3D打印连续纤维增强热塑性复合材料结构冲击损伤的机理及定量监测研究

Three-dimensional (3D) printing technology does not require a mold, has high flexibility and saves materials, which will be applied widely in the field of continuous fiber-reinforced composite structures manufacturing. However, currently 3D printed continuous fiber-reinforced composite structures cannot be applied due to the following challenges: (1) The characteristics of internal multi-interface and single tow in single-layer make it more sensitive to impact loads; (2) The characteristics of microscopic multiphase heterogeneity and macroscopic anisotropy make it complex and difficult to study the impact damage, so the mechanism of impact damage is unknown; (3) Damage monitoring costs are high and accuracy is low due to the transient and non-linearity of the impact response. Therefore, the project takes 3D printed continuous fiber-reinforced thermoplastic matrix composite structures with excellent recyclability and moldability as the research object. Firstly, the multi-scale model considering microscopic features, multiple interfaces, residual thermal stress, matrix viscoelasticity and strain rate effect is established. Combined simulations and experiments, the mechanism of impact damage initiation and propagation is revealed. Then, a three-phase force-electric coupling model of 3D printed composite substrate-interface-conductive coating is established. Combined simulations and experiments, the quantitative relationship between the impact damage pattern, shape and degree of composite structures and the resistance change of conductive coating is investigated. Finally, based on the impact damage mechanism and the conductive coating-damage quantitative relationship, the monitoring research of impact damage of 3D printed composite plate and shell structures with the patterned conductive coatings is carried out. This research could provide theoretical guidance for impact performance improvement and engineering application of 3D printed composite structures.

3D打印不需模具，生产柔性高，节约材料，在连续纤维复合材料结构制造中应用前景广阔。但是，目前3D打印连续纤维复合材料应用还存在以下瓶颈：内部多界面和单层单丝束特性使其对冲击载荷更加敏感；微观多相非均质和宏观各向异性使其冲击损伤研究复杂困难，损伤机理未明；冲击响应瞬时和非线性强，损伤监测成本高、准确度低。本项目以回收性和成型性好的热塑性基体3D打印连续纤维复合材料结构为研究对象，首先建立考虑微观特征、多界面、残余热应力、基体粘弹性、应变率效应等的多尺度模型，结合实验揭示冲击损伤初始和演化机理；然后，建立含导电涂层的复合材料基底-界面-涂层三相力-电耦合模型，结合实验研究损伤模式、形状和程度与涂层电阻变化之间的定量关系；最后，结合冲击损伤机理和导电涂层-损伤定量关系，开展基于图案化导电涂层的3D打印复材板壳结构冲击损伤监测研究。研究成果可为3D打印复材结构抗冲击性能改进和工程应用提供理论基础。

3D打印基于逐层堆积的增材制造思想，具有节约材料、不需模具、复杂几何成型能力强、制造柔性高等优点，可能为制造业带来颠覆性的变革。纤维增强聚合物基复合材料密度低，比模量和比强度高，是汽车、飞机、高铁等载运装备轻量化的重要材料。将3D打印与复合材料结合，交叉融合，会产生明显的协同效应，科学研究和工程应用价值巨大，但冲击损伤是其服役过程中的重要考验。因此，本项目对3D打印连续纤维增强聚合物基复合材料进行了系统研究，建立了3D打印连续纤维复合材料试样制备和静动态力学性能测试方法，通过多种静动态力学实验和仿真研究，多尺度揭示了3D打印连续纤维复合材料的冲击损伤机理；开发了可用于3D打印复合材料的导电涂料，建立了含导电涂层的3D打印复合材料结构力-电耦合仿真模型，研究了导电涂层的电阻变化率、灵敏度系数与复合材料结构的受载和应变之间的关系；设计了多种导电涂层图案，提出并验证了基于导电涂层的复合材料结构冲击损伤监测方法，研究成果可以为3D打印复合材料的抗冲击性能改进、结构设计分析和损伤监测提供一定的理论基础和有益参考，对3D打印复合材料的发展和工程应用具有重要意义。