characteriztion of arall comp

CHAPTER 1

INTRODUCTION TO THESIS

Al break at 10^6 and arall don’t at limit of 10^7

1.1 Introduction to thesis:This thesis consists of following basic chapter

1. Introduction to composites2. Literature review3. Introduction to ARALL4. Manufacturing off ARALL5. Introduction to testing of composites6. Mechanical testing of ARALL composite

Now starting with introduction to composite in this chapter we discussed following

1.2 Composites:

Composite materials are engineered materials made from two or more constituent materials that remain separate and distinct while forming a single component [1].

Classification of composites:

Composites have basically types according to their nature

1.2.1 by disperse phase

It has 3 types

1. Particle reinforced2. Structural 3. Fiber reinforced

1.2.2. by matrix composite

It has 3 types

1. Polymer matrix composite2. Metal matrix composite3. Ceramic matrix composite

Further we studied about the hybrid composite

1.3 Hybrid composite:

It is actually incorporation of two or more fibres within a single matrix the resulting material is a hybrid composite [2].Classification of hybrid composite:

1. Interply or tow-by-tow2. Sandwich hybrids, also known as core-shell3. Interply or laminated4. Intimately mixed hybrids

Our concerned type among hybrid composite is laminated one.

1.3.1 Interply laminated:

In which alternate layers of the two (or more) materials are stacked in a regular manner.

Now the basic type of laminated is FIBER METAL LAMINATES (FML’s)

1.3.2 Fiber Metal Laminate:

Fiber metal laminates (FMLs) are hybrid composite structures based on thin sheets of metal alloys and plies of fiber reinforced polymeric materials [3].

There are 3 basic types of FML’s

1. ARALL2. CARALL 3. GLARE

Now our area of concern is ARALL so we discuss the Arall .

1. What is Arall?2. How to manufacture?3. How to do test 4 point bending (monotonic and fatigue) and what are the results?

1.3.2.1 What is ARALL?

ARAMID FIBRE RIENFORCED ALUMINUM ALLOY LAMINATES(ARALL) are a new class of hybrid materials which consist of alternating layers of thin Isotropic high-strength aluminum alloy sheets bonded by a structural metal adhesive impregnated with high-strength aramid fibers [4].

Figure1: ARAMID reinforced aluminum laminate

1.3.2.2 How to manufacture?

To manufacture the Arall we did following steps as follows

1. Cutting2. Mechanical Degreasing3. Alkaline degreasing4. De-oxidation5. Electrochemical treatment6. Hand lay up7. Compression molding8. Post curing9. Cutting of sample

So by doing all these steps we got the specimens as shown in fig.

Figure 2: 5 specimens of ARALL composite

1.4 Testing:

We did 4 point bending test procedure

1. Monotonic loading2. Fatigue loading on 4000 cycles

By doing monotonic loading we got the maximum loading at which the delamination occurs then by applying the fatigue loading on the specimen limiting the load up to (20 to 60)% and (20 to 80)% range in compression-compression cycle. After that we get results by plotting graphs.

1. LOAD VS DISLPLACEMENT2. LOAD VS CYCLES

CHAPTER 2

INTRODUCTION TO COMPOSITES

2. Introduction

2.1 Overview of composites

Over the last thirty years composite materials plastics and ceramics have been the dominant

emerging materials. The volume and number of applications of composite materials have grown

steadily penetrating and conquering new markets relentlessly. Modern composite materials

constitute a significant proportion of the engineered materials market ranging from everyday

products to sophisticated applications. While composites have already proven their worth as

weight saving materials the current challenge is to make them cost effective [5]. The efforts to

produce economically attractive composite components have resulted in several innovative

manufacturing techniques currently being used in the composites industry. It is obvious

especially for composites that the improvement in manufacturing technology alone is not enough

to overcome the cost hurdle.

The composites industry has begun to recognize that the commercial applications of composites

promise to offer much larger business opportunities than the aerospace sector due to the sheer

size of transportation industry. Thus the shift of composite applications from aircraft to other

commercial uses has become prominent in recent years. Increasingly enabled by the introduction

of newer polymer resin matrix materials and high performance reinforcement fibers of glass

carbon and aramid the penetration of these advanced materials has witnessed a steady expansion

in uses and volume. The increased volume has resulted in an expected reduction in costs [6].

High performance FML can now be found in such diverse applications as composite armoring

designed to resist explosive impacts fuel cylinders for natural gas vehicles, windmill blades,

industrial drive shafts, support beams of highway bridges and even paper making rollers. For

certain applications the use of composites rather than metals has in fact resulted in savings of

both cost and weight.

2.1.1 Applications:

1. The aerospace industry (structural components as well as engines and motors)

2. Automotive parts (panels, frames, dashboards, body repairs)

3. Sinks, bathtubs, hot tubs, swimming pools

4. Cement buildings, bridges

5. Surfboards, snowboards

6. Golf clubs, fishing poles, hockey sticks

7. Cascades for engines

8. Curved fairing and fillets

9. Replacements for welded metallic parts

10. Cylinders

11. Tubes

12. Ducts

13. Blade containment bands

Figure 3: application of composite in Aircraft

Further the need of composite for lighter construction materials and more seismic resistant

structures has placed high emphasis on the use of new and advanced materials that not only

decreases dead weight but also absorbs the shock and vibration through tailored

microstructures [7].

Figure 4: composite in CNG cylinders

Unlike conventional materials (steel) the properties of the composite material can be designed

considering the structural aspects. The design of a structural component using composites

involves both material and structural design.

Figure 5: Relative importance of material development through history [8]

Composite properties (stiffness, thermal expansion etc.) can be varied continuously over a broad

range of values under the control of the designer. Careful selection of reinforcement type enables

finished product characteristics to be tailored to almost any specific engineering requirement .

2.2 Definition of composite:

The most widely used meaning is the following one which has been stated by

Jartiz “Composites are multifunctional material systems that provide characteristics not

obtainable from any discrete material. They are cohesive structures made by physically

combining two or more compatible materials different in composition and characteristics and

sometimes in form”.

The weakness of this definition resided in the fact that it allows one to classify among the

composites any mixture of materials without indicating either its specificity or the laws which

should give it which distinguishes it from other very banal meaningless mixtures.

Kelly very clearly stresses that the composites should not be regarded simple as a combination of

two materials. In terms of strength to resistance to heat or some other desirable quality it is better

than either of the components alone or radically different from either of them.

Figure 6: composite material

Beghezan defines as “The composites are compound materials which differ from alloys by the

fact that the individual components retain their characteristics but are so incorporated into the

composite as to take advantage only of their attributes and not of their short comings” in order to

obtain improved materials .

Van Suchetclan explains composite materials as heterogeneous materials consisting of two or

more solid phases which are in intimate contact with each other on a microscopic scale. They can

be also considered as homogeneous materials on a microscopic scale in the sense that any

portion of it will have the same physical property [9].

2.3 Merits of Composites:

Advantages of composites over their conventional counterparts are the ability to meet diverse

design requirements with significant weight savings as well as strength to weight ratio. Some

advantages of composite materials over conventional ones are as follows [10]:

1. Tensile strength of composites is four to six times greater than that of steel or aluminum.

2. Improved torsional stiffness and impact properties.

3. Higher fatigue endurance limit (up to 60% of ultimate tensile strength).

4. 30% - 40% lighter for example any particular aluminum structures designed to the same

functional requirements e.g Al=15gram, arall=6gram

5. Lower embedded energy (sum of energy consumption) compared to other structural

metallic materials like steel, aluminum etc.

6. Composites are less noisy while in operation and provide lower vibration transmission

than metals.

7. Composites are more versatile than metals and can be tailored to meet performance needs

and complex design requirements.

8. Long life offer excellent fatigue, impact, environmental resistance and reduce

maintenance.

9. Composites enjoy reduced life cycle cost compared to metals.

10. Composites exhibit excellent corrosion resistance.

11. Improved appearance with smooth surfaces and readily incorporable integral decorative

melamine are other characteristics of composites.

12. Composite parts can eliminate joints / fasteners providing part simplification and

integrated design compared to conventional metallic parts.

2.4 Characteristics of the Composites:

A composite material consists of two phases. It consists of one or more discontinuous phases

embedded in a continuous phase. The discontinuous phase is usually harder and stronger than the

continuous phase and is called the reinforcement whereas the continuous phase is termed as the

matrix [11].

2.4.1Terminology of composite material:

Many composite materials are composed of just two phases

1. Matrix

2. Dispersed phase

2.4.1.1 Matrix:

It is continuous and surrounds the dispersed phase.

2.4.1.2 Dispersed phase:

The phase which is surrounded by the matrix.

Figure 7: matrix and dispersed phase [12]

The matrix is usually more ductile and less hard. It holds the dispersed phase and shares a load

with it. Matrix is composed of any of the three basic material type i.e. polymers, metals or

ceramics. The matrix forms the bulk form or the part or product. The secondary phase embedded

in the matrix is a discontinuous phase. It is usually harder and stronger than the continuous

phase. It servers to strengthen the composites and improves the overall mechanical properties of

the matrix.

Properties of composites are strongly dependent on the properties of their constituent materials

their distribution and the interaction among them. The composite properties may be the volume

fraction sum of the properties of the constituents or the constituents may interact in a synergistic

way resulting in improved or better properties. Apart from the nature of the constituent materials

the geometry of the reinforcement influences the properties of the composite to a great extent.

The concentration distribution and orientation of the reinforcement also affect the properties. The

properties of composites are a function of the properties of the constituent phases their relative

amount and the geometry of the dispersed phase.

Figure 8: dispersed phase that may influence the properties of composite [13]

The shape of the discontinuous phase the size and size distribution and volume fraction

determine the interfacial area which plays an important role in determining the extent of the

interaction between the reinforcement and the matrix.

Concentration usually measured as volume or weight fraction determines the contribution of a

single constituent to the overall properties of the composites. It is not only the single most

important parameter influencing the properties of the composites but also an easily controllable

manufacturing variable used to alter its properties.

2.5. Classification of composite material:

2.5.1. By dispersed phase:

One simple scheme for the classification of composite materials with respect to dispersed phase

is shown in Figure which consists of three main divisions: particle-reinforced, fiber-reinforced

[14].

Figure 9: Classification of Composites

1. Particle reinforced composite:

In this type the dispersed phase for particle-reinforced composites is equiaxed.it means the

particle dimensions are approximately the same in all directions.

Figure 10: Particle reinforced composite

2. Fiber reinforced composite:

In this type the dispersed phase has the geometry of a fiber it means a large length-to-diameter

ratio.

Figure 11: fiber reinforced composite and types

3. Structural composites:

These are combinations of composites and homogeneous materials.

Figure 12: structural composite

2.5.2. By matrix:

The matrix phase of fibrous composites may be a metal, polymer, or ceramic. In general, metals

and polymers are used as matrix materials because some ductility is desirable; for ceramic matrix

composites the reinforcing component is added to improve fracture toughness [15].

Figure 13: classification with respect to matrix phase

1. Polymer Matrix Composites:

Most commonly used matrix materials are polymeric. In general the mechanical properties of

polymers are inadequate for many structural purposes. In particular their strength and stiffness

are low compared to metals and ceramics. These difficulties are overcome by reinforcing other

materials with polymers. Secondly the processing of polymer matrix composites need not

involve high pressure and doesn’t require high temperature. Also equipment’s required for

manufacturing polymer matrix composites are simpler. For this reason polymer matrix

composites developed rapidly and soon became popular for structural applications [16].

Figure 14: PMC

Composites are used because overall properties of the composites are superior to those of the

individual components for example polymer/ceramic. Composites have a greater modulus than

the polymer component but aren’t as brittle as ceramics.

a. Glass Fiber-Reinforced Polymer (GFRP) Composites:

Fiberglass is simply a composite consisting of glass fibers either continuous or discontinuous,

contained within a polymer matrix.

Figure 15: Glass fiber reinforced polymer [17]

b. Carbon Fiber-Reinforced Polymer (CFRP) Composites:

Carbon is a high-performance fiber material that is the most commonly used reinforcement in

advanced polymer-matrix composites.

Figure 16: Carbon reinforced polymer

c. Aramid Fiber-Reinforced Polymer Composites

Aramid fibers are high-strength, high-modulus materials. They are especially desirable for their

outstanding strength-to weight ratio which is superior to metals

Figure 17: Schematic representation of repeat unit and chain structures for aramid (Kevlar)

fibers.

2. Metal Matrix Composites

Metal Matrix Composites have many advantages over monolithic metals like higher specific

modulus, higher specific strength, better properties at elevated temperatures, and lower

coefficient of thermal expansion. Because of these attributes metal matrix composites are under

consideration for wide range of applications.

Figure 18: Metal matrix composite

3. Ceramic matrix Composites

One of the main objectives in producing ceramic matrix composites is to increase the toughness.

Naturally it is hoped and indeed often found that there is improvement in strength and stiffness

of ceramic matrix composites [18].

Figure 19: Ceramic matrix Composite

2.6. Hybrid Composites:

A relatively new fiber-reinforced composite is the hybrid which is obtained by using two or more

different kinds of fibers in a single matrix [19].

Hybrids have a better all-around combination of properties than composites containing only a

single fiber type. A variety of fiber combinations and matrix materials are used but in the most

common system both carbon and glass fibers are incorporated into a polymeric resin. The carbon

fibers are strong and relatively stiff and provide low density reinforcement however they are

expensive. Glass fibers are inexpensive and lack the stiffness of carbon. The glass carbon hybrid

is stronger and tougher has a higher impact resistance and may be produced at a lower cost than

either of the comparable all carbon or all-glass reinforced plastics.

There are a number of ways in which the two different fibers may be combined which will

ultimately affect the overall properties.

For example:

The fibers may all be aligned and intimately mixed with one another or laminations may be

constructed consisting of layers each of which consists of a single fiber type alternating one with

another. In virtually all hybrids the properties are anisotropic.

When hybrid composites are stressed in tension failure is usually no catastrophic. The carbon

fibers are the first to fail at which time the load is transferred to the glass fibers. Upon failure of

the glass fibers the matrix phase must sustain the applied load.

2.6.1 Principal applications:

Hybrid composites have following application [20].

1. Lightweight land, water and air transport structural components

2. Sporting goods, and lightweight orthopedic Components.

2.6.2 Classification of Hybrid Composite

1. Interply or tow-by-tow:

In which tows of the two or more constituent types of fiber are mixed in a regular or random

manner.

Figure 20: Interply or tow-by-tow hybrid composite [21]

2. Sandwich hybrids also known as core-shell:

In which one material is sandwiched between two layers of another.

Figure 21: Sandwich hybrids

3. Interply or laminated (layer by layer)

In which the alternate layers of the two (or more) materials are stacked in a regular manner.

Figure 22: Interply or laminated (layer by layer)

4. Intimately mixed hybrids:

In which the constituent fibers are made to mix as randomly as possible so that no over-

concentration of any one type is present in the material.

2.6.2.1 Fiber Metal Laminate (FML):

Fiber Metal Laminate (FML) is one of a class of metallic materials consisting of a laminate of

several thin metal layers bonded with layers of composite material.

Taking advantage of the hybrid nature from their two key constituent’s metals (mostly

aluminum) and fiber-reinforced laminate these composites offer several advantages such as

better damage tolerance to fatigue crack growth and impact damage especially for aircraft

applications. Metallic layers and fiber reinforced laminate can be bonded by classical techniques

i.e. mechanically and adhesively [22].

Figure 23: fiber metal laminate (FML’s)

Adhesively bonded fiber metal laminates have been shown to be far more fatigue resistant than

equivalent mechanically bonded structures.

Advantages:

1. Metal fatigue

2. Impact

3. Corrosion resistance

4. Fire resistance

5. Weight-savings

6. Specialized strength properties.

Fiber metal laminates are hybrid composite materials built up from interlacing layers of thin

metals and fiber reinforced adhesives.

2.7. Classification of FML’s:

The most commercially available fiber metal laminates (FMLs) are following [23]

1. ARALL (Aramid Reinforced Aluminum Laminate) based on aramid fibers

2. GLARE (Glass Reinforced Aluminum Laminate) based on high strength glass fibers

3. CARALL (Carbon Reinforced Aluminum Laminate) based on carbon fibers.

Figure 24: Classification of FML’s

1. ARALL:

ARALL is an “ARALL Reinforced Aluminum Laminate” FML Composite produced by

adhesively bonding sheets of isotropic high-strength aluminum and tough aramid fibers. The

aluminum provides higher strength isotropic properties and metal-forming qualities to the

composite laminate while the aramid fiber supplies fatigue and fracture resistance.

Figure 25: ARALL [24]

2. CARALL:

CARALL is a “Carbon Reinforced Aluminum Laminate “FML composed of several very thin

layers of metal interspersed with layers of carbon fiber bonded together with a matrix such as

epoxy. The uni-directional prepreg layers may be aligned in different Recent research has shown

that CARALL laminates also have fiber failure occurred during flight-simulation fatigue tests at

elevated stress levels which resulted in poor fatigue performance.

Figure 26: CARALL [25]

The limited failure strain of the carbon fibers (0.5–2.0) % was thought to be a disadvantage.

Thus, it is sensitive to notch behavior comparing to monolithic aluminum alloy. Due to the

problem of galvanic corrosion between the carbon fibers and the aluminum sheet in moisture

environment, more research has to be done.

3 GLARE:

GLARE is a "Glass Laminate Aluminum Reinforced Epoxy" FML composed of several very

thin layers of metal interspersed with layers of glass-fiber bonded together with a matrix such as

epoxy. The uni-directional prepreg layers may be aligned in different directions to suit the

predicted stress conditions.

Figure 27: GLARE [26]

Although GLARE is a composite material its material properties and fabrication are very similar

to bulk aluminum metal sheets. It has far less in common with composite structures when it

comes to design manufacture inspection or maintenance. GLARE parts are constructed and

repaired using mostly conventional metal material techniques.

Its major advantages over conventional aluminums are:

1. Better "damage tolerance" behavior.

2. Better corrosion resistance

3. Better fire resistance

4. Lower specific weight

characteriztion of arall comp

Documents

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arall dont

hybrid composite1

specimens of arall composite1

new class of hybrid

metal matrix composite3

polymeric materials

constituent materials