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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
Department “ORGANIC CHEMISRTY AND TECHNOLOGY”
1. Definition
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.
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Example: concrete is a mixture of cement and aggregate, giving a robust, strong material.
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
2. Constituents of the Composite Materials
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2.1. Main Constituents of Composite MaterialThe 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.
MatrixMatrix
Reinforcemet
Interface
For the composite to operate effectively, the phases must bond where they join at the interface:
2. Constituents of the Composite Materials
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.
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2. Constituents of the Composite Materials
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.
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2. Constituents of the Composite Materials
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.
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2. Constituents of the Composite Materials
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.
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3. Classification of the Composite Materials
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.
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3. Classification of the Composite Materials
According to the type of reinforcing agents the composites can be classified:
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THANK YOU
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