Design and Synthesis of Advanced Composites for Cryogenic Uses

本研究的目的是为设计和合成可在低温环境中使用的高级复合材料积累基础信息。从第一年的实验结果来看，能够改变主链键角的聚合物似乎在低温性能方面表现优异。部分原因是，即使在低温下冻结了它们的片段运动，这些聚合物也会发生变形，因此通过改变主链键角仍然可以保持柔性。在第二年的实验中，研究了聚合物的结晶度与低温性能之间的关系。聚苯硫醚在77 K时的强度和断裂伸长率随结晶度的增加而增加，而聚萘二甲酸乙二醇酯在77 K时的强度和断裂伸长率随结晶度的增加而降低。这些结果表明，聚合物的形态对其低温性能有很大影响。聚合物复合材料的一些性能取决于许多因素，如树脂含量、基体体系的相对柔韧性、固化温度和压力、固化和后固化周期，以及纤维的表面处理。这些发现为开发新型先进的低温复合材料提供了有益的信息。

The purpose of this study is to accumulate the fundamental information for design and synthesis of advanced composites usable in cryogenic environments, From the results obtained in experiments of the first year, it is suggested that the polymers which are able to change the bond angles of the main chain seem to excel in cryogenic properties. This is partly because, even when their segmental motions are frozen out at cryogenic temperatures, these polymers could undergo deformation, and hence could still be flexible by changing the mainchain bond angles. In the experiments of the second year, the relationship between the crystallinity of polymers and the cryogenic properties was studied. The strength and the elongation at break point of polyphenylene sulfide at 77 K increase with an increase in the degree of crystallinity, In the case of polyethylene naphthalate, however, both mechanical properties at 77 K decrease with increasing the degree of crystallinity. These results indicate that the morphology of polymers greatly affects their cryogenic properties. Several properties of polymer composites are dependent on large number of factors such as resin content, relative flexibility of the matrix system, curing temperature and pressure, cure and post-cure cycle, as well as surface treatment of fibers. These findings offer us the useful information for developing the new type of advanced composites for cryogenic applications.