CAREER: The Mechanics of Hierachically Multistable Metastructures

该学院早期职业发展（CAREER）补助金将支持研究一类新的材料系统的力学表现出内在的重塑和性能适应。传统的工程材料具有固定的宏观性质，这些性质来自特定的原子组成。与表现出许多非常规和随时间变化的特性（如固有的自我塑造）的生物系统相比，这限制了可用的设计可能性。这种生物学特征可归因于独特的微观结构，包括跨越几个长度尺度的分层几何排列。一个独特的几何特征，使属性适应是多稳态;即一个系统的能力，表现出几个共存的状态。追求这一概念，本研究的目的是获得模型，利用（本地）多稳态安排，或元结构，显示宏观适应性的变化，在当地规模。了解这种多稳态结构的力学将促进与航空航天，生物医学和机器人工业相关的先进结构和机器人材料的发展。这将扩大美国的科技优势，最终造福于整个经济和社会。此外，这项工作的多学科（工程和材料科学）性质允许促进STEM教育。这是追求通过建立多学科内容的课程教学策略，并提供设计经验的本科生和研究生partnering.The分层多稳态的材料系统的新概念，需要多个共存的全局配置的局部（多稳态）状态的单一组合的外观，从而打破了一对一的对应关系的局部和全局状态之间常见的多稳态超材料。这个项目的目的是了解负责分层多稳定性的表现的基本力学。具体来说，这项工作的目的是确定本地（单元格）和全球（元结构）的相互作用机制负责的外观分层多稳态。中心的假设是，在应变场的长程效应发展顺应变形模式的亚结构，由于在单位尺度的状态变化引入的局部扭曲。基于这一假设，本研究从考虑最近邻耦合出发，旨在推导出单胞之间的长程相互作用模型。分层多稳态的特性为设计耦合传感、计算和特性自适应的可编程结构开辟了新的途径。由此产生的亚结构与航空航天、生物医学和机器人工业有关。此外，这项工作的结果被用来制定教育计划，以鼓励多学科STEM教育和研究：1）与普渡大学的EPICS计划合作提供多学科设计经验;和2）该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准。

This Faculty Early Career Development (CAREER) grant will support research investigating the mechanics of a new class of material systems exhibiting intrinsic reshaping and property adaptation. Conventional engineering materials have fixed macroscopic properties that are derived from specific atomic compositions. This limits the available design possibilities when compared to biological systems that exhibit many unconventional and time-varying properties, like inherent self-shaping. This biological characteristic can be attributed to unique microstructures comprising hierarchical geometrical arrangements, spanning several length scales. A unique geometrical characteristic enabling property adaptation is multistability; i.e. a system’s capacity to exhibit several coexisting states. Pursuing this concept, this research aims to derive models to harness (locally) multistable arrangements, or metastructures, that display macroscopic adaptability from changes at the local scale. Understanding the mechanics of such multistable structures will facilitate the development of advanced structures and robotic materials relevant to the aerospace, biomedical and robotics industries. This will expand the U.S. scientific and technological edge, ultimately benefiting the economy and society at large. Furthermore, this effort’s multidisciplinary (engineering and material science) nature allows for promoting STEM education. This is pursued by establishing teaching strategies for courses with multidisciplinary content and offering design experiences partnering undergraduate and graduate students.The novel concept of hierarchical multistability in material systems entails the appearance of multiple coexisting global configurations for a single combination of local (multistable) states, thereby breaking the one-to-one correspondence between local and global states commonly found in multistable metamaterials. The objective of this project is to understand the fundamental mechanics responsible for the manifestation of hierarchical multistability. Specifically, this effort aims to determine the local (unit-cell) and global (metastructural) interaction mechanisms responsible for the appearance of hierarchical multistability. The central hypothesis is that long-range effects in the strain field develop compliant deformation modes in the metastructure due to local distortions introduced from changes of state at the unit scale. Building on this hypothesis and departing from considering nearest-neighbor coupling, this research aims to derive long-range interaction models between unit cells. The characteristics of hierarchical multistability opens novel avenues for designing programmable structures that couple sensing, computation and property adaptation. The resulting metastructures are relevant to the aerospace, biomedical and robotic industries. Furthermore, the results from this effort are leveraged to develop an educational plan to encourage multidisciplinary STEM education and research by: 1) offering multidisciplinary design experiences partnering with Purdue University’s EPICS program; and 2) establishing pedagogical strategies for teaching courses with multidisciplinary content.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.