环氧化石墨烯/碳纤维增强树脂基复合材料的界面构筑及增强、增韧机理研究

Carbon fiber (CF) surface treatments can significantly improve interfacial adhesion strength while usually reduce the toughness of composites. In this study, we propose a novel method to graft epoxy functionalized graphene oxide (EP-GO) onto polyphosphazene functionalized carbon fibers through chemical reaction to form the EP-GOs grafted CF hierachial reinforcement. Herein, the controllable polymerization of polyphosphazene can introduce a stable and uniform distribution of numerous amino groups onto CF, which provide carbon fiber with "high reactivity" and will easily react with sufficient epoxy groups on EP-GOs. And then the EP-GOs grafted CFs can react with curing agent to interlink matrix through a great quantity of chemical bonding. In addition, the higher aspect ratio and the planar geometry of EP-GOs in the interface of composites will enhance the mechanical interlocking and give rise to crack deflection. The aim of the study is to achieve the optimal interfacial strength and toughness of carbon fiber reinforced composites due to the appropriate stress transfer and the enhanced energy absorption by changing the interface interaction between fiber and matrix and the morphologies of EP-GOs in the interface. The research work mainly focuses on: (1) to regulate and control the grafting density, distribution and surface morphologies of EP-GOs on carbon fibers; (2) to investigate the relationship between the interfacial properties and surface structure of CF after grafting EP-GOs; (3) to investigate and exposit the interfacial strengthening and toughening mechanisms of EP-GOs grafted CF reinforced composites. On the basis of above studies, it will exploit a new carbon fiber surface treatment method and develop interfacial theory to guide the design and preparation of high performance carbon fiber reinforced composites.

针对现有碳纤维表界面改性中存在的提高复合材料界面强度却牺牲其界面韧性的问题，本项目提出采用化学方法将大比表面积的二维结构环氧化石墨烯接枝到"活性"碳纤维表面，即先在碳纤维表面预接枝稳定、可控，且富含氨基的聚膦腈，环氧化石墨烯再与聚膦腈表面氨基反应而接枝于碳纤维表面，构筑具有三维结构的环氧化石墨烯接枝的碳纤维多尺度增强体。通过环氧化石墨烯调控碳纤维复合材料的界面相互作用和界面微观结构，以引入新的能量耗散机制，实现全面提高复合材料的界面强度和韧性。主要研究内容：(1) 影响碳纤维表面环氧化石墨烯接枝密度、分布，形貌结构的规律；(2)环氧化石墨烯接枝碳纤维的表面结构和性质与复合材料界面性能之间的构效关系；(3)探明新界面相调控复合材料界面性能的作用机制，揭示界面增强、增韧机理。本项目的研究，将推动纤维表面改性技术和复合材料界面理论的发展，指导设计和制备高性能碳纤维增强树脂基复合材料。

碳纤维复合材料因轻质高强的特性获得广泛应用，但纤维与基体间的界面结合较弱，不能有效传递载荷而影响碳纤维高性能的充分发挥。针对这一问题，我们提出采用化学方法将环氧化石墨烯接枝到碳纤维表面构建三维结构多尺度增强体，即在本项目中预先在碳纤维表面原位接枝富含氨基的聚膦腈，增加纤维表面高反应活性的基团数量，再接枝环氧化石墨烯，通过界面物理和化学作用的协同效应更大程度地改善复合材料界面性能。我们通过研究发现，碳纤维表面原位接枝聚膦腈后，表面引入了大量高反应活性的氨基，通过反应时间、单体浓度等可以调控接枝聚膦腈膜的量，界面剪切强度提高幅度可达73.2%，单丝本体拉伸强度也提高了10.6%，且改性碳纤维和复合材料耐热氧性均能得到改善，阐述了氨基化碳纤维复合材料界面增强机制。三维结构环氧化石墨烯接枝碳纤维多尺度增强体进一步有效地改善了复合材料的界面性能，使界面剪切强度提高了106.5%。接枝的环氧化石墨烯在纤维和树脂基体间不仅起化学键接和机械啮合作用，其均匀分布可抑制界面层裂纹扩展，改变裂纹扩展路径增加能量耗散，改善复合材料界面层韧性。本项目的研究成果为碳纤维表面改性提供了新的思路和方法，同时这类拥有优异性能的多尺度碳纤维复合材料将在航空航天和汽车工业领域具有潜在的应用。