大丝束碳纤维短切机理及断口形貌控制

Carbon fiber is a new kind of material with high performance, and its chopping technology plays an important role in its industry. To deal with the low production efficiency,rapid tool wear and theory deficiency of chopped carbon fiber, the chopping mechanism and shape control method of large tow carbon fiber are studied.In this project, the study object is large tow polyacrylonitrile ( PAN ) based carbon fiber. The chopping mechanism of carbon fiber under multiple field action(fluid field, stress field, temperature field) is discussed. The cutting model of carbon fiber is established. Besides, the section shape changes and stacking density changes during chopping procedure are analyzed. Then the cutting model of large tow carbon fiber is set up. Moreover,the genetic effect of short carbon fiber quality on composite properties is studied. The influences of structure defects and surface quality on the quality of chopping carbon fiber are investigated. The control method of fracture morphology basing on defects is studied. Furthmore, basing on the cutting mechanism and models, the chopping tool and its system are designed. The geometric model and life estimation method of chopping tool are investigated. The mechanical model and vibration model of chopping tool system are built up. The mapping relationship between tool system and chopped fiber is explored. Through the on-line monitoring of chopped carbon fiber quality, the active control and life prediction of tool system are done. Therefore, the chopped theory and technology of carbon fiber will be found after the implementation of this project, and the application of carbon fiber to civilian areas will be promoted.

碳纤维是公认的下一代高性能材料，短切是其重要的加工技术。针对目前碳纤维短切生产效率低、刀具磨损快、理论缺乏等现状，项目开展大丝束碳纤维短切机理及断口形貌控制研究。以大丝束聚丙烯腈（PAN）基碳纤维为研究对象，研究多场（流场、力场、温度场）综合作用下碳纤维的切断机理，建立碳纤维切断模型；分析丝束堆叠密度和截面形状在短切时的演变规律，建立碳纤维丝束切断模型；研究短切碳纤维质量对复合材料性能的遗传作用，探讨缺陷和表面质量对短切质量的作用规律，发现基于缺陷的断口形貌控制方法；基于切断机理与模型，完成短切刀具及系统的优化设计，建立短切刀具的几何模型与刀具寿命评价方法，建立短切刀具系统的力学模型和振动模型；探索刀具系统与短切纤维质量之间的映射关系；通过对短切碳纤维质量的在线监测，实现刀具系统的寿命预测与主动控制。项目的实施，将形成一套完善的碳纤维短切理论及技术，促进碳纤维产业向国民经济各个领域的应用。

碳纤维是公认的下一代新材料，短切是其重要应用形式，然而一直缺乏专门的制造技术与理论支撑。.项目开展了碳纤维单丝/丝束断裂机理、刀具磨损、装备设计、质量评价等研究。取得的主要理论成果如下：（1）揭示了碳纤维单丝切断机理，建立相关理论模型和数值模型，发现碳纤维的断裂在柔性支撑时主要受脆性折断作用，符合格里菲斯微裂纹理论，断口表面粗糙；在刚性支撑时，主要受赫兹接触的影响，断口形貌光滑；柔性支撑相比刚性支撑，极大的降低碳纤维切断力。（2）对比研究了不同预张力条件下有/无支撑约束对碳纤维单丝断裂行为的影响，发现预张力不利于支撑约束条件下的碳纤维断裂，但能促进无支撑条件下碳纤维的断裂。（3）揭示了丝束堆叠形状在短切刀具与浆料作用下的碳纤维形变规律，揭示了大丝束碳纤维切断机理，发现丝束的断裂是由刀具接触内侧向外侧扩展的。（4）观察了短切刀具的磨损过程，发现磨粒磨损是刀具磨损的主要原因，月牙湾磨损是主要形式；提出了磨损量差值和磨损类比两个评价短切刀具寿命的方法。（5）以短切碳纤维长度、宽度均匀性标准差、断口整齐度和断面形貌作为质量评价指标，应用熵权模糊综合评价方法，构建了短切碳纤维的质量评价方法。（6）结合碳纤维断裂机理、断裂行为和质量评价方法，优化设计了基于弹性支撑的径向切割式短切碳纤维设备，以上浆工艺为对象，探索了优化生产工艺，搭建了速率>50 m/min、年产达200吨的短切碳纤维中试生产线；（7）揭示了复合材料性能与短切碳纤维结构参数之间的映射规律，针对电磁屏蔽领域，完成了电磁屏蔽效能>30 dB、厚度<0.2 mm的高性能超薄碳纤维复合材料的设计与制造，符合电磁屏蔽商用标准。.项目在International Journal of Machine Tools and Manufacture、Textile Research Journal等国内外权威期刊上发表学术论文19篇，其中SCI收录17篇，EI收录2篇，培养研究生9人，向行业企业技术转让成果2项，转让费22万元。项目的实施，丰富了碳纤维短切技术理论体系，有效的促进了碳纤维产业的发展。