Fabrication and Testing of Z-Expandable Auxetic Textile Structures for Impact Protection

Abstract

Auxetics are counter-intuitive smart materials that grow in dimensions, perpendicular to the applied force. These are often used for impact protective clothing applications. The manufacture of 2D and 3D auxetics is generally complex. Both 2D and 3D auxetics grow perpendicular to the axis that is stretched. While 2D auxetics grow along the same plane, 3D auxetics could grow in one or more directions. Limited research has been directed towards the creation and testing of 2D to 3D transformable auxetics, based on buckling, twisting and pop-up mechanisms. In this study, three Z-expandable auxetic structures were manufactured from a sheet-like textile material, compared and analyzed. The stresses that come into play during growth and recovery were identified during tensile testing. A negative Poisson’s ratio for each confirmed auxeticity and results reveal that these structures are anisotropic. The structural parameters associated with the three structures were identified and analyzed mathematically.