CAREER: Material-Process-Property Relationships of Additive Manufacturing with Polymer Nanocomposites

这项学院早期职业发展(Career)计划拨款将支持聚合物纳米复合材料或PNS的研究，PNS由聚合物基质中的纳米颗粒组成。这些体系以可调的方式结合了聚合物的良好性能，例如重量轻、机械韧性和柔韧性，以及填料的高强度、导电性和导热性。这样的组合产生了传统材料无法实现的独特的综合性能。这些材料被用于许多新兴技术，如能量储存、生化传感、柔性电子和人造组织工程，这些技术对国家的繁荣和竞争力至关重要。实现PNS的主要挑战包括开发新的制造方法，以高分辨率处理这些材料，并精确控制最终产品中决定最终部件性能的填料形态。新出现的添加剂制造方法，特别是直接墨水写入(DIW)，通过喷嘴分配并以高空间控制沉积PN“墨水”，已被证明实现了具有可控填充形态的PN部件的高分辨率制造。该奖项支持基础研究，这些研究将提供所需的知识，以增加制造具有高可定制化、精确度和精确度的“按设计”属性的PN部件。这一能力将使许多对社会健康、国家安全和能源行业至关重要的新兴技术成为可能，例如可定制的生化传感器、高性能储能设备和轻型高强度军事装备制造。这项教育工作将为将加法制造融入机械工程课程提供一个模式，这反过来将为下一代制造业劳动力配备急需的技能集。该项目将开展的外联活动将提高公众对添加剂制造和灵活电子概念的认识和准备。尽管添加剂制造在PNS加工中具有很好的潜力，但在原材料特性-工艺参数-最终部件特性之间的关系方面存在知识差距。本研究将通过一个实验和计算建模框架来解决这一知识差距，该框架将揭示影响最终零件性能的沉积机制。为此，将通过一种新的粘弹性材料模型来模拟PN油墨，该模型结合了填料形态在时间和空间上变化对主体油墨流变性的影响。该模型将用于实验验证的计算流体力学模拟，该模拟将输出印刷过程中沉积细丝中的关键应力和应变参数。最后，将进行研究，以了解这些模型输出如何转化为纳米颗粒的特定形态以及制造部件的电气和机械属性。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 Faculty Early Career Development (CAREER) Program grant will support research into polymer nanocomposites or PNs, consisting of nanoparticles within a polymer matrix. These systems combine favorable properties of the polymers, e.g. light weight, mechanical toughness and flexibility, and the fillers with their high strength, electrical and thermal conductivity, in a tunable fashion. Such combinations lead to unique overall properties that cannot be achieved by conventional materials. These materials are utilized in many emerging technologies such as energy storage, biochemical sensing, flexible electronics and artificial tissue engineering important to the national prosperity and competitiveness. A primary challenge in realizing PNs involves the development of new manufacturing methods to process these materials with high resolution and precise control over filler morphology within the final product that dictates the final part properties. Emerging additive manufacturing methods, particularly direct-ink-writing (DIW), where the PN "inks" are dispensed through nozzles and deposited with high spatial control, has been shown to achieve high resolution manufacturing of PN parts with controllable filler morphologies. This award supports the fundamental research that will provide the knowledge needed for additively manufacturing PN parts having "as-designed" properties with high customizability, precision and accuracy. This capability will enable many emerging technologies critical to societal health, national security and the energy sector such as customizable biochemical sensors, high performance energy storage devices and lightweight high-strength military equipment manufacturing. The educational effort will provide a model for integration of additive manufacturing into the mechanical engineering curriculum which in turn will equip the next generation manufacturing workforce with a much needed skill-set. The outreach activities that will be realized in this project will increase the public awareness and readiness for the additive manufacturing and flexible electronics concepts.Despite the promising potential of additive manufacturing in processing of PNs, there exists a knowledge gap in regard to relationships between raw material properties-process parameters-final part properties. This research will address this knowledge gap through an experimental and computational modeling framework that will reveal the deposition mechanisms influencing the final part properties. To this end, PN inks will be modeled through a new viscoelastic material model that incorporates the effect of temporally and spatially varying filler morphology on the bulk ink rheology. This model will be used in experimentally validated computational fluid dynamics simulations that will output critical stress and strain parameters in the deposited filaments during the printing process. Finally, studies will be conducted to understand how these model outputs translate to specific morphologies of nanoparticles as well as the electrical and mechanical properties of the manufactured parts.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.