introduction composite and nanocomposite materials part-i prepared by_s. manish rtdc

Introduction

Composite and

Nanocomposite Materials

Part-I

Prepared By_S. Manish RTDC

MATERIALS

Materials are special solids which can be tailored to develop desired properties applied for fabrication of devices leading to societal benefits


Historically development and advancement of societies have been intimately related to materials and its development. There were stone age, bronze age, etc.

Naturally occurring materials are stone, wood, clay, skin, etc.

With time, techniques were discovered for producing materials that had properties superior to naturally occurring materials. Potteries and metals were some of the examples.

Further it was discovered that heat treatment or addition of one material into other changed the properties of materials.

However in ancient times people did not know the science of materials and hence could develop only few materials for their daily use.


With the advancement of science, structure-property correlation of materials could be understood and a new discipline of science known as Materials science emerged.

With the advancement of science, structure-property correlation of materials could be understood and a new discipline of science known as Materials science emerged.

The development of many technologies that make our life comfortable is closely related to materials.

The discipline of materials science involves investigating the relationships that exist between structures and properties

Materials engineering is, on the basis of structure-property correlations, designing or engineering the structure of a material to produce a predetermined set of properties

Materials, Materials Science and Materials Scientist play a very vital role in the development of a country.

Properties of materials are size dependent

Materials scientist claim that 21st century is the century of materials and especially nanomaterials.


CLASSIFICATION OF MATERIALS

Solid materials have conveniently been grouped into

three classes

Combination of above materials give variety of other Materials.


CeramicsCeramics PolymersPolymersMetalsMetals

Now most of the new materials come under the category of Advanced Materials

or Future Materials

THREE MAJOR ENGINEERING MATERIALSPrepared By_S. Manish RTDC

Many of our modern technologies require materials with unusual combinations of properties that can not be met by the conventional metal alloys, ceramics and polymeric materials.

This is usually true for materials that are needed for aerospace, underwater, and transportation applications.

For example aircraft engineers are increasingly searching for structural materials that have low densities, are strong, stiff and abrasion and impact resistant, and are not easily corroded.

This is a formidable combination of characteristics.

Frequently strong materials are relatively dense; also, increasing the strength or stiffness generally results in a decrease in impact resistance.


Material property combinations and ranges have been and are yet being extended by the development of composite materials.

According to this principle of combined action, better property combinations are fashioned by the careful combination of two or more distinct materials

Composites


Generally speaking, a composite is considered to be any multiphase material that exhibits a important amount of the properties of both components (materials) such that a improved combination of properties is realized.

Generally speaking, a composite is considered to be any multiphase material that exhibits a important amount of the properties of both components (materials) such that a improved combination of properties is realized.

In the present context,

A composite is a multiphase material that is artificially made, as opposed to one that occurs or forms naturally.


In addition, the constituent phases must be chemically dissimilar and separated by a distinct interface.

Thus most metallic alloys and many ceramics do not fit this definition because their multiple phases are formed as a consequence of natural phenomena.

• Composites are a combination of two or more organic or inorganic components one of which serves as a matrix holding the materials together and then other of which serves as reinforcement in the form of fibers

• Two inherently different materials that when combined together produce a material with properties that exceed the constituent materials.

• Composites are lightweight and strong but they are complex to manufacture, expensive and hard to inspect for flaws


Many composite materials are composed of just two phases; one is termed the matrix, which is continuous and surrounds the other phase, often called dispersed phase.

The properties of composites are a function of the properties of the constituent phases, their relative amounts and the geometry of the dispersed phase.

Dispersed phase geometry in this context means the shape of the particles and the particle size, distribution and orientation.


Composites often have only two phases• Matrix phase

– continuous - surrounds other phase

• Dispersed phase– discontinuous phase

Matrix (light)Dispersed phase (dark)


Classification of Artificial Composites

Composites

Particulate Fiber Structural

ContinuousDiscontinuous

Laminates SandwichPanels

LargeParticle

DispersionStrengthened

Aligned Random


Properties of Composites

Properties depend on:constituent phases

relative amounts

geometry of dispersed phase

shape of particles

particle size

particle distribution

particle orientation

For a given matrix/dispersed phase

system:

Concentration

Size

Shape

Distribution

Orientation


Parameters on which properties dependParameters on which properties depend

Concentration

SizeShape

Distribution Orientation


Composites Offer

High Strength

Light Weight

Design Flexibility

Consolidation of Parts

Net Shape Manufacturing


Biocomposites• Biocomposites combine plant fibers with resins to create

natural based composite materials.

• High tensile plant fibers including, kenaf, industrial hemp, and flax, can be combined with traditional resins to create an alternative to traditionally steel or fiberglass applications.

• Some advantages over traditional composites: – Reduced weight – Increased flexibility – Greater moldability – Less expensive – Sound insulation – Renewable resource – Self-healing properties


Fiber-Reinforced Composites

• Technologically, the most important type of composite.

• Characterized in terms of specific strength or specific modulus = strength (or E) per weight– usually want to maximize

specific strength and modulus

• Subclasses:– Short fiber and continuous

fiber lengths

Fiber PhaseRequirements for the fiber• The small diameter fiber must be much stronger than

the bulk material• High tensile strength (Wiskers, Fibres, Wires)

Matrix PhaseFunction• Binds fibers together• Acts as a medium through which externally

applied stress is transmitted and distributed to the fibers

• Protects fiber from surface damage• Separates fibers and prevents a crack from one

fiber from propagating through another


Influence of Fiber Orientation

• Fiber parameters– arrangement with respect

to each other– distribution– concentration

• Fiber orientation– parallel to each other– totally random– some combination


Limitations of Composites– Properties of material are highly anisotropic due to orientation

fibers– Modulus in direction of alignment is a function of the volume

fraction of the E of the fiber and matrix– Modulus perpendicular to direction of alignment is considerably less

(the fibers do not contribute)– Loss of transparency– Loss Optical/Electrical/Chemical (barrier) Properties



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introduction composite and nanocomposite materials part-i prepared by_s. manish rtdc

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