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

该奖项支持一个针对热固性聚合物的新型3D打印方法--局部正面固化辅助3D打印的合作研究项目。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。目前可用于制造热固性聚合物部件的方法包括传统模塑和新开发的无模3D打印。这些方法包括两个步骤：沉积处理和后处理固化，这两个步骤都是耗能和耗时的。在局部化正面固化辅助3D打印中，沉积和固化在一步过程中同时完成。使用外部热源来初始化固化过程，并且放热固化反应产生的热量使固化能够在沉积时通过材料自我传播。这种新方法有可能对使用热固性聚合物的产品的设计、组装和制造产生影响。因此，它可能会导致许多涉及国家利益的行业发生重大变化并提高竞争力，例如汽车、航空航天和海洋行业。这个项目将吸引研究生和本科生参与研究活动，从而为他们进入先进的制造业劳动力做好准备。基于这项研究的外展活动将被用于高中夏令营和在线视频，以教育学生和普通公众关于先进制造业的知识。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、热固性树脂的粘弹性行为和印刷结构几何保真度之间的关系；(3)检验正面速度特定范围将导致较高层间结合强度的假设；以及(4)揭示局部正面速度对印刷结构机械性能的影响。为了实现这些目标，研究小组将采用理论和实验两种方法。具体地说，在反应动力学的基础上，对固化剂结构和浓度对前沿固化速度和前沿传播距离的影响进行建模和模拟，并用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。正面速度对印刷结构层间结合强度和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智力优势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.