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  3. One of the differences between animals and machines is that animal bodies can repair much of the damage that a cruel and hostile

One of the differences between animals and machines is that animal bodies can repair much of the damage that a cruel and hostile

admin2015-04-10  31
问题     One of the differences between animals and machines is that animal bodies can repair much of the damage that a cruel and hostile world inflicts on them. A machine, by contrast, has to wait for someone to fix it. But that may change if researchers of self-repairing materials have their way. Two groups in America and Britain are trying to create composite materials that mend themselves if they get cracked, in much the same way that an animal’s broken bone heals itself. The difference is that these materials will heal in minutes rather than months.
    Such self-healing composites may take a while to enter everyday use. But if they can be made reliable they will be welcome in high-stress applications. Jeffrey Moore and his colleagues at the University of Illinois are working on the problem by adding extra components to their composites. These composites consist of fibres embedded in a plastic matrix. The main extra component added by Dr. Moore is a sprinkling of tiny capsules containing a chemical. If the composite cracks, the capsules near the crack break open and release the chemical molecules, which link together to form another type of plastic that binds the crack together and heals the material.
    Ian Bond and his colleagues at the University of Bristol’s department of aerospace engineering are taking a slightly different approach. They use glass fibres rather than carbon fibres in their composite and, instead of adding capsules, they have put the healing molecules into the fibres themselves. The molecules in question are the two ingredients of epoxy resin. Half the fibres contain one ingredient and half contain the other. A crack in the material breaks the fibres, releasing the ingredients which react, form more epoxy, and thus mend the crack. The advantage of this approach is that it retains the basic fibre-plus-matrix structure of the material. Adding capsules changes that and risks weakening it. The disadvantage is that capsules are easier to make than hollow, fluid-filled fibres.
    Whichever system is adopted, two further things are needed. One is a way of checking that a component really has healed. The other is a way to top up the healing molecules once some of them have been used. A repaired area would develop a bruise. Topping up the supply of healing fluid might be done by mimicking another biological system—the network of blood capillaries that supplies living tissues with the stuff they need to thrive. Dr. Moore and Dr. Bond are attempting to borrow from nature this way. If they succeed, the machines of the future will have longer and healthier lives.
Which of the following is true about Ian Bond’s method?
选项 A、The capsules he uses are more difficult to make than hollow fibres.
B、He uses carbon fibres rather than glass fibres in his composite materials.
C、He has added capsules into the fibres themselves instead of the healing molecules.
D、A crack in the material breaks the fibres to release the ingredients to fix the crack.
答案D
解析 下列几个有关伊恩·邦德所用方法的表述中，哪项正确?[A]他使用的胶囊比中空的纤维更难制作。[B]他在合成材料里使用的是碳纤维而不是玻璃纤维。[C]他在纤维内部加入了胶囊而不是修复分子。[D]材料出现的裂痕会破坏纤维，释放成分来修复裂痕。第三段最后一句提到，伊恩·邦德所采用方法的缺点是相比中空的、充满液体的纤维，胶囊制作起来更简便。因此[A]与文意不符。根据第三段第二句可知，[B]错误；由本段倒数第二句和第三句可知，通过有自我修复功能的分子可以使其恢复，[C]错误；由第三段第五句可知，[D]正确。
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