Frustrated Metamaterials as Shape-Morphing Structures

该基金将支持对受挫折的机械超材料力学的研究，并将探索其作为大型结构的适用性。超材料是简单结构元件的组合，如梁和板，它们在一起产生极端的形状变化和其他非常规反应。周期性超材料的特点是低能量的变形模式，称为机制。在存在非周期性的情况下，相邻单元的变形之间的不相容性阻碍了机构。这些通常被看作是一个麻烦;在这个项目中，它们被接受来实现功能。实际上，在二维系统中，源自不相容性的几何“挫折”导致平面外屈曲，并且最初平坦的系统变形（字面上，弹出）成三维壳状物体。这项研究将创造二维超材料的挫折的起源和表现形式的知识，并将探索其作为具有以下独特属性的大规模可展开结构的适用性：（i）它们由于拉伸（而不是压缩）力而弹出;（ii）它们可以在没有地面锚固的情况下被预应力;（iii）它们可以准确地部署，因为所需的形状被编码在平坦的前体中。这个项目中的想法有可能彻底改变工程师设计可部署系统和架设轻质自由形式结构（如网格壳，大型圆顶和弹出式避难所）的方式。教育活动，围绕形状变形的主题为中心，课程开发和本科生赋权的基础上，将刺激结构工程专业的学生拥抱创造力，并重新审视他们的结构作为不变的，静态的实体先入为主的想法。该项目的主要目标是提供对各种非周期性超材料系统中几何挫折的系统理解，并利用这些知识实现创新的形状变形结构。第一步是通过理论、实验和数值方法阐明面内阻挫的先决条件。注意力将致力于驱动的位置和幅度之间的相互作用，超材料的架构，以及易于屈曲的压缩区域的位置。将利用降阶数值模型预测平面外形状过渡。还将采取步骤来制定机械逆向设计，即，以找到获得目标三维形状所需的平面内结构以及致动力的位置和范围。最后，挫折的原则，最初通过桌面规模的原型研究，将被转化为大规模。本文将通过实验和数值模拟研究异向材料诱导的阻挫结构的可展开性和承载能力。 一门关于变形的新课程正在计划中。 本科生和研究生都将被培养为新一代的“结构思考者”。“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 will support research on the mechanics of frustrated mechanical metamaterials and will explore their applicability as large-scale structures. Metamaterials are assemblies of simple structural elements like beams and plates that, in concert, yield extreme shape transformations and other unconventional responses. Periodic metamaterials feature low-energy modes of deformation called mechanisms. In the presence of non-periodicity, mechanisms are impeded by incompatibilities between the deformations of neighboring units. These are usually seen as a nuisance; in this project, they are instead embraced to achieve functionality. Indeed, in two-dimensional systems, the geometric “frustration” stemming from incompatibilities results in out-of-plane buckling, and the initially flat system morphs (literally, pops-up) into a three-dimensional shell-like object. This research will create knowledge on the origin and manifestation of frustration in two-dimensional metamaterials and will explore their applicability as large-scale deployable structures with the following unique attributes: (i) they pop-up due to tensile (rather than compressive) forces; (ii) they can be prestressed without ground anchoring; (iii) they can be accurately deployed since the desired shape is encoded within the flat precursor. The ideas within this project have the potential to revolutionize how engineers think about designing deployable systems and erecting lightweight freeform structures like gridshells, large domes, and pop-up shelters. The educational activities, centered around the theme of shape morphing and based on both curriculum development and undergraduate student empowerment, will stimulate structural engineering students to embrace creativity and to revisit their preconceived idea of structures as non-changing, static entities. The primary objective of this project is to provide a systematic understanding of geometric frustration in various non-periodic metamaterial systems, and to exploit this knowledge to realize innovative shape-morphing structures. The first step will be to elucidate the in-plane prerequisites to frustration via theoretical, experimental, and numerical means. Attention will be devoted to the interplay between the location and magnitude of the actuation, the metamaterial’s architecture, and the location of the compressive regions prone to buckling. Reduced-order numerical models will be leveraged to predict out-of-plane shape transitions. Steps will also be taken to formulate a mechanistic inverse design, i.e., to find the in-plane architecture and the location and extent of the actuating forces necessary to obtain a target three-dimensional shape. Finally, the principles of frustration, initially studied via tabletop-scale prototypes, will be translated to large scales. The deployability and load bearing capacity of metamaterial-inspired frustrated structures will be investigated via experiments and numerical simulations. A new course on shape-shifting is planned. Both undergraduate and graduate students will be trained as the new generation of "structures thinkers."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.