碳纳米管涂层纤维的原位树脂成型监测及传感机理研究

The next-generation of hierarchical composites needs to have built-in functionality to continually monitor and diagnose their own health states. This proposal includes a novel strategy for in-situ monitoring the processing stages of composites by co-braiding CNT-enabled fiber sensors into the reinforcing fiber fabrics. This would present a tremendous improvement over the present methods that excessively focus on detecting mechanical deformations and cracks. The CNT enabled smart fabrics, fabricated by a cost-effective and scalable method, could be highly sensitive to monitor and quantify various events of composite processing including resin infusion, onset of crosslinking, gel time, degree and rate of curing. By varying curing temperature, vacuum pressure and resin formulation, the results and trends derived from the systematic study will be further compared by rheological and DSC tests. More importantly, upon wisely configuring the smart fabrics with a scalable sensor network, localized processing information of composites could be achieved in real time. In addition, the smart fabrics that are readily and non-invasively integrated into composites could provide life-long structural health monitoring of the composites, including detection of deformations and cracks. Considering the non-invasiveness, robustness, and large-area deployment capabilities as well as its built-in dual functionalities for structural health monitoring of composites over its lifespan, we expect the high advantage of smart fabrics for enhancing safety, performance and reliability of future lightweight composites.

树脂基复合材料成型阶段极易产生孔隙、贫/富胶、夹杂、固化不完全等工艺缺陷，极大地影响加工质量与成本。相比传统检测手段，基于碳纳米管（CNT）的传感技术在轻质、柔性随形和原位监测等方面具有很大优势。然而，由于CNT有效表征手段及加工-结构-性能关系系统研究的缺失，现阶段CNT技术对复材树脂成型过程的传感机理研究仍处于空白状态。本项目从构筑可与复材织布共编织、共固化的CNT涂层纤维传感器开始，控制CNT在复材纤维束表面沉积的微观结构与形貌，建立传感单元加工工艺参数-组织结构形貌-阻变灵敏性能的关系，探索CNT传感器在不同树脂交联反应条件下的传感规律，揭示传感器对树脂浸润速度、流动状态、凝胶时间、固化程度与固化速率等重要物理参量的传感机理，最后以矩阵式传感网络的形式验证多点局部状态分布的监测应用。本项目的开展将为研制新一代可监测自身全生命周期健康状态的复合材料提供理论基础和技术支撑。

随着纤维增强树脂基复合材料制造工艺的日臻成熟以及在飞机、船舶、汽车、土木工程等装备、设施、建筑的大规模应用，其引发的质量保障与使用安全问题备受关注。高性能复合材料的自主健康监测诊断成为国际航空航天领域的前沿攻关方向。结合先进的碳纳米技术，本项目构建了一种可嵌入树脂基复合材料结构、匹配成型工艺、原位监测加工成型阶段的纤维传感策略。研究致力于探索并验证碳纳米涂层纤维传感器对树脂固化反应过程中关键物理参量（如树脂扩散速率、流动状态、凝胶时间、固化速率与程度）的在线监测能力，通过分析潜在的加工-结构-性能关系，揭示碳纳米传感网络微观结构对复材加工监测信号响应的影响规律，从而获悉传感机理。项目完成了1）碳纳米纤维传感器的加工制备及与树脂基复合材料一体化工艺的优化设计：结合高效的连续加工及一体化成型工艺，通过在制造阶段将碳纳米涂层纤维传感器无损地编织集成至复材结构内部，实现对树脂固化过程的健康监测技术构建。2）传感器微观结构对电学传感行为的性能影响分析及控制：建立了复材树脂模塑成型全过程的实时监测方法，深入分析纤维传感器的过程监测性能。利用多种表征手段明确了碳纳米结构对传感器信号的影响规律。显著的三段式压阻行为（疾速上升-剧烈衰减-逐渐平稳）与固化反应进程的三个典型阶段（凝胶、硬化、后固化）密切关联，有助于清晰定位识别体系所处成型时期与实时反应状态。采用碳纳米管涂层的纤维传感器占据了绝对性能优势，Gain Factor可达1600%。3）传感器在树脂不同加工环境下的传感规律及状态监测机理：测试了传感器在复材不同加工条件（固化温度、固化剂配比、干点/气泡情况）下的监测效应，揭示了复材成型过程的结构依赖性监测机理，并探索利用传感阵列监测复材多点局部位置的加工状态分布。本项目成果可为用于航空航天复合材料整体部件的在线加工监测技术提供指导和支撑，为设计高性能、长寿命、多模式健康监测的智能复合材料提供更为充分的依据。