Collaborative Research: Microwave Heating of Carbon Nanotube Coatings to Enable Rapid Welding in 3D-Printed Polymer Structures

塑料部件增材制造中最关键的问题之一是由于沉积的聚合物层之间的界面焊接薄弱而导致的零件强度差。制造部件的均匀加热不能解决这个问题，因为它会导致3D打印结构翘曲，从而影响三维（3D）打印作为一种塑料制造技术的机械可靠性。本研究探讨了一种新的制造工艺，在3D打印中使用的塑料细丝上沉积一层薄薄的碳纳米管（CNTs）。微波照射打印部件会使碳纳米管受热，从而使焊接处的局部聚合物熔化，从而显著提高部件的机械强度。如果成功，该项目所实现的增材制造技术有可能克服传统制造的聚合物部件（如注射成型、挤出成型和机械加工）与增材制造技术打印的部件之间的差距。具体来说，这项工作使用实验和计算相结合的方法来测量和模拟碳纳米管负载的聚合物薄膜的响应，以便直接捕获涂层的热动力学。这将通过结合交流电介电测量、红外成像和有限元建模（结合射频加热和薄涂层中的传热）来完成。随后将对涂层、材料挤压和受控微波暴露过程进行大规模调查，以展示这一概念如何转化为增材制造环境，重点是强度改进（在垂直打印拉伸棒上测量）和可靠性。微波照射将使用同步红外成像和实时调整正向功率来产生一致的指定加热处理。这项工作的知识意义源于将微尺度碳纳米管加热转化为复杂的宏观3D打印结构中焊缝的加工-结构-性能关系。这项工作将对聚合物物理、纳米材料渗透、微波物理、塑料加工、先进制造等多个科学和工程领域产生重大影响。

One of the most critical problems in additive manufacturing of plastic components is poor part strength caused by weak interfacial welding between the deposited polymer layers. Uniform heating of the manufactured part cannot solve this problem because it can cause warping of the 3D-printed structure that affects the mechanical reliability of three-dimensional (3D) printing as a plastic manufacturing technique. This research examines a novel manufacturing process where a thin coating of carbon nanotubes (CNTs) is deposited on the plastic filaments used in 3D printing. Microwave exposure of the printed parts causes the CNTs to heat that allows for localized polymer melting at the welds, resulting in markedly improved mechanical strength of the part. If successful, the additive manufacturing technology enabled by this project has the potential to overcome the current disparity between traditionally manufactured polymer parts such as injection molding, extrusion molding and machining as compared to parts printed with additive manufacturing techniques. Specifically, this work uses a combination of experimentation and computation to measure and model the response of CNT-loaded polymer films in order to directly capture the coating thermal dynamics. This will be done using a combination of alternating current dielectric measurements, infrared imaging, and finite-element modeling (combining radio frequency heating and heat transfer in thin coatings). This will be followed by a scaled-up investigation of the coating, material extrusion, and controlled microwave exposure processes to demonstrate how this concept translates to an additive manufacturing context, with an emphasis on strength improvements (as measured on vertically printed tensile bars) and reliability. The microwave exposure will be carried out using simultaneous infrared imaging and real-time adjustment of forward power to yield consistent, specified heating treatments. The intellectual significance of the work stems from the translation of microscale CNT heating to processing-structure-property relationships for welds in complex, macroscale 3D printed structures. This work will have a strong impact on multiple scientific and engineering fields including polymer physics, nanomaterial percolation, microwave physics, plastics processing, advanced manufacturing.