Composites are materials formed from
a mixture of two or more components which, when combined, produce
a material with properties or characteristics which are superior
to those of the individual materials. Most composites are comprised
of two parts, namely the polymer matrix component and the reinforcement
component(s). The polymer matrix components are the materials which
encapsulate the reinforcing material. The resulting matrix with
reinforcements in place and distributing the load among the reinforcements.
Since reinforcements are usually stiffer than the matrix material,
they are the primary load-carrying component within the composite.
Reinforcements may come in many different forms ranging from fibers,
to fabrics, to particles imbedded into the matrix that form the
Composite structures have existed for millions of years in nature.
Wood is a wonderful example. Examination of the microstructure of
wood reveals the composites material found in nature and suggests
that modern composite materials have essentially evolved mimicking
structures found in nature. A prefect example of a composite would
be concrete. If you look at the different forms of concrete you
will quickly get the idea of how reinforcements work. The cement
acts as the matrix, which holds the concrete together, while the
sand, gravel, and steel, serve as reinforcements. Concrete made
with only sand and cement isn't nearly as strong as concrete made
from cement, sand, gravel, which, in turn, is not as strong as concrete
reinforced with steel, sand and gravel. The matrix and reinforcement
materials of concrete are blended, poured and molded, typically
in a form structure. In the generation of parts made with other
composite materials, the shape of a composite part is determined
by the shape or geometry of the mold, die of other tooling used
in the part forming.
|There are many different types of composites,
including plastic composites. Each plastic resin has its own
unique properties, which when combined with different reinforcements
create composites with differing mechanical and physical properties.
If one considered the number of plastic polymers in existence
today and multiplied that figure by the number of reinforcements
available, the number of potential composite materials is staggering.
Of all the available plastic composites, there are two primary
categories: Thermoset and Thermoplastic composites.
In the case of Thermoset composites, after application of heat
and pressure, Thermoset resins undergo a chemical change, which
cross-links the molecular structure of the material. Once cured,
a Thermoset part cannot be remolded.
Thermoplastic materials are not as constrained
as Thermoset materials and can be recycled and reshaped to
create a new part. Thermoplastics that are reinforced with
high-strength, high-modulus fibers provide dramatic increases
in strength and stiffness, as well as toughness and dimensional
stability. The performance gain achieved from Thermoplastic
materials is often justification that compensates for the
increased costs of most Thermoplastic materials.
Composite materials are used in numerous applications across a
broad range of industries. Typically, composites are used to replace
products made of metal alloys. Composites can offer comparable or
better strength than metal parts, while providing a reduction in
weight. This is particularly important in industries such as automotive
and aerospace, where the use of composite materials results in lighter,
faster and more fuel-efficient aircraft and automobiles.
Thermoplastic composites may also be designed to replace wood,
fiberglass, concrete and other more traditional materials. The following
is a partial list of industries that may have application for the
use of long-fiber reinforced structural parts made from thermoplastic
||In general, among other attributes, composite
materials are corrosion resistant and offer long fatigue lives,
which has made them particularly attractive for many manufacturers.
The fatigue life refers to the period of time the part will
last prior to exhibiting material wear or significant stress.
Typically, composites are substituted for conventional materials
where there is a desire to reduce the weight of a particular
part while providing the required strength and other performance
Numerous parts, particularly in the aerospace industry, have been
and are being made from "advanced" thermoset composite
materials, which are very expensive. These types of advanced composite
parts are typically in the military and aerospace industries.
As a result of the previously noted issues and due to advances
in thermoplastic composites, many product development engineers
and design engineers believe that composite materials will play
an ever-increasing role in modern technological development. New
thermoplastic resins are regularly developed and more innovative
methods of manufacturing are being introduced bringing down the
costs of manufacturing parts. As costs for reinforced thermoplastic
production are lowered, the use of thermoplastics composites becomes
more and more viable in many commercial and industrial applications.