问题 问答题 简答题

复合材料为何具有可设计性?简述复合材料设计的意义。如何设计防腐蚀(碱性)玻璃纤维增强塑料?

答案

参考答案:

组分的选择、各组分的含量及分布设计、复合方式和程度、工艺方法和工艺条件的控制等均影响复合材料的性能,赋予了复合材料性能的可设计性。

意义:①每种组分只贡献自己的优点,避开自己的缺点。②由一组分的优点补偿另一组分的缺点,做到性能互补。③使复合材料获得一种新的、优于各组分的性能(叠加效应)。优胜劣汰、性能互补、推陈出新。

耐碱玻璃纤维增强塑料的设计:使用无碱玻璃纤维和耐碱性树脂(胺固化环氧树脂)。在保证必要的力学性能的前提下,尽量减少玻璃纤维的体积比例,并使树脂基体尽量保护纤维不受介质的侵蚀。

单项选择题


An adult giraffe’s head is about six feet above its heart. This means that to (67) enough blood up to the brain the circulatory (68) must be p enough to keep the blood at very high pressure.
Biologists have known for some time that giraffes solve this problem by having (69) high blood pressure, about (70) that of human beings. But an international team of biologists began to (71) about this. If giraffes have such high blood pressure, they should have a (72) problem with swelling in their legs and feet. Why don’t giraffes have swollen feet
Giraffes should have (73) problem, too. Every time they bend heads (74) to drink, the blood should (75) to their heads and have a hard time (76) back up (when the head is down) to the heart. How come giraffes don’t black out when they drink
The answer to the (77) feet problem, the researchers found, is that giraffes have (78) the researchers call a "natural anti-gravity suit". It (79) out that the skin and other (80) in their legs and feet are (81) stiffer and tougher than those of other (82) . As a result, the blood vessels in the leg cannot swell.
Therefore, the blood has nowhere to go but back to the heart. What about blood rushing to the head (83) the giraffe bends down to drink The researchers found that the giraffe’s jugular vein, which (84) blood from the head back to the heart, has lots of one-way valves in it. In the giraffe’s neck, there are lots of muscles that flex and relax repeatedly as the animal moves its head and sucks (85) drinking water. By squeezing the valved jugular vein, they (86) blood moving back to the heart even while the animal is drinking.

A.what

B.where

C.that

D.those

单项选择题 A1/A2型题