Transcript Раздел VI Методи, процеси и съоръжения за

Department “ORGANIC CHEMISRTY AND TECHNOLOGY”
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Chemistry for Engineering Logistics
COMPOSITE MATERIALS
1. Definition
2. Constituents of the Composite Materials
3. Classification of the Composite Materials
Assoc. Pref. V. Grozev
1. Definition
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Composites are materials made from two or more constituent
materials with different physical and chemical properties, that when
combined, produce a material with characteristics different from the
individual components.
The individual components
remain separate and distinct
within the finished structure. The
new material may be preferred for
many
reasons:
common
examples include materials which
are stronger, lighter or less
expensive when compared to
traditional materials
Example: concrete is a mixture of
cement and aggregate, giving a robust,
strong material.
2. Constituents of the Composite Materials
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2.1. Main Constituents of Composite Material
The main constituents of composites are the matrix and the
reinforcement materials.
The matrix forms the volume of the composite material within which
the reinforcing agent is imbedded. The matrix fit together all parts of the
composite, while the reinforcements usually serve to strengthen the
composite.
For the composite
to operate effectively,
the phases must bond
where they join at the
interface:
Matrix
Matrix
Reinforcemet
Interface
2. Constituents of the Composite Materials
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2.2. Functions of the matrix
The matrix material can be polymer, metal or other unorganic
substance.
The Matrix Material:
 Provides the bulk form of the part or product made of the composite
material;
 Holds the imbedded phase in place, usually enclosing and often
concealing it;
 When a load is applied, the matrix shares the load with the
secondary phase, in some cases deforming so that the stress is
essentially born by the reinforcing agent.
2. Constituents of the Composite Materials
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2.3. Reinforcing agents
Function is to reinforce the matrix.
Shape of Reinforcements
Reinforcing agents are most commonly one of the following shapes:

Fibers (a);

Particles (b);

Flakes (c)

Textile materials, sheet of pater, folios.
2. Constituents of the Composite Materials
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Materials for Fibers
Fiber materials in fiber-reinforced composites:

Glass – most widely used filament;

Carbon – high elastic modulus;

Boron – very high elastic modulus;

Polymers – Kevlar;

Ceramics – SiC and Al2O3

Metals – steel.
The most important commercial use of fibers is in polymer
composites.
2. Constituents of the Composite Materials
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Particles and Flakes
A second common shape of imbedded phase are particles ,
ranging in size from microscopic to macroscopic.
Flakes are basically two-dimensional particles - small flat platelets
The distribution of particles in the composite matrix is random, and
therefore strength and other properties of the composite material are
usually isotropic.
Strengthening mechanism depends on particle size.
3. Classification of the Composite Materials
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After the kind of the matrix composites can be devided into
three groups:

Metal Matrix Composites (MMCs) - mixtures of ceramics and
metals, such as cemented carbides and other cermets;

Ceramic Matrix Composites (CMCs) - Al2O3 and SiC imbedded
with fibers to improve properties, especially in high temperature
applications;

Polymer Matrix Composites (PMCs) - thermosetting resins are
widely used in PMCs. Examples: epoxy and polyester with fiber
reinforcement, and phenolic with powders.
3. Classification of the Composite Materials
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According to the type of reinforcing agents the composites can
be classified:
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