟﺸﺪ آﺬﻟﻚ ﺣﺴﺒﺖ ﻟﻜﻞ‬ ‫ﺣﺎﻟﺔ ﻣﻦ اﻟﺤﺎﻻت وﻟﺠﻤﻴﻊ ﻧﺴﺐ راﺗﻴﻨﺞ اﻻﻳﺒﻮآﺴﻲ‪.‬‬ ‫ﻗﻴﻢ اﻟﻤﺮوﻧﺔ او اﻻرﺗﺪادﻳﺔ‪ ،‬اﻟﺸﻐﻞ اﻟﻤﻨﺠﺰ ﻣﻦ ﻓﺤﺺ اﻟﺸﺪ و اﻟﺼﻼدة وﻣﻘﺪار اﻟﻨﺴﺒﺔ اﻟﻤﺌﻮﻳﺔ‬ ‫اﻟﺨﺴﺎرة واﻟﺮﺑﺢ ﻓﻲ اﻟﺼﻼدة اﻳﻀًﺎ ﺣﺴﺒﺖ وآﺎﻧﺖ اﻟﻨﺴﺐ ‪:‬ﻓﻲ ﺣﺎﻟﺔ اﻟﻤﻄﺎط اﻟﻤﻔﻠﻜﻦ ﻧﺴﺒﺔ اﻟﺨﺴﺎرة ﺑﻴﻦ‬ ‫)‪ %6.5‬اﻟﻰ ‪ (%56.7‬وﻓﻲ اﻟﻤﻄﺎط اﻟﻐﻴﺮ اﻟﻤﻔﻠﻜﻦ واﻟﻤﻄﺎط اﻟﻤﻘﻮى آﺎﻧﺖ ﻧﺴﺒﺔ اﻟﺮﺑﺢ ﺑﻴﻦ )‪%68‬‬ ‫اﻟﻰ ‪ (%89.4‬و)‪ %62.8‬اﻟﻰ ‪ (%137.4‬ﻋﻠﻰ اﻟﺘﻮاﻟﻲ ‪ ،‬هﺬﻩ اﻟﻘﻴﻢ ﺣﺴﺒﺖ ﺑﺄﺳﺘﺨﺪام‬ ‫) ‪ (Simpson’s rules‬وﺑﺮﻧﺎﻣﺞ )‪.( MathCAD‬‬ ‫اﻟﺼﻼﺑﺔ آﺬﻟﻚ درﺳﺖ ﻓﻲ اﻧﻮاع اﻟﻤﻄﺎط اﻟﺜﻼﺛﺔ اﻟﻤﻔﻠﻜﻦ واﻟﻐﻴﺮ اﻟﻤﻔﻠﻜﻦ واﻟﻤﻘﻮى وﻟﺠﻤﻴﻊ ﻧﺴﺐ‬ ‫راﺗﻴﻨﺞ اﻻﻳﺒﻮآﺴﻲ ‪ ،‬ووﺟﺪ ان اﻟﺼﻼﺑﺔ ﺗﺰداد ﻃﺮدﻳًﺎ ﻣﻊ زﻳﺎدة ﻧﺴﺒﺔ راﺗﻴﻨﺞ اﻻﻳﺒﻮآﺴﻲ وﺗﺘﺮاوح ﻓﻲ‬ ‫اﻟﻤﻄﺎط اﻟﻤﻔﻠﻜﻦ ﺑﻴﻦ )‪ %62‬اﻟﻰ ‪ (%95‬واﻟﻐﻴﺮ اﻟﻤﻔﻠﻜﻦ ﺑﻴﻦ )‪ %25‬اﻟﻰ ‪ (%74‬وﻓﻲ اﻟﻤﻘﻮى ﺑﻴﻦ‬ ‫)‪ %37‬اﻟﻰ ‪. (%82‬‬ ‫ﺟﻬﺎز اﻧﻀﻐﺎط ﺧﺎص ﺻﻨﻊ ﻃﺒﻘًﺎ اﻟﻰ ﻟﻠﻤﻮاﺻﻔﺎت اﻟﻘﻴﺎﺳﻴﺔ ﻓﻲ ‪ ASTM‬ﻟﻐﺮض ﻓﺤﺺ ﻋﻴﻨﺎت‬ ‫اﻻﻧﻀﻐﺎط ﺑﺄﺳﺘﺨﺪام ﻃﺮﻳﻘﺔ اﻻﻧﻀﻐﺎط اﻟﺴﺎآﻦ‪،‬اﻻﻧﻀﻐﺎﻃﻴﺔ ﺣﺴﺒﺖ ﻣﻦ اﻟﺘﺠﺎرب ووﺟﺪ ﺗﺎﺛﻴﺮ اﺿﺎﻓﺔ‬ ‫راﺗﻴﻨﺞ اﻻﻳﺒﻮآﺴﻲ اﻟﻰ اﻟﻤﻄﺎط اﻟﻄﺒﻴﻌﻲ‪ ،‬ذﻟﻚ وﺿﺢ ان ﻗﻴﻤﺔ اﻻﻧﻀﻐﺎﻃﻴﺔ ﺗﺰداد ﺑﺰﻳﺎدة ﻧﺴﺒﺔ راﺗﻴﻨﺞ‬ ‫اﻻﻳﺒﻮآﺴﻲ ﻓﻲ ﺣﺎﻟﺔ اﻟﻤﻄﺎط اﻟﻤﻔﻠﻜﻦ ﺑﻴﻦ )‪ %45‬اﻟﻰ ‪، (%180‬اﻣﺎ ﻓﻲ ﺣﺎﻟﺔ اﻟﻤﻄﺎط اﻟﻐﻴﺮ اﻟﻤﻔﻠﻜﻦ‬ ‫ﻓﺎﻧﻬﺎ ﺗﻨﺨﻔﺾ ﺑﺰﻳﺎدة ﻧﺴﺒﺔ اﻻﻳﺒﻮآﺴﻲ ﺑﻴﻦ )‪ %200‬اﻟﻰ ‪.(%110‬‬