GALCIT Colloquium

Buckling of structures has been explored for over two centuries. Recent interests in soft materials and architected materials have revitalized the field. Soft materials are often subjected to high strain, presenting nonlinear and non-equilibrium behavior, and tend to buckle into distinctive modes or patterns. On the other hand, architected materials show unusual mechanical properties and functions that are difficult or impossible to achieve in homogeneous materials. Embedding components that are vulnerable to buckling into architected materials is one of the most effective strategies to tailor their constitutive behavior and enable new functionalities. In this talk, unconventional column and shell buckling is investigated, and integrated into architected materials for functions. First, we discover that subjected to an axial compression, a soft hyperelastic column with a high width-to-length ratio can discontinuously buckle, snapping from one stable equilibrium state to another. Such a snapping buckling induces energy dissipation, but is completely recoverable. Making use of these properties, we develop a reusable, self-recoverable, and rate-independent energy-absorbing architected material by stacking layers of wide hyperelastic columns. Next, we characterize and model the pseudo-bistability of viscoelastic shells, i.e. a viscoelastic shell can stay inverted when pressure is removed, and snap to its natural shape after a delay time. We establish a viscoelastic shell theory to explain the mechanism and stability evolution of the pseudo-bistable behavior. By assembling such shells with different recovery time into arrays, we achieve spatiotemporally programmable and reconfigurable metasurfaces under simple pneumatic actuation. Finally, we demonstrate woven shells with unique and tunable buckling behavior as architected materials. Our work provides fundamental insights into unconventional column and shell buckling, and opens up new avenues in designing functional architected materials.