Composite Material - An Introduction

By Author: Jason Paget
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A composite is a material composed of a reinforcing fiber and a resin matrix. Composites are classified according to their matrix phase (the material which surrounds the fiber). Composite products range from skateboards to components of the space shuttle. Materials within the composites industry are often called "advanced" if they combine the properties of high strength and high stiffness, low weight, corrosion resistance, and in some cases special electrical properties. Several of the manufacturing processes and potential hazards are common to both polymer matrix composites and advanced polymer matrix composites.

Composite Theory

In its most basic form a composite material is one, which is composed of at least two elements working together to produce material properties that are different to the properties of those elements on their own. In practice, most composites consist of a bulk material (the ‘matrix'), and a reinforcement of some kind, added primarily to increase the strength and stiffness of the matrix. This reinforcement is usually in fibre form. Today, the most common man-made composites ...
... can be divided into three main groups:

1) Polymer Matrix Composites (PMC's) - These are the most common and it also known as FRP - Fibre Reinforced Polymers (or Plastics) - these materials use a polymer-based resin as the matrix, and a variety of fibres such as glass, carbon and aramid as the reinforcement.

Polymer matrix composites (PMCs) are materials that use a polymer based resin as a matrix material with some form of fibres embedded in the matrix, as reinforcement. Both thermosetting and thermoplastic polymers can be used for the matrix material. Common polymer composite thermosetting matrix materials include polyester, vinyl ester and epoxy. Polymer composite thermoplastic matrix materials include PEEK, PEI and PPS. Reinforcements include glass, carbon and aramid fibres.

There can be many secondary reasons why polymer composites may be chosen for the manufacture of particular articles or components, but the primary reason is because of weight saving for their relative stiffness and strength. As an example we can compare a carbon fibre reinforced composite with its steel counterpart. The carbon fibre composite can be five times stronger than 1020 grade steel while having only one fifth the weight. Aluminium (6061 grade) is much nearer in weight to carbon fibre composite (though still somewhat heavier), but the composite can have twice the modulus and up to seven times the strength.

2) Metal Matrix Composites (MMC's) - Increasingly found in the automotive industry, these materials use a metal such as aluminium as the matrix, and reinforce it with fibres such as silicon carbide.

3) Ceramic Matrix Composites (CMC's) - Used in very high temperature environments, these materials use a ceramic as the matrix and reinforce it with short fibres, or whiskers such as those made from silicon carbide and boron nitride.

Composite materials cover a wide range of engineered materials comprising several distinct constituent materials chosen to give overall properties superior to anyone of the parts. Modern high technology composites are often used to minimize weight in applications such as aerospace, motorsport or racing yachts. To achieve the necessary design performance requires confidence in the materials as overdesign would squander the precious gains in weight.

About Author:

Jason Paget from Elite Composites writes about Composite Material. For more information on Composite Material please visit http://www.elitecomposites.co.uk/