Thursday, 21 January 2021

Speaker: Prof. Dennis Kochmann

Institute of Mechanical Systems – ETH Zürich

Spinodoids – cellular architectures with intriguing properties

Abstract

Tailoring the architecture of cellular materials – from random foams to periodic structures based on trusses, plates,and shells – has resulted in a variety of lightweight architected materials with beneficial mechanical properties. While periodic networks offer advantages such as a simple effective property extraction, they come with significant shortcomings including the sensitivity to symmetry-breaking defects, challenges and limitations arising from spatial unit cell variations, and non-scalable fabrication techniques. So-called spinodal architectures, by contrast, are non-periodic and show little sensitivity to defects, and they evolve naturally during diffusion-driven self-assembly processes. Inspired by spinodal architectures found in nature, we introduce spinodoid topologies as an efficient theoretical description of “spinodal-like” structures. Spinodoids follow a simple mathematical parametrization and have intriguing mechanical properties such as optimal stiffness scaling with density as well as a superb resilience due to their curvature distribution. They further cover an enormous anisotropic property space in a seamless fashion, which enables spatially graded structures with locally optimized mechanical properties and multiscale topology optimization of engineering structures. Moreover, we present experimental prototypes of spinodoid architectures and demonstrate their mechanical resilience. Finally, we address the inverse challenge of identifying a microstructural architecture from the huge design space to achieve a sought combination of macroscale properties. We demonstrate that a data- driven approach based on the integration of two neural networks for the forward- and inverse-problems renders the challenge well-posed and reliably and accurately generates foam-type cellular metamaterials with as-designed 3D anisotropy and density in a spatially uniform or functionally graded fashion. As a particular example, we highlight the suitability of this new approach for the generation of bio-mimetic bone replacements.



Biography

Dennis Kochmann received his education at Ruhr-University Bochum and at the University of Wisconsin- Madison. He was a postdoc and Fulbright fellow at Wisconsin and a Feodor Lynen fellow at Caltech, before joining the Aerospace Department at Caltech as Assistant Professor in 2011. From 2016 to 2019 he was Professor of Aerospace at Caltech. Since April 2017 he has been Professor of Mechanics and Materials at ETH Zürich, where he served as Head of the Institute of Mechanical Systems and is currently Deputy Head of the Department of Mechanical and Process Engineering. His research focuses on the link between structure and properties of a variety of materials and metamaterials, which includes the development of theoretical, computational and experimental methods to bridge across scales from nano to macro. His research has been recognized by, among others, the Bureau Prize in Solid Mechanics form IUTAM, the Richard von Mises Prize by GAMM, an NSF CAREER Award, the T.J.R. Hughes Young Investigator Award by the ASME, and an ERC Consolidator Grant.


Notes

by Benjamin Dieu and Chloé Giraudet

Suggested readings

LMS seminars on related topics