Person:

Shan, Sicong

Geometrical frustration arises when a local order cannot propagate throughout the space because of geometrical constraints. This phenomenon plays a major role in many systems leading to disordered ground-state configurations. Here, we report a theoretical and experimental study on the behavior of buckling-induced geometrically frustrated triangular cellular structures. To our surprise, we find that buckling induces complex ordered patterns which can be tuned by controlling the porosity of the structures. Our analysis reveals that the connected geometry of the cellular structure plays a crucial role in the generation of ordered states in this frustrated system.

Soft cellular structures that comprise a solid matrix with a square array of holes open avenues for the design of novel soft and foldable structures. Our results demonstrate that by simply changing the shape of the holes the response of porous structure can be easily tuned and soft structures with optimal compaction can be designed.

Soft materials can significantly change their shape and volume when subjected to various stimuli. Materials with deliberately designed periodic microstructure have long been proved to be characterized by properties that may exceed those of the corresponding bulk material. Though traditionally avoided as modes of failure, mechanical instabilities have recently been exploited to design systems with novel and tunable functionalities. Interestingly, the studies I conducted during my PhD show that the combination of soft materials, periodic structures, mechanical instabilities and large deformation give us the opportunity to design materials and structures with enhanced functionality. In this thesis, I present a systematic study on the response of planar sof୴ functional materials which use their large deformation and geometric rearrangements to dramatically change their properties. In particular, I used a combination of experiments and numerical simulations to investigate the effect of important parameters, such as pore shape, hole arrangement and loading conditions. With the fundamental understanding I gained, I developed a novel class of planar soft periodic materials with enhanced material functionalities such as tunable phononic band-gap, spontaneous symmetry breaking, chirality amplification and energy trapping. Remarkably, since the continuous 2D soft and porous structures I studied take advantage of reversible and scale-independent mechanisms, the proposed designs can be applied over a wide range of length scales. The studies presented here show that by mastering the interplay between the microstructure of soft periodic structures and their large deformation behavior, novel materials with enhanced func