Architected Materials with Ultra-Low Porosity for Vibration Control.

Periodic structures with extremely low porosities capable of forming large band gaps-frequency ranges with strong wave attenuation-are designed by patterning an elastic sheet with an array of alternating crack-like pores separated by small ligaments. The results indicate that the presence and size of the band gaps are controlled by the smallest geometric -feature in the system (which can be easily controlled by tuning the aspect ratio of the pores), providing an important guideline for the design of systems with the -desired response.

Dimpled elastic sheets: a new class of non-porous negative Poisson's ratio materials.

In this study, we report a novel periodic material with negative Poisson's ratio (also called auxetic materials) fabricated by denting spherical dimples in an elastic flat sheet. While previously reported auxetic materials are either porous or comprise at least two phases, the material proposed here is non-porous and made of a homogeneous elastic sheet. Importantly, the auxetic behavior is induced by a novel mechanism which exploits the out-of-plane deformation of the spherical dimples. Through a combination of experiments and numerical analyses, we demonstrate the robustness of the proposed concept, paving the way for developing a new class of auxetic materials that significantly expand their design space and possible applications.

Low porosity metallic periodic structures with negative Poisson's ratio.

Auxetic behavior in low porosity metallic structures is demonstrated via a simple system of orthogonal elliptical voids. In this minimal 2D system, the Poisson's ratio can be effectively controlled by changing the aspect ratio of the voids. In this way, large negative values of Poisson's ratio can be achieved, indicating an effective strategy for designing auxetic structures with desired porosity.