Composites are materials formed from two or more constituent materials that remain separate and distinct within a composite. Composites consist of a continuous matrix phase that surrounds and binds together a dispersed reinforcement phase. This gives composites properties that are superior to the individual components, such as high strength and stiffness. Composites can be classified based on the type of reinforcement, such as particle, structural, or fiber reinforcement composites which use particles, sheets, or fibers respectively to enhance the properties of the matrix material.

2. Definition:-
Substances that are formed by the combination of two or
more materials having different physical and chemical
properties is what is called a composite.
•Constituents remain separate and distinct, but at the
same time work together to give the composite
properties.
•They do not dissolve or blend into each other.
Hence composites are engineered materials that satisfy
the requirement of modern technology, as they have
several advantageous features like high specific strength,
high specific modulus and other desired properties.

3. CONSTITUENTS OF COMPOSITES
Composites consists minimum of two parts, a bulk or a
continuous phase called matrix and dispersed phase called the
reinforcement.
MATRIX:-
1. Surrounds the individual reinforcing elements protecting
against surface damage.
2. It maintains their relative positions.
3. Prevents the propagation of brittle cracks between individual
reinforcing elements .
e.g-thermoplastic and thermo setting polymers, metal, carbon
etc.
REINFORCEMENT:-
It imparts special electrical and mechanical properties to
enhance the matrix properties.
e.g-gravel, ceramics etc.

4. CLASSIFICATION OF COMPOSITES
1. Particle Reinforcement composites.
2. Structural Composites.
3. Fiber Reinforcement composites.
i. Continuous fibers with unidirectional aligned.
ii. Discontinuous fiber and unidirectional aligned.
iii. Discontinuous fiber and randomly oriented.

5. PARTICLE REINFORCED COMPOSITE
These are the cheapest and most widely used.
They fall in two categories depending on the size of the
particles:-
1. Large-Particle Composites
Consist of a high volume fraction of large sized hard particles
embedded in a relatively soft matrix. e.g- concrete, ceramics,
filled polymers etc.
2. Dispersion-Strengthened Composites
Contains extremely small sized particles dispersed in the
matrix at low concentration which increases the particle
matrix attractions at the atomic level thereby enhancing the
strength of the matrix against deformation. e.g- TDNickel
with 3% of Thoria.