Auxetic Structures With Distorted Projection Slots In Engineered Patterns To Provide NPR Behavior And Improved Stress Performance

Abstract

Auxetic structures, effusion-cooling 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 opposing top and bottom surfaces. First and second pluralities of elongated apertures extend through the elastically rigid body from the top surface to the bottom surface. The first plurality of elongated apertures extends transversely with respect to the second plurality of elongated apertures. The first and/or second pluralities of elongated apertures have distorted shapes projected through the elastically rigid body at an oblique angle. The elongated apertures are cooperatively configured to provide a desired stress performance while exhibiting negative Poisson's Ratio (NPR) behavior under macroscopic planar loading conditions. By way of example, the auxetic structure may exhibit a reduction in stress concentration proximate the elongated apertures and a Poisson's Ratio of approximately −0.0001 to −0.9%.

1 . An auxetic structure comprising:
 an elastically rigid body with opposing top and bottom surfaces and first and second pluralities of elongated apertures extending through the elastically rigid body from the top surface to the bottom surface, the first plurality of elongated apertures extending transversely with respect to the second plurality of elongated apertures, each aperture of the first plurality of elongated apertures having a distorted shape projected through the elastically rigid body at an oblique angle,   wherein the first and second pluralities of elongated apertures are cooperatively configured to provide a desired stress performance while exhibiting a desired negative Poisson's Ratio (NPR) behavior under macroscopic planar loading conditions.   
     
     
         2 . The void structure of  claim 1 , wherein each aperture of the first plurality of elongated apertures is angled approximately 40-75 degrees with the top surface of the elastically rigid body. 
     
     
         3 . The void structure of  claim 1 , wherein a projection vector of each aperture of the first plurality of elongated apertures is at least substantially parallel to a direction of loading of the elastically rigid body. 
     
     
         4 . The void structure of  claim 1 , wherein each aperture of the second plurality of elongated apertures has a distorted shape projected through the elastically rigid body at an oblique angle. 
     
     
         5 . The void structure of  claim 4 , wherein a projection vector of each aperture of the second plurality of elongated apertures is at least substantially parallel to a direction of loading of the elastically rigid body. 
     
     
         6 . The void structure of  claim 1 , wherein the desired stress performance includes a reduction in stress concentration proximate the plurality of elongated apertures. 
     
     
         7 . The void structure of  claim 1 , wherein the NPR behavior includes a Poisson's Ratio of about −0.0001 to about −0.9%. 
     
     
         8 . The void structure of  claim 1 , wherein the elongated apertures have a predetermined porosity of about 0.3 to about 9%. 
     
     
         9 . The void structure of  claim 1 , wherein the elongated apertures are engineered with a predefined porosity, a predetermined pattern, or a predetermined aspect ratio, or any combination thereof, to achieve the NPR behavior. 
     
     
         10 . The void structure of  claim 1 , wherein each of the elongated apertures has an aspect ratio of approximately 5-40. 
     
     
         11 . The void structure of  claim 1 , wherein the first or the second plurality of elongated apertures, or both, each has an S-shaped plan-view profile. 
     
     
         12 . The void structure of  claim 11 , wherein the first and second pluralities of elongated apertures are arranged in an array of rows and columns. 
     
     
         13 . The void structure of  claim 12 , wherein the rows are equally spaced from each other and the columns are equally spaced from each other. 
     
     
         14 . The void structure of  claim 1 , wherein each of the elongated apertures has a major axis perpendicular to a minor axis, the major axes of the first plurality of elongated apertures being substantially perpendicular to the major axes of the second plurality of elongated apertures. 
     
     
         15 . An effusion-cooling auxetic sheet structure comprising:
 a metallic sheet with opposing top and bottom surfaces and first and second pluralities of elongated apertures extending through the metallic sheet from the top surface to the bottom surface, the first plurality of elongated apertures having a first set of geometric characteristics and a first pattern, the second plurality of elongated apertures having a second set of geometric characteristics and a second pattern, the first plurality of elongated apertures being orthogonally oriented with respect to the second plurality of elongated apertures, the elongated apertures having distorted shapes projected through the elastically rigid body at an oblique angle, wherein the first geometric characteristics and pattern of the first plurality of elongated apertures are cooperatively configured with the second geometric characteristics and pattern of the second plurality of elongated apertures to provide a desired stress performance while exhibiting negative Poisson's Ratio (NPR) behavior under macroscopic planar loading conditions.   
     
     
         16 . A method of manufacturing an auxetic structure, the method comprising:
 providing an elastically rigid body with opposing top and bottom surfaces;   adding to the elastically rigid body a first plurality of apertures extending through the elastically rigid body from the top surface to the bottom surface, the first plurality of apertures being arranged in rows and columns, each aperture of the first plurality of elongated apertures having a distorted shape projected through the elastically rigid body at an oblique angle; and   adding to the elastically rigid body a second plurality of apertures extending through the elastically rigid body from the top surface to the bottom surface, the second plurality of apertures being arranged in rows and columns,   wherein the first and second pluralities of apertures are cooperatively configured to provide a desired stress performance while exhibiting a negative Poisson's Ratio (NPR) behavior under macroscopic planar loading conditions.   
     
     
         17 . The method of  claim 16 , wherein each aperture of the first plurality of elongated apertures is angled approximately 40-75 degrees with the top surface of the elastically rigid body. 
     
     
         18 . The method of  claim 16 , wherein a projection vector of the first plurality of elongated apertures is at least substantially parallel to a direction of loading of the elastically rigid body. 
     
     
         19 . The method of  claim 16 , wherein each aperture of the second plurality of elongated apertures has a distorted shape projected through the elastically rigid body at an oblique angle. 
     
     
         20 . The method of  claim 19 , wherein a projection vector of the second plurality of elongated apertures is at least substantially perpendicular to a direction of loading of the elastically rigid body. 
     
     
         21 - 29 . (canceled)