【正文】 或拉伸纖維就必須破壞或移除這種結(jié)合。Fiberreinforced Composites Reinforcing fibers can be made of metals, ceramics, glasses, or polymers that have been turned into graphite and known as carbon fibers. Fibers increase the modulus of the matrix material. 纖維加強(qiáng)型復(fù)合材料 加強(qiáng)纖維可以是金屬、陶瓷、玻璃或是已變成石墨的被稱為碳纖維的聚合物。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。例子有聚合物/陶瓷和金屬/陶瓷復(fù)合材料。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(wú)強(qiáng)度損耗傳遞長(zhǎng)距離成為可能。In order for the core glass to have a higher refractive index than the cladding, the core glass is doped with a small, controlled amount of an impurity, or dopant, which causes light to travel slower, but does not absorb the light. 為了使核心玻璃有比覆層大的折射指數(shù)，在其中摻入微小的、可控?cái)?shù)量的能減緩光速而不會(huì)吸收光線的雜質(zhì)或攙雜劑。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。作為替代，一般采用“燒結(jié)”或“焙燒”工藝。因?yàn)榇蠖鄶?shù)陶瓷在從液態(tài)冷卻時(shí)將會(huì)完全破碎(即形成粉末)。陶瓷和玻璃都有一個(gè)主要的缺點(diǎn)：它們?nèi)菀灼扑椤?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。Many ceramics are good electrical and thermal insulators. Some ceramics have special properties: some ceramics are magnetic materials。這種材料被稱為非結(jié)晶質(zhì)材料。照此定義，陶瓷材料也應(yīng)包括玻璃；然而許多材料科學(xué)家添加了“陶瓷”必須同時(shí)是晶體物組成的約定。? 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。For example, adding a small amount of iron to aluminum will make it stronger. Also, adding some chromium to steel will slow the rusting process, but will make it more brittle.例如，往鋁里加少量鐵可使其更強(qiáng)。 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。It is impossible to see through metals, since these valence electrons absorb any photons of light which reach the metal. No photons pass through.因?yàn)檫@些階電子吸收到達(dá)金屬的光子，所以透過(guò)金屬不可能看得見(jiàn)。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(dòng)。汽車上壓皺的區(qū)域在它們斷裂前通過(guò)經(jīng)歷塑性變形來(lái)吸收能量。沒(méi)有人愿意一陣強(qiáng)烈的西風(fēng)過(guò)后自己的汽車向東傾斜。 Plastic deformation is the ability of bend or deform before breaking. As engineers, we usually design materials so that they don’t deform under normal conditions. You don’t want your car to lean to the east after a strong west wind. 塑性變形就是在斷裂前彎曲或變形的能力。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。然而，諸如鋁和鎂之類的一些金屬則具有低密度，并被用于既需要金屬特性又要求重量輕的場(chǎng)合。大多數(shù)金屬密度相對(duì)較高，尤其是和聚合物相比較而言。許多合金還具有高斷裂韌性，這意味著它們能經(jīng)得起沖擊并且是耐用的。 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(chǎng)合。合金的性質(zhì)能通過(guò)改變其中存在的元素而改變。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。 What is the difference between an alloy and a pure metal? Pure metals are elements which e from a particular area of the periodic table. Examples of pure metals include copper in electrical wires and aluminum in cooking foil and beverage cans. 合金與純金屬的區(qū)別是什么？純金屬是在元素周期表中占據(jù)特定位置的元素。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。? Metals and Metal Alloys 金屬和金屬合金 Metals are elements that generally have good electrical and thermal conductivity. Many metals have high strength, high stiffness, and have good ductility. 金屬就是通常具有良好導(dǎo)電性和導(dǎo)熱性的元素。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(rùn)滑劑以及其它用于加工制造過(guò)程但不成為產(chǎn)品組成部分的材料。 For industrial purposes, materials are divided into engineering materials or nonengineering materials. Engineering materials are those used in manufacture and bee parts of products. 就工業(yè)效用而言，材料被分為工程材料和非工程材料。科學(xué)家常根據(jù)狀態(tài)將材料分為：固體、液體或氣體。117目錄12812單元第一單元? Types of Materials 材料的類型 Materials may be grouped in several ways. Scientists often classify materials by their state: solid, liquid, or gas. They also separate them into organic (once living) and inorganic (never living) materials. 材料可以按多種方法分類。他們也把材料分為有機(jī)材料(曾經(jīng)有生命的)和無(wú)機(jī)材料(從未有生命的)。那些用于加工制造并成為產(chǎn)品組成部分的就是工程材料。 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。許多金屬具有高強(qiáng)度、高硬度以及良好的延展性。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。例如電線中的銅和制造烹飪箔及飲料罐的鋁。 and gold jewelry which usually contains an alloy of gold and nickel.合金包含不止一種金屬元素。金屬合金的例子有：不銹鋼是一種鐵、鎳、鉻的合金，以及金飾品通常含有金鎳合金。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。 What are some important properties of metals? Density is defined as a material’s mass divided by its volume. Most metals have relatively high densities, especially pared to polymers. 金屬有哪些重要特性？ 密度定義為材料的質(zhì)量與其體積之比。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。 Fracture toughness can be described as a material’s ability to avoid fracture, especially when a flaw is