Two-component Robotic Extrusion Additive Manufacturing of Concrete Structures: Silicone-solution Phases and Fiber Distributions for Functionally Graded Materials

使用混凝土材料的增材制造有可能彻底改变建筑基础设施建设的未来。然而，目前的增材制造技术在生产结构更坚固的混凝土方面受到限制，主要是因为在工艺中使用单一材料以及混凝土混合物挤出中复杂的工艺物理学。该奖项支持基础研究，以推进双组分机器人增材制造（混凝土和可调化学液相），提供创新方法来创建混凝土组件的尖端设计和制造。该项目将基于挤出工艺的科学与材料和化学研究结合在一起，实现了混凝土材料的特性，这些特性可以在制造层之间进行设计和调整，即产生功能梯度。研究的双组分挤出增材制造可用于开发高度工程化的基础设施组件，并将有利于建筑增材制造行业更好地利用不断增长的全球市场。该研究将支持美国工业在快速增长的混凝土增材制造技术领域保持竞争力，因为它将继续在建筑和住房领域推广。该项目还将通过教育和外联活动，包括高中的研讨会和研究机会，刺激制造业创新，扩大多样性，本研究旨在对分层机器人增材制造中的双组分挤出工艺以及含有机硅的纤维增强混凝土的物理和化学特性有一个基本的了解，含有亲水性或疏水性化合物以开发可调功能梯度混凝土。双组分挤出的主要科学障碍在于需要关于两种材料混合的物理学的基础知识。这项研究的动机是了解如何利用双组分工艺以及分层界面处含硅混凝土化合物的化学性质来调节材料的局部梯度特性并提高其承载能力。该项目将阐明（i）材料流变特性与加工参数之间的基本物理关系（流速、压力、挤出喷嘴中的在线混合）结合实验方法和分析模型，（ii）通过亲水和疏水化学的界面结合机制的新工程，和（iii）新的制造更强和更强硬的功能梯度混凝土材料，通过将纤维增强材料的各种配置研究的实验分析建模方法，包括断裂力学。通过该项目获得的增强的材料加工知识将有助于利用更强的工程材料的有效设计和制造的机会。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。

Additive manufacturing using concrete materials has a potential to revolutionize the future of building infrastructure constructions. Current additive manufacturing techniques, however, are limited in their ability to produce more structurally robust concrete, mainly because of employing a single material in the process and complex process physics in concrete-mixture extrusion. This award supports fundamental research to advance two-component robotic additive manufacturing (with concrete and adjustable chemical liquid phase) that provides an innovative method to create cutting-edge designs and manufacturing of concrete components. The project brings together work on the science of an extrusion-based process with materials and chemistry research, achieving concrete materials with properties that can be engineered and tuned across fabricated layers, namely, to produce functional gradient. The two-component extrusion additive manufacturing investigated can be applied to develop highly engineered infrastructure components and will benefit the construction additive manufacturing industry to better exploit the growing global market. The study will support the U.S. industry in maintaining its competitiveness in a rapidly growing technological field of concrete additive manufacturing, as it continues to spread in the construction and housing sectors. The project will also stimulate manufacturing innovations and broaden diversity through educational and outreach activities including workshop and research opportunities to high-school, undergraduate and graduate students from underrepresented groups.This research aims at a foundational understanding of the two-component extrusion process in layer-wise robotic additive manufacturing and the physical and chemical characteristics of fiber-reinforced concrete with silicone-containing hydrophilic or hydrophobic compounds to develop tunable functionally graded concrete. The primary scientific barriers in two-component extrusion reside in the need for fundamental knowledge about the physics of intermixing with two materials. This research is motivated to understand how the two-component process, together with the chemistry of the silicone-containing concrete compounds at the layered interfaces, be leveraged to tune the local gradient properties of materials and improve their load-bearing capacities. The project will elucidate (i) the underlying physical relationship between the materials' rheological properties and the processing parameters (flow rates, pressures, in-line intermixing in an extrusion nozzle) combining an experimental method and analytical model, (ii) the novel engineering of the interfacial bonding mechanisms through hydrophilic and hydrophobic chemistry, and (iii) new manufacturing of stronger and tougher functionally graded concrete materials by incorporating fiber reinforcements of various configurations investigated by an experimental-analytical-modeling approach including fracture mechanics. The enhanced materials processing knowledge gained through this project will help harness opportunities for effective designs and manufacturing of stronger engineering materials.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.