Exercise 6. Read the text “Composite Materials” and fill the gaps with the following words or phrases: volumes/ conductivity/ properties/ composite/ high/ combinations/
The 1) of two or more different materials are called composite materials. They usually have unique mechanical and physical properties because they combine the best
2) of different materials. Nowadays composites are being used for structures such as bridges, boat-building etc.
Composite materials usually consist of synthetic fibres within a matrix, a material that surrounds and is tightly bound to the fibres. The most widely used type of 3) material is polymer matrix composites (PMCs). PMCs consist of fibres made of a ceramic material such as carbon or glass embedded in a plastic matrix. Usually the fibres make up about 60 per cent by volume.
Composites can also have different properties, such as high thermal or electrical 4) and a low coefficient of thermal expansion.
Although composite materials have certain advantages over conventional materials, composites also have some disadvantages. For example, PMCs and other composite materials tend to be highly anisotropic— that is, their strength, rigidness, and other engineering properties are different depending on the orientation of the composite material. The designer who uses composite materials in structures subjected to multidirectional forces, must take these anisotropic properties into account. Also, forming strong connections between separate composite material components is difficult.
The advanced composites have 5) manufacturing costs. Fabricating composite materials is a complex process. However, new manufacturing techniques are developed. It will become possible to produce composite materials at higher 6) and at a lower cost than is now possible, accelerating the wider exploitation of these materials.