Fabrication and property of auxetic warp-knitted spacer structures with mesh

For the purpose of reconstructing a three-dimensional auxetic structure adopting spacer warp-knitting techniques, a simple mathematical model based on the structure of auxetic warp-knitted spacer hexagonal meshes was established and several samples were produced using an E22 RD7/2-12EN warp-knitting machine. It is predicted from synthesizing the results of both mathematical modeling and experimental sampling that auxetic performance of this structure mainly depends on the contraction distortion before stretching in three directions, especially in the y-axis. When it comes to knitting parameters, yarn fineness, machine gauge, fabric density, movement of guide bars, and inclination angle of wales all matter for the auxetic performance, which is also affected by the stiffness of materials and the lodging of spacer yarns. It is also concluded that successive inlaying in the same direction of the spacer guide bar favors contraction distortion in the y-axis, which means auxetic performances can be more easily achieved in this way.