What Are Plastic Composite Materials?

An increasing number of manufacturers are discovering the benefits of composite plastic materials. They are used extensively in a range of products, from consumer and medical applications to transport and aerospace structures. Science and technology have helped industries combine and improve these versatile materials to create lighter, stronger and more flexible structures and products.
Definition
Although there are many kinds of composites both natural and manmade, commonly the term refers specifically to reinforced plastics and polymers.
A plastic composite is a combination of two materials: a matrix, or resin solution, and a reinforcement. The polymer matrix surrounds and binds the reinforcement, which is a cluster of fibers or fragments of a much stronger material. These two components have different attributes, but together they give the composite unique properties otherwise unavailable from the individual materials.
Polymer and Plastic Composites
The most common polymer and plastic composites include: fiber-reinforced plastics (FRPs); sheet molding compounds (SMCs); bulk molding compounds (BMCs); prepreg materials; and fabricated composite parts.
The most popular composites are FRPs that incorporate a structural fiber and a plastic. The fiber ensures the composite has structure and strength, while the plastic polymer holds the fibers together.
The Matrix
There are several categories of plastic resins for the matrix available on the market, depending on the raw ingredients in their composition. The most common kinds include: polyester, vinyl ester, epoxy, phenolic, polyimide, polyamide, polypropylene and PEEK.
Resins are available as compounds, liquids, pellets and powders. They not only hold the reinforcement together, but also protect the fibers from damage by sharing the stress among them. Resins determine the physical properties of the end products.
The matrix is soft enough to allow tool shaping. If damaged, manufacturers can repair it by softening with certain solvents.
Reinforcement
The reinforcement materials -- usually fibers and ground minerals -- have special mechanical and physical attributes that enhance the matrix properties. Common types of fibers used in FRP composites include: fiberglass, carbon fiber, aramid fiber, boron fiber, basalt fiber and natural fiber such as wood, flax or hemp.
While glass fibers are the most common, many advanced composites use pure carbon fine fibers. These are much stronger than glass fibers, but also more costly to produce. They usually go into aircraft structures and sporting goods. In the medical world, they serve as bone repair and replacement material where metal would have been used in the past.
Benefits of Composites
Composites often provide an advantage compared to materials such as metal and wood. They are strong and lightweight, which makes them ideal for use in the aviation, medical and sporting goods industries. Composites go into whole sections of a plane, such as wings, tails, propellers and most of the internal structure and fittings. The material helps improve flying speed and is less likely to break up under stress. While a small crack in a piece of metal can spread rapidly, the fibers in a composite block are better able to handle stress.
Composites are durable materials, widely used in products such as boats, chemical-handling equipment and spacecraft, which are exposed to extreme environments, from high heat to corrosion.
Last, but not least, the plastic composites allow for an impressive design flexibility and manufacturers can mold them into complex shapes useful for certain end products such as a tennis racket or a gold shaft.