Speaker: Prof. Hussein Nassar

Abstract

Periodic trusses are useful models of several materials such as foams, crystals and metamaterials. When the truss has poor connectivity, it exhibits a number of mechanisms, i.e., deformation modes that cost little to no elastic energy. While catastrophic in many cases, mechanisms can still be desirable. In this talk, we explore how mechanisms induce an array of peculiar behaviors in trusses and truss-based materials by strongly breaking some of the fundamental symmetries of elasticity theory: stress symmetry, mirror symmetry and parity symmetry. To motivate the study, we describe how trusses with mechanisms enable a theory of transformation elasticity, as potent as transformation optics and transformation acoustics. In particular, we show how trusses with mechanisms make perfect "invisibility” cloaks for elasticity.

Biography

Hussein Nassar is an Assistant Professor of Mechanical and Aerospace Engineering at University of Missouri, Columbia. He studied Engineering at École des Mines de Paris and Mathematics at Université Paris VI. He obtained a PhD in Mechanics from Université Paris-Est Marne-La-Vallée in 2015. He worked as a postdoctoral fellow at École des Ponts et Chaussées and then at University of Missouri where he became a faculty member in 2018. His research interests are in the areas of elasticity, wave motion, homogenization and geometry. His activities are supported by the National Science Foundation and by the Army Research Office.

References

• H. Nassar, Y. Chen, G. L. Huang.
  Polar Metamaterials: A New Outlook on Resonance for Cloaking Applications,
  Phys. Rev. Lett. 124, 084301, 2020.


• H. Nassar, H. Chen, G. L. Huang.
  Microtwist elasticity: A continuum approach to zero modes and topological polarization in Kagome lattices,
  arXiv preprint, arXiv:2004.01699, 2020.

Document compiled by Camille Guévenoux.