EPD共沉积CNTs与SiCnws协同改性C/C复合材料的制备与强韧机制

In order to tackle the problem of matrix annular cracks and fiber/matrix interface relaxation of C/C composites components with sharp corners and thin walls, thus, fully improve the integral properties of C/C composites, the multi-dimensional reinforcing structure based on carbon fibers with co-deposited of CNTs and SiCnws is proposed. The project plans to achieve the co-deposition of CNTs+SiCnws using EPD. The ‘macro-micro-nano’ compositive reinforcing system improves the properties of the C/C composite by introducing adjusted carbon fiber/matrix within pyrocarbon interface, such modified interface will optimize the structure by deflecting cracks. The project will study the controllable process of co-deposition of CNTs+SiCnws; the influence of the densification mechanism and microstructure of C/C composite after the introduction of CNTs+SiCnws; the design and optimization of interface; explore the influence of CNTs+SiCnws and interface to the macro-mechanical and micro-mechanical properties, stress distribution, the pattern of the interface binding and internal friction of the C/C composite; reveal the synergistic toughening mechanism of the carbon fiber-CNTs-SiCnws coupling inferface.The project will lay the foundation of advanced fabrication of C/C composite, develop and enrich the fabrication method, structural design and toughening mechanism.

针对碳/碳（C/C）复合材料尖角锐形、薄壁构件服役过程崩块、界面松弛开裂等频发现象衍生的性能制约难题，提出在碳纤维表面共沉积碳纳米管（CNTs）、碳化硅纳米线（SiCnws）构建多尺度增强体系，协同界面设计，全面提升C/C复合材料性能的新思路。本项目拟借助EPD（电泳沉积）方法实现CNTs+SiCnws的共沉积，“宏-微-纳”多尺度改善基体性能，拟利用热解碳界面层引入调控碳纤维/基体界面结合状态，通过优化界面层致裂纹偏转改善材料假塑性。系统研究EPD加载CNTs+SiCnws的可控掺杂工艺，界面层的设计与优化，探究CNTs+SiCnws与界面层引入对C/C复合材料致密化过程、基体微观组织结构和力学性能的影响规律，揭示碳纤维、CNTs、SiCnws的协同强韧机制。本项目研究结果将为先进C/C复合材料构件制备奠定基础，同时丰富和发展复合材料的制备方法、结构设计与强韧化理论。

本项目通过在碳纤维（CF）表面共沉积碳纳米管（CNTs）、碳化硅纳米线（SiCnws）实现“宏-微-纳”多尺度增强体系构建，旨在解决尖角锐形、薄壁C/C复合材料构件在服役过程中出现的崩块、界面松弛开裂等现象衍生的性能制约问题。借助电泳沉积（EPD）方法，通过对EPD过程中CNTs+SiCnws共混电泳液的浓度、成分配比、沉积电压和沉积形态等参数优化，获得了微纳米孔隙结构可调的CF/CNTs+SiCnws多尺度增强结构。通过致密化C/C复合材料工艺优化，提高了CH4气体分子在引入CNTs+SiCnws共沉积体系预制体内部扩散的均匀性，改善了热解碳（PyC）基体整体均匀度和致密化度，实现了CNTs+SiCnws增强C/C复合材料的快速致密化。在此基础上，通过CVI和化学接枝的方法，在CF表面引入不同织构、不同厚度PyC界面层和不同尺度氧化石墨烯（GO）界面层，进一步优化了CF/CNTs+SiCnws多尺度增强结构与PyC基体在微纳尺度上的界面结合。研究发现，CNTs+SiCnws多尺度增强结合界面改性，可有效提高C/C复合材料的失效应力和断裂韧性，避免了CNTs团聚造成的PyC结晶度下降从而造成界面层韧化效果失效的缺陷，同时在优化界面结合的前提下CNTs+SiCnws的混杂多层级分布使得对PyC基体的强化和韧化效果实现了协同，进而更好的实现了PyC基体强化和韧化的协同。