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

The University Of Central Florida Board Of Trustees, Orlando FL

Investigators

Abstract

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.