HYBRID DIMPLE-AND-VOID AUXETIC STRUCTURES WITH ENGINEERED PATTERNS FOR CUSTOMIZED NPR BEHAVIOR

Auxetic structures, low porosity auxetic sheets, systems and devices with auxetic structures, and methods of using and methods of making auxetic structures are disclosed. An auxetic structure is disclosed which includes an elastically rigid body with a plurality of apertures extending through the elastically rigid body and a plurality of protrusions projecting from the elastically rigid body. The apertures and protrusions are arranged in an engineered pattern, such as an array of rows and columns. The apertures are cooperatively configured with the protrusions to provide a predefined porosity while exhibiting stress reduction through negative Poisson's Ratio (NPR) behavior under macroscopic planar loading conditions. In some embodiments, the protrusions, which are elliptical or semispherical dimples, are interposed in square or hexagonal patterns with the apertures, which are S-shaped through slots or circular boreholes.