Composite
materials (or composites for
short) are engineering
materials made from two or
more constituent materials
that remain separate and
distinct on a macroscopic
level while forming a single
component. There are two
categories of constituent
materials: matrix and
reinforcement. At least one
portion of each type is
required. The matrix
material surrounds and
supports the reinforcement
materials by maintaining
their relative positions.
The reinforcements impart
their special mechanical and
physical properties to
enhance the matrix
properties. A synergism
produces material properties
unavailable from the
individual constituent
materials, while the wide
variety of matrix and
strengthening materials
allows the designer of the
product or structure to
choose an optimum
combination.
Engineered composite
materials must be formed to
shape. The matrix material
can be introduced to the
reinforcement before or
after the reinforcement
material is placed into the
mold cavity or onto the mold
surface. The matrix material
experiences a melding event,
after which the part shape
is essentially set.
Depending upon the nature of
the matrix material, this
melding event can occur in
various ways such as
chemical polymerization or
solidification from the
melted state.
Most commercially produced
composites use a polymer
matrix material often called
a resin solution. There are
many different polymers
available depending upon the
starting raw ingredients.
There are several broad
categories, each with
numerous variations. The
most common are known as
polyester, vinyl ester,
epoxy, phenolic, polyimide,
polyamide, polypropylene,
PEEK, and others. The
reinforcement materials are
often fibers but also
commonly ground minerals.
