CAREER: Multiscale Optimization of Additively Manufacturable Spatially Varying Cellular Microstructures

蜂窝结构依靠固体材料和空隙的模式来实现高强度、轻重量和其他特性的理想组合。一个众所周知的例子是蜂窝结构，但一般来说，一个细胞结构可以由不同形状、大小和方向的细胞组成。蜂窝结构在许多应用中都很重要，包括轻型航空航天结构、生物医学设备、能量吸收器、热交换器和隔音。然而，优化设计细胞结构的一般技术仍然是一个挑战。该学院早期职业发展计划（Career）奖支持基础研究，以创造优化设计细胞结构的新技术，从而在特定工程应用中实现无与伦比的性能。该设计方法将允许细胞形状和大小在整个结构中以最佳方式变化，并将在优化过程中纳入与3D打印技术相关的制造限制。确定了两种应用来评估该方法并证明其对社会的益处：改进骨科植入物和轻型飞机机翼结构以提高能源效率。这个CAREER项目将通过动手演示、视觉工具、概念图和一个细胞设计计算机应用程序，将细胞结构设计和制造概念整合到互动学习计划中。针对从K-12到普通公众的受众，特别强调不同的未被充分代表的群体，教育计划包括四个组成部分：(1)教育工作者培训，(2)学生课外活动，(3)课程开发，(4)公众宣传。该奖项的理论和实验基础将允许从优化宏观结构的拓扑转向细胞微观结构的拓扑和形态，扩大设计灵活性，而不会对计算资源提出过多的要求。该项目为优化细胞微结构中的不连通性和制造优化设计中的均匀性水平等异常特征提供了新的基本理解。该研究的创新方面包括在优化过程中利用适应不同细胞类型的谐波分解来表示细胞配置，并在方法中实施细胞尺寸和长度尺度约束以确保制造可行性。通过模拟和实验测试，研究了优化后的细胞几何形状与力学性能和结构性能之间的关系。优化后的微结构将进行3D打印，并研究不同细胞类型和长度尺度的各种可制造性特征，如变形和粉末捕获。为了研究新型优化框架在不同设计要求下的有效性，将对骨科植入物的刚度和强度进行优化应用研究，并对具有八柱桁架内部支撑结构的蜂窝翼皮进行多学科设计优化。该奖项反映了美国国家科学基金会的法定使命，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。

Cellular structures rely on patterns of solid materials and voids to achieve desirable combinations of high strength, light weight and other properties. A well-known example of this is the honeycomb pattern, but in general a cellular structure can consist of cells with varying shape, size and orientation. Cellular structures are important in many applications, including light-weight aerospace structures, biomedical devices, energy absorbers, heat exchangers, and acoustic insulation. However, general techniques for optimally designing cellular structures remain a challenge. This Faculty Early Career Development Program (CAREER) award supports fundamental research to create new techniques for optimally designing cellular structures to achieve unrivaled performance for specific engineering applications. The design approach will permit cellular shape and size to vary optimally throughout the structure and will incorporate manufacturing constraints associated with 3D printing techniques in the optimization process. Two applications are identified to evaluate the methodology and demonstrate its benefit to society: improved orthopedic implants and lightweight aircraft wing structures for improved energy efficiency. This CAREER project will integrate cellular structure design and fabrication concepts into interactive learning plans through hands-on demonstrations, visual tools, concept-mapping, and a cellular design computer app. Aimed at audiences from K-12 to the general public, with specific emphasis on diverse underrepresented groups, the educational plan consists of four components: (1) educator training, (2) student extracurricular activities, (3) curriculum development, and (4) public outreach.The theoretical and experimental foundations of this CAREER award will allow a shift from optimizing the topology of macrostructures to topology and morphology of cellular microstructures expanding design flexibility without placing excessive demands on computational resources. This project provides new fundamental understanding of abnormal features such as disconnectivity in optimized cellular microstructures and the level of homogeneity in the fabricated optimized designs. Innovative aspects of the research include utilizing a harmonics decomposition that is adaptable to different cell types to represent the cellular configurations in the optimization process and implementing cell size and length scale constraints in the methodology to ensure fabrication feasibility. The relationships between the optimized cellular geometries and mechanical properties and structural performance are studied through simulation and experimental testing. The optimized microstructures will be 3D printed and various manufacturability characteristics such as deformation and powder trapping will be studied for different cell types and length scales. To investigate the effectiveness of the novel optimization framework for different design requirements, application studies will be performed on optimizing an orthopedic implant for stiffness and strength and multi-disciplinary design optimization of a honeycomb wing skin with octet truss internal support structures.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.