Collaborative Research: Controlling the Microstructure for Improved Mechanical Properties of Large-scale Polymer Composite Structures Made by Big Area Additive Manufacturing

该补助金支持有助于与制造过程相关的新知识的研究，从而促进科学进步，国家繁荣和国防。增材制造，通常称为三维打印，是一种从数字计算机模型制作几乎任何形状的方法。 虽然桌面三维打印机已经变得相当流行，但它们通常限于较小的物体，没有足够的强度用于结构应用。 这项研究的重点是一种相对较新的增材制造，能够制造大型结构，如全尺寸的汽车和房屋。 该项目进行基础研究，以更好地了解挤压碳纤维增强聚合物材料的大面积增材制造（BAAM），以生产可用于汽车，航空航天，能源，建筑和国防部门的更高强度部件。 这是两所大学之间的一项合作研究工作，使包括女性和少数民族在内的广泛而多样化的学生群体接触新的制造技术，并提供参与实践活动的机会，鼓励他们在STEM相关领域从事职业生涯。虽然大规模聚合物结构的大面积增材制造（BAAM）的发展迅速，对挤出的纤维增强聚合物复合材料内的独特微结构的基本理解还没有跟上。最近改善3D打印材料机械性能的大多数努力都集中在界面性能和解决细观结构缺陷，例如由于不完全填充而导致的珠粒之间的空隙。 然而，通过控制挤出珠的内部微观结构来改善3D打印结构的机械性能有很大的机会。 具体而言，本研究的目标是通过控制增强纤维和空隙的尺寸、取向和分布来最大化挤出聚合物复合材料的机械性能，所述增强纤维和空隙限定其内部微观结构。 这是通过改变单螺杆挤出机内的流动路径和产生的剪切应变场以及优化加工参数如流速、压力和温度曲线来实现的。研究任务旨在建立新的有限元模型的沉积流动的聚合物熔体通过螺杆和喷嘴，除了本构模型定义的微分方程，提供独特的洞察纤维取向，空隙形成，纤维断裂和颗粒迁移过程中的处理。 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 grant supports research that contributes to new knowledge related to a manufacturing process, thus promoting the progress of science, national prosperity, and national defense. Additive manufacturing, more commonly known as three-dimensional printing, is a method of making virtually any shape from a digital computer model. Although desktop three-dimensional printers have become quite popular, they are often limited to smaller objects without sufficient strength for structural applications. This research focuses on a relatively new class of additive manufacturing that is capable of making large-scale structures such as full-size cars and houses. This project conducts fundamental research to better understand big area additive manufacturing (BAAM) of extruded carbon-fiber reinforced polymer materials to produce higher strength components that can be used in the automotive, aerospace, energy, construction and defense sectors. This is a collaborative research effort between two universities that exposes a wide and diverse group of students, including women and minorities, to new manufacturing technologies and provide opportunities to engage in hands-on activities that encourage them to pursue a career in STEM-related fields.While the development of big area additive manufacturing (BAAM) of large-scale polymer structures has moved quickly, a basic understanding of the unique microstructure within an extruded fiber-reinforced polymer composite has not kept pace. The majority of recent efforts to improve the mechanical performance of 3D-printed materials has focused on interfacial properties and addressing meso-structural defects, such as voids between beads due to incomplete filling. However, there are significant opportunities for improving the mechanical performance of 3D printed structures by controlling the internal microstructure of the extruded bead. Specifically, the goal of this research is to maximize the mechanical performance of an extruded polymer composite by controlling the size, orientation, and distribution of reinforcing fibers and voids that define its internal microstructure. This is accomplished by altering the flow path and resulting shear strain fields within the single-screw extruder and optimizing processing parameters such as flow rate, pressure, and temperature profile. Research tasks seek to establish new finite element models for deposition flow as polymer melt passes through the screw and nozzle, in addition to constitutive models defined by differential equations that provide unique insight into fiber orientation, void formation, fiber breakage and particle migration during processing. The resulting knowledge and database of material properties enable the printing of tailored microstructures within BAAM parts and components.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.