CAREER: The Mechanics of Tunable Exoskeleton Structures: Interactions of Rigid Scales with Deformable Substrates

这项教师早期职业发展（Career）资助将发现生物外骨骼结构复杂机械行为的基础。为了满足人机一体化机器人、老化基础设施检测、损伤康复等日益增长的工业需求，外骨骼的行为和设计理解需要取得突破。最基本的外骨骼结构包括一个相对柔软的基底和一排较硬的，从基底伸出的鳞片作为外骨骼。当基座变形时，这些嵌入的尺度也会变形，它们相互碰撞和滑动，导致非线性机械响应和多功能的出现，这在传统材料中通常是不可能的。本研究项目旨在通过分析技术、多尺度计算模型和实验验证来理解和量化这种结构-性能相互作用。此外，教育和推广计划还包括几项努力：通过机构STEM中心纳入代表性不足的学生，作为大学STEM日的一部分，举办名为RoboTales的独特科技科幻活动，并通过大都会科学中心的“现代机器”之夜活动参与公共教育。本研究的目的是量化在外骨骼结构的代表性类别中运作的结构-性质关系，并发现普遍和紧急的极端行为。先前的研究表明，在柔软的、最初平坦的基片上，刚性仿生鳞片在弯曲和扭转模式下都会产生应变硬化，直到达到刚性“锁定”状态。然而，对于这些结果在类光束基底之外的普遍性知之甚少，这限制了它们的应用。因此，PI有两个假设：(a)存在普遍的运动锁定-跨越几何，变形模式和序列的刚性锁定行为；(b)极端紧急行为-多轴非线性响应的出现，手性和各向异性演化的对称性破缺，以及局部锁定模式。这些假设的测试将通过开发新的能力来实现：(i)几何精确的非线性弹性模型，（ii）多尺度有限元模型，包括均匀化模型，跨越外骨骼尺度（微观）和基底变形（宏观），以及（iii）主动外部架构多材料系统的力学。选定的三维数字图像相关实验将提供进一步的数据理解和验证。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。

This Faculty Early Career Development (CAREER) grant will discover the fundamentals of the complex mechanical behavior of bioinspired exoskeleton structures. Breakthroughs in the understanding of behavior and design of exoskeletons are needed to fulfill the growing industrial needs of human-integrated robotics, inspection of aging infrastructure, injury rehabilitation, etc. The most elementary of exoskeleton structures consists of a relatively soft base and an array of stiffer, protruding scales from the base serving as the exoskeleton. As the base deforms, so do these embedded scales, which collide and slide against each other leading to the emergence of nonlinear mechanical response and multi-functionality, not typically possible in traditional materials. This research project aims to understand and quantify this structure-property interplay with the help of analytical techniques, multi-scale computational modeling, and experimental validation. Additionally, the education and outreach plan includes several efforts: inclusion of underrepresented students via an institutional STEM center, a unique technology-science fiction event named RoboTales as part of university’s STEM day, and participation in public education via the ‘modern machines’ night event at the Metropolitan Science Center.The objective of this research is to quantify the structure-property relationships operative in a representative class of exoskeletal structures and discover universal and emergent extreme behavior. Prior work has shown that the rigid biomimetic scales on soft, initially flat substrates give rise to strain stiffening in both bending and twisting modes until a rigid ‘locking’ state is reached. However, little is known about the generality of these results beyond beam like substrates, limiting their application. Therefore, the PI has two hypotheses: (a) existence of universal kinematic locking–rigid locking behavior across geometry, deformation modes, and sequence and (b) extreme emergent behavior–emergence of multiaxial nonlinear response, broken symmetry with evolution of chirality and anisotropy, and localized locked modes. Testing of these hypotheses will be achieved via development of new capabilities: (i) geometrically exact nonlinear elasticity models, (ii) multi-scale finite element models, including homogenization models, spanning the exoskeleton scales (micro) and the substrate deformation (macro), and (iii) mechanics of active externally architected multi-material systems. Selected experiments with 3D digital image correlation will provide further data for understanding and validation.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.