Collaborative Research: Localized Frontal Curing-Assisted 3D Printing of Thermosetting Polymers

该奖项支持一项关于热固性聚合物的新型3D打印方法的合作研究项目，即局部正面固化辅助3D打印。热固性聚合物广泛应用于飞机、航天飞机、汽车、船舶、桥梁、家具等领域。目前可用于制造热固性聚合物部件的方法包括常规成型和新开发的无模具3D打印。这些方法涉及两个步骤：沉积处理和后处理固化，这两个步骤都是能源密集型和耗时的。在局部正面固化辅助3D打印中，沉积和固化在一步过程中同时完成。外部热源用于初始化固化过程，并且由放热固化反应产生的热量使得固化能够在材料沉积时自传播通过材料。这种新方法有可能影响产品设计、组装和使用热固性聚合物的产品制造。因此，它可能会导致重大变化，并提高许多国家利益行业的竞争力，如汽车，航空航天和海洋工业。该项目将使研究生和本科生参与研究活动，从而为先进的制造业劳动力做好准备。基于研究的推广活动将用于高中夏令营和在线视频，以教育学生和公众了解先进制造业。 研究目标有四个：（1）确定固化剂浓度和印刷切片尺寸对正面速度和正面传播距离的影响;（2）了解局部正面速度、热固性树脂的粘弹行为和印刷结构的几何保真度之间的关系;（3）检验特定范围的正面速度将导致更高的层间结合强度的假设;（4）揭示局部前沿速度对印刷结构力学性能的影响。为了实现这些目标，研究小组将采用理论和实验方法。具体而言，固化剂结构和浓度对正面固化速度和正面传播距离的影响将基于反应动力学建模和模拟，然后通过高分辨率红外相机进行验证。热固性树脂的粘弹性行为将通过实时流变学表征和数据拟合来研究。正面速度对层间结合强度和打印结构的机械性能的影响将通过实验测试和统计分析来揭示。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This award supports a collaborative research project on a novel 3D printing method for thermosetting polymers, localized frontal curing-assisted 3D printing. Thermosetting polymers are widely used in aircraft, space shuttles, cars, boats, bridges, furniture, and so on. Currently available methods to manufacture thermosetting polymer parts include conventional molding and newly-developed mold-free 3D printing. These methods involve two steps: deposition processing and post-processing curing that are both energy-intensive and time-consuming. In localized frontal curing-assisted 3D printing, deposition and curing are completed simultaneously in a one-step process. An external heat source is used to initialize the curing process and the heat produced by the exothermic curing reaction enables curing to self-propagate through the material as it is deposited. The new method has the potential to impact product design, assembly, and the manufacture of products using thermosetting polymers. As a result it could potentially lead to significant changes and increased competitiveness in many industries of national interest, such as the automotive, aerospace, and marine industries. This project will engage graduate and undergraduate students in the research activities thus preparing them for the advanced manufacturing workforce. Outreach activities based on the research will be used at high school summer camps and for online videos to educate students and the general public about advanced manufacturing. There are four research objectives: (1) to determine effects of curing agent concentration and printing slice size on frontal velocity and front propagation distance; (2) to understand relationships between localized frontal velocity, viscoelastic behavior of thermosetting resins, and geometric fidelity of printed structures; (3) to test the hypothesis that a specific range of frontal velocity will result in higher interlayer bonding strength; and (4) to reveal effects of localized frontal velocity on the mechanical performance of printed structures. To achieve these objectives, the research team will employ both theoretical and experimental approaches. Specifically, effects of curing agent structures and concentration on frontal curing velocity and front propagation distance will be modelled and simulated based on the reaction kinetics and then verified by high-resolution infrared camera. Viscoelastic behavior of thermosetting resins will be studied via real-time rheology characterization and data fitting. Effects of frontal velocity on interlayer bonding strength and mechanical performance of printed structures will be revealed by experimental tests and statistical analysis.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.