【正文】 using reinforced posite structures. 聚合材料具有一些重要特性，包括尺寸(或分子量)、軟化及熔化點(diǎn)、結(jié)晶度和結(jié)構(gòu)。微粒加強(qiáng)型復(fù)合材料的一個例子是機(jī)動車胎，它就是在聚異丁烯人造橡膠聚合物基材中加入了碳黑微粒。 Fibers have a very high modulus along their axis, but have a low modulus perpendicular to their axis. Fiber posite manufacturers often rotate layers of fibers to avoid directional variations in the modulus. 纖維在沿著其軸向有很高的模量，但垂直于其軸向的模量卻較低。The strong covalent bonds along the fiber’s length give them a very high modulus in this direction because to break or extend the fiber the bonds must also be broken or moved.沿著纖維長度有很強(qiáng)結(jié)合力的共價(jià)結(jié)合在這個方向上給予復(fù)合材料很高的模量，因?yàn)橐獡p壞或拉伸纖維就必須破壞或移除這種結(jié)合。For example: polymer/ceramic posites have a greater modulus than the polymer ponent, but aren’t as brittle as ceramics. Two types of posites are: fiberreinforced posites and particlereinforced posites.例如：聚合物/陶瓷復(fù)合材料具有比聚合物成分更大的模量，但又不像陶瓷那樣易碎。The total internal reflection phenomenon, as well as the high purity of the core glass, enables light to travel long distances with little loss of intensity.全內(nèi)反射現(xiàn)象與核心玻璃的高純度一樣，使光線幾乎無強(qiáng)度損耗傳遞長距離成為可能。在這樣的溫度下，粉末內(nèi)部起反應(yīng)去除孔隙并得到十分致密的物品。因?yàn)榇蠖鄶?shù)陶瓷在從液態(tài)冷卻時將會完全破碎(即形成粉末)。 and a few special ceramics are superconductors at very low temperatures. Ceramics and glasses have one major drawback: they are brittle.許多陶瓷都是電和熱的良絕緣體。這種材料被稱為非結(jié)晶質(zhì)材料。? Ceramics and Glasses陶瓷和玻璃 A ceramic is often broadly defined as any inorganic nonmetallic material． By this definition, ceramic materials would also include glasses。 Alloys are pounds consisting of more than one metal. Adding other metals can affect the density, strength, fracture toughness, plastic deformation, electrical conductivity and environmental degradation. 合金是由一種以上金屬組成的混合物。在金屬內(nèi)部，原子的外層階電子由所有原子共享并能到處自由移動。沒有人愿意一陣強(qiáng)烈的西風(fēng)過后自己的汽車向東傾斜。金屬一般能在有缺口和凹痕的情況下不顯著削弱，并且能抵抗沖擊。大多數(shù)金屬密度相對較高，尤其是和聚合物相比較而言。 Why are metals and alloys used? Many metals and alloys have high densities and are used in applications which require a high masstovolume ratio. 為什么要使用金屬和合金？許多金屬和合金具有高密度，因此被用在需要較高質(zhì)量體積比的場合。Alloys contain more than one metallic element. Their properties can be changed by changing the elements present in the alloy. Examples of metal alloys include stainless steel which is an alloy of iron, nickel, and chromium。Some metals, such as iron, cobalt and nickel, are magnetic. At low temperatures, some metals and intermetallic pounds bee superconductors.某些金屬能被磁化，例如鐵、鈷和鎳。Nonengineering materials are the chemicals, fuels, lubricants, and other materials used in the manufacturing process, which do not bee part of the product.非工程材料則是化學(xué)品、燃料、潤滑劑以及其它用于加工制造過程但不成為產(chǎn)品組成部分的材料。科學(xué)家常根據(jù)狀態(tài)將材料分為：固體、液體或氣體。他們也把材料分為有機(jī)材料(曾經(jīng)有生命的)和無機(jī)材料(從未有生命的)。 Engineering materials may be further subdivided into: ①M(fèi)etal ②Ceramics ③Composite ④Polymers, etc. 工程材料還能進(jìn)一步細(xì)分為：①金屬材料②陶瓷材料③復(fù)合材料 ④聚合材料，等等。在極低的溫度下，某些金屬和金屬化合物能轉(zhuǎn)變成超導(dǎo)體。 and gold jewelry which usually contains an alloy of gold and nickel.合金包含不止一種金屬元素。Some metal alloys, such as those based on aluminum, have low densities and are used in aerospace applications for fuel economy. Many alloys also have high fracture toughness, which means they can withstand impact and are durable.某些金屬合金，例如鋁基合金，其密度低，可用于航空航天以節(jié)約燃料。Materials with high densities often contain atoms with high atomic numbers, such as gold or lead. However, some metals such as aluminum or magnesium have low densities, and are used in applications that require other metallic properties but also require low weight.高密度材料通常由較大原子序數(shù)原子構(gòu)成，例如金和鉛。橄欖球運(yùn)動員據(jù)此相信他的面罩不會裂成碎片。However, sometimes we can take advantage of plastic deformation. The crumple zones in a car absorb energy by undergoing plastic deformation before they break.然而，有時我們也能利用塑性變形。由于電子能導(dǎo)熱和導(dǎo)電，所以用金屬可以制造好的烹飪鍋和電線。加一些其它金屬能影響密度、強(qiáng)度、斷裂韌性、塑性變形、導(dǎo)電性以及環(huán)境侵蝕。 however, many materials scientists add the stipulation that “ceramic” must also be crystalline. 陶瓷通常被概括地定義為無機(jī)的非金屬材料。Properties of Ceramics and Glasses Some of the useful properties of ceramics and glasses include high melting temperature, low density, high strength, stiffness, hardness, wear resistance, and corrosion resistance.陶瓷和玻璃的特性 高熔點(diǎn)、低密度、高強(qiáng)度、高剛度、高硬度、高耐磨性和抗腐蝕性是陶瓷和玻璃的一些有用特性。某些陶瓷還具有一些特殊性能：有些是磁性材料，有些是壓電材料，還有些特殊陶瓷在極低溫度下是超導(dǎo)體。Hence, all the simple and efficient manufacturing techniques used for glass production such as casting and blowing, which involve the molten state, cannot be used for the production of crystalline ceramics. Instead, “sintering” or “firing” is the process typically used. 因此，所有用于玻璃生產(chǎn)的簡單有效的—諸如澆鑄和吹制這些涉及熔化的技術(shù)都不能用于由晶體物組成的陶瓷的生產(chǎn)。 An optical fiber contains three layers: a core made of highly pure glass with a high refractive index for the light to travel, a middle layer of glass with a lower refractive index known as the cladding which protects the core glass from scratches and other surface imperfections, and an out polymer jacket to protect the fiber from damage. 光導(dǎo)纖維有三層：核心由高折射指數(shù)高純光傳輸玻璃制成，中間層為低折射指數(shù)玻璃，是保護(hù)核心玻璃表面不被擦傷和完整性不被破壞的所謂覆層，外層是聚合物護(hù)套，用于保護(hù)光導(dǎo)纖維不受損。? Composites 復(fù)合材料 Composites are formed from two or more types of materials. Examples include polymer/ceramic and metal/ceramic posites. Composites are used because overall properties of the posites are superior to those of the individual ponents. 復(fù)合材料由兩種或更多材料構(gòu)成。 復(fù)合材料有兩種：纖維加強(qiáng)型復(fù)合材料和微粒加強(qiáng)型復(fù)合材料。 Fibers are difficult to process into posites, making fiberreinforced posites relatively expensive. 把纖維放入復(fù)合材料較困難，這使得制造纖維加強(qiáng)型復(fù)合材料相對昂貴。纖維復(fù)合材料的制造者往往旋轉(zhuǎn)纖維層以防模量產(chǎn)生方向變化。? Polymers 聚合材料 A polymer has a repeating structure, usually based on a carbon backbone. The repeating structure results in large chainlike molecules. Polymers are useful because they are lightweight, corrosion resistant, easy to process at low temperatures and generally inexpensive. 聚合物具有一般是基于碳鏈的重復(fù)結(jié)構(gòu)。聚合材料的機(jī)械性能一般表現(xiàn)為低強(qiáng)度和高韌性。 Thermal transitions. The softening point (glass transition temperature) and the melting point of a polymer will determine whic