激光烧结多尺度纤维增强型复合材料的关键工艺机理研究

Development of multi-scale fiber-reinforced polymeric composite powders are a novel and effective approach to facilitate the selective laser sintering (SLS) process as well as significantly enhance the mechanical properties of printed materials. The interfacial defects of fiber/polymer, the disalignment and agglomeration of fibers and the limited fiber loading are the critical issues resulting in inferior mechanical performance of laser-sintered composites. In this work, the systematic development of fiber-reinforced composites is proposed including powder development, powder evaluation and optimization of SLS. The microfibers could be encapsulated by polymer resins to form the semi-spherical powders through an emulsion process and then nanofibers are added to the suspension so as to absorb onto the surface to the solidify powders in the liquid system. The powder properties are controllable to adapt into the SLS process in order to print multi-scale fiber-reinforced polymeric composites. The theoretical modeling and experimental study are implemented to investigate the influence of process parameters on mechanical properties as well as optimize parameter sets. Moreover, the systematic investigation is conducted to reveal the relationship of material-process-structure-property. The interface defects of fibers and polymers could be avoidable and the cross-scaled fibers could enhance the mechanical strength, toughness and modulus simultaneously.

激光烧结跨尺度纤维增强型复合材料是提升树脂基增材制造材料综合力学性能和功能性的有效途径。为解决目前烧结成型复材微观结构呈现纤维分布不均，纤维与树脂界面弱粘合，纤维添加量受限等严重问题，本项目围绕“粉末制备-粉末评估-激光烧结”的核心体系，提出采用乳化溶液沉积法制备多尺度纤维增强型粉末的创新工艺，深入探究异相成核机理促进的树脂包覆微米级纤维的制粉机制和纳米纤维吸附的覆膜机理；建立系统粉末评估体系，探明粉末形貌，粉末流动和微观结构的主要影响因素，以满足激光烧结工艺对粉末基体的严苛要求；通过激光模型理论预测和烧结实验测试表征，优化工艺参数和材料配比，解决纤维与树脂异质界面的粘合问题并优化多尺度纤维的空间排布，深入研究多尺度纤维协同增强打印材料综合机械性能的科学问题，从而建立激光烧结工艺“材料-工艺-结构-性能”的完整体系，实现激光烧结复合材料/结构功能一体化设计制造的目标。

激光烧结跨尺度纤维增强型复合材料是提升树脂基增材制造材料综合力学性能和功能性的有效途径。为解决目前烧结成形复材微观结构呈现纤维分布不均，纤维与树脂界面弱粘合，纤维添加量受限等严重问题，本项目围绕“粉末制备-粉末评估-激光烧结”的核心体系，提出热驱动固液分离异质形核法，并完成纳米碳管覆膜,制备核-壳结构纤维-树脂复合粉末,深入探究异相成核机理促进的树脂包覆微米级纤维的制粉机制和纳米纤维吸附的覆膜机理；建立系统粉末评估体系，探明粉末形貌，粉末流动和微观结构的主要影响因素，以满足激光烧结工艺对粉末基体的严苛要求；揭示热场耦合结晶相变对粉末床烧结成形的影响，建立激光选区烧结模型有效预测熔融区域及确定工艺窗口；解决纤维与树脂异质界面的粘合问题并优化多尺度纤维的空间排布，深入研究多尺度纤维协同增强打印材料综合机械性能的科学问题，既有利于提升成形复材构件的综合力学性能，且提升其导电及导热性能。建立跨尺度热力耦合模型，优化工艺扫描路径策略以实现宏观结构的保形控性。通过数据驱动/神经网络模型建立材料特征、工艺参数等多元因数对成形构件性能的影响关系，引入宏观结构拓扑设计以实现材料-工艺与结构的协同优化。从而建立激光烧结工艺“材料-工艺-结构-性能”的完整体系，实现激光烧结复合材料/结构功能一体化设计制造的目标。