AP1200_Ch8_Materials-2008 - AP1200 Foundation Physics...

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AP1200 Foundation Physics Chapter 8: Materials In this Chapter we will introduce materials science and engineering. 8.1 Historical view Materials are everywhere around us: nature has produced stone, metals, sand, mud, as well as many kinds of highly specialized biological materials, from wood and bone to muscles, skin, light detectors, nerves and brain; humans use many different materials to make walls, windows, furniture, lamps, pipes, instruments, computers, telephones, PDAs, pens, clothes, health products, pharmaceuticals, bottles, bags, machines, vehicles, etc. Every object that we see is made of some material or, more frequently, of a combination of different materials. Civilization depends on materials : human history can be divided into the Stone Age , the Bronze Age , the Iron Age , the Steam Age , and perhaps the Oil Age , the Plastic Age , the Silicon Age and the Carbon Age , reflecting the central role taken by materials. Fig. 8.1 shows the interesting evolution of the human use of materials through different stages of civilization. Until about 2000 years ago, mankind relied primarily on ceramics (stone, pottery) and a few glasses, as well as on natural materials like wood, skins and fibers. A few composite materials were also developed, such as straw and bricks mixed for stronger house construction, and paper made from fibers for writing. Fig . 8.1 Materials through the ages The metals gold and copper were used early in civilization, because they could be found “ready made” in nature, but they are too soft for many applications. Bronze was the first metal to be prepared by man, by combining copper with other metals. It was stronger and so 1
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it could be used in tools, weapons, armour, and various building materials. Bronze was followed by iron and then steel, a stronger derivative of iron. The strength of steel made new constructions possible, such as large bridges, tall buildings and powerful machines. Metals became by far the dominant material used in advanced societies until the middle of the 20th century. Steam and oil had immense impacts on human power and mobility, and their use was made possible in great part by the availability of iron and steel that could resist the high temperatures and forces involved with using steam and oil. In the last half-century, new polymers (plastics) became increasingly popular, thanks to their light weight, high flexibility and relative strength, as well as to the availability of oil to make them. In the second half of the 20th century, composites also made a comeback: they combine individual materials into new materials that bring together useful properties of the individual materials. Composites are attractive when no single material provides all the needed properties. An important example is polymer-matrix composites: for instance, glass fibers are included in a polymer to add strength while maintaining some of the polymer’s desirable properties, such as light weight and flexibility; the polymer alone would not provide the desired strength, while glass fibers alone would be heavier and less flexible.
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AP1200_Ch8_Materials-2008 - AP1200 Foundation Physics...

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