Strain rate–dependent mechanical metamaterials

Abstract

Mechanical metamaterials are usually designed to exhibit novel properties and functionalities that are rare or even unprecedented. What is common among most previous designs is the quasi-static nature of their mechanical behavior. Here, we introduce a previously unidentified class of strain rate-dependent mechanical metamaterials. The principal idea is to laterally attach two beams with very different levels of strain rate-dependencies to make them act as a single bi-beam. We use an analytical model and multiple computational models to explore the instability modes of such a bi-beam construct, demonstrating how different combinations of hyperelastic and viscoelastic properties of both beams, as well as purposefully introduced geometric imperfections, could be used to create robust and highly predictable strain rate-dependent behaviors of bi-beams. We then use the bi-beams to design and experimentally realize lattice structures with unique strain rate-dependent properties including switching between auxetic and conventional behaviors and negative viscoelasticity.

Profusion of transition pathways for interacting hysterons

“…Third, metamaterials might yield physical realizations, with serially coupled mechanical hysterons naturally implementing antiferromagnetic interactions [27,31,33]. Finally, viscoelastic effects could be leveraged to obtain rate-dependent pathways and t-graphs and self-learning systems [36][37][38][39][40]. Together, progress on these questions will realize targeted pathways and information processing in designer materials.…”

Recent Progress in Active Mechanical Metamaterials and Construction Principles

“…Petryk [82] systematically summarized the material instabilities in elastic materials and plastic solids, which built a theoretical [86] Copyright 2020, American Association for the Advancement of Science. b) Porous metamaterials with tunable mechanical behaviors.…”

“…These large deformations and rotations result in large pattern transformations and mode switching of the structures, which could be widely utilized for the design of structural-instability-based metamaterials. Janbaz et al [86] bonded two kinds of materials with respectively hyperelastic and viscoelastic properties to prepare composite beams, which showed different deformation modes with the change of strain rates. Based on this, they used a predictable analytical model to explain the instability of the beams and constructed the complex strain rate-dependent systems (Figure 4a).…”

“…Metamaterials based on mechanical instability. a) Buckling deformation of double beam sensitive to strain rate [86]. Copyright 2020, American Association for the Advancement of Science.…”

Oligomodal metamaterials with multifunctional mechanics

“…To achieve this goal, we leave the realm of static responses and harness viscoelastic dissipation to tune the dynamical response of our metamaterial ( 26 – 28 ), previously applied to alter the direction of a mechanical mode ( 26 , 28 ). Instead, we now harness viscoelasticity to switch between modes altogether.…”