Carbon fibers are stronger and lighter than steel, and composite materials based on carbon-fiber-reinforced polymers are being used in an expanding range of aerospace, automotive, and other applications – including major sections of the Boeing 787 aircraft.
It’s widely believed, moreover, that carbon-fiber technology has the potential to produce composites at least 10 times stronger than those in use today.
一个研究团队佐治亚理工学院已经开发了一种新颖的技术，为碳纤维的强度和模量树立了新的里程碑。这种替代方法基于一种用于旋转聚丙烯硝基硝基酯（PAN）的创新技术，这是一种有机聚合物树脂，用于制造碳纤维。
The work is part of a four-year, $9.8 million project sponsored by the Defense Advanced Research Projects Agency (DARPA) to improve the strength of carbon-fiber materials. The research was reported recently in the journalCarbon.
“通过使用凝胶旋转技术将聚丙烯硝基烯烯共聚物处理成碳纤维，我们开发了下一代碳纤维，这些碳纤维表现出强度和模量的结合，以前用常规溶液旋转方法看不到，” Satish Kumar说，”领导该项目的佐治亚理工学院材料科学与工程学院。“此外，我们的工作表明，凝胶旋转方法为更大的改进提供了途径。”
库马尔（Kumar）解释说，拉伸模量（一种刚度的度量）是指通过给定量拉伸材料所需的力。拉伸强度表示实际破坏材料需要多少力。
In gel spinning, the solution is first converted to a gel; this technique binds polymer chains together and produces robust inter-chain forces that increase tensile strength. Gel spinning also increases directional orientation of fibers, which also augments strength. By contrast, in conventional solution spinning, a process developed more than 60 years ago, PAN co-polymer solution is directly converted to a solid fiber without the intermediate gel state and produces less-robust material.
Kumar团队生产的凝胶旋转碳纤维的测试为5.5至5.8 gigapascals（GPA），这是量度的终极拉伸强度的量度 - 并在354-375 GPA范围内具有拉伸模量。该材料是在佐治亚理工学院的连续碳化生产线上生产的，该材料是为这个DARPA项目构建的。
库马尔说：“对于任何报道的迄今为止的连续纤维来说，这是强度和模量最高的组合。”“在短尺寸的长度上，纤维抗拉力强度的测量高达12.1 GPA，这是锅基碳纤维有史以来最高的拉伸强度值。”
此外，库马尔（Kumar）指出，在纳米级测量的这些凝胶旋转碳纤维的内部结构显示出的缺陷少于最先进的商用碳纤维，例如IM7。具体而言，与溶液旋转产生的凝胶纤维相比，凝胶纤维纤维显示出低度的聚合物链纠缠。较少数量的纠缠导致以下事实：凝胶旋转使用的聚合物比溶液旋转方法较低。
Kumar and his team convert the gel-spun polymer mix into carbon fibers via a selective treatment process called pyrolysis, in which the spun polymer is gradually subjected to both heat and stretching. This technique eliminates large quantities of hydrogen, oxygen, and nitrogen from the polymer, leaving mostly strength-increasing carbon.
“It’s important to remember that the current performance of solution-spun PAN-based carbon fibers has been achieved after many years of material and process optimization – yet very limited material and process optimization studies have been carried out to date on the gel-spun PAN fiber,” Kumar said. “In the future, we believe that materials and process optimization, enhanced fiber circularity, and increased solution homogeneity will further increase the strength and modulus of the gel-spinning method.”
Filed Under:Materials • advanced
