1. Introduction Composite and Nanocomposite Materials
Part-I
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MATERIALS
Materials are special solids which can be tailored to develop desired properties applied for fabrication of devices leading to societal benefits
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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.
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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.
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5. CLASSIFICATION OF MATERIALS
Solid materials have conveniently been grouped into
three classes
Combination of above materials give variety of other Materials.
Metals
Ceramics
Polymers
Now most of the new materials come under the category of Advanced Materials or Future Materials
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6. THREE MAJOR ENGINEERING MATERIALS
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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.
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Composites
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
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.
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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.
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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
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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.
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Composites often have only two phases
Matrix phase
continuous - surrounds other phase
Dispersed phase
discontinuous phase
Matrix (light)
Dispersed phase (dark)
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13. Classification of Artificial Composites
Particulate
Fiber
Structural
Large
Dispersion
Laminates
Sandwich
Particle
Strengthened
Panels
Continuous
Discontinuous
Aligned
Random
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14. 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
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15. Parameters on which properties depend
Concentration
Orientation
Distribution
Shape
Size
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Composites Offer
High Strength
Light Weight
Design Flexibility
Consolidation of Parts
Net Shape Manufacturing
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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
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18. 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 Phase
Requirements for the fiber
The small diameter fiber must be much stronger than the bulk material
High tensile strength
(Wiskers, Fibres, Wires)
Matrix Phase
Function
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
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19. Influence of Fiber Orientation
Fiber parameters
arrangement with respect to each other
distribution
concentration
Fiber orientation
parallel to each other
totally random
some combination
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20. 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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Thanks
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