Uniaxial Tensile Properties of Flexible Auxetic Re-entrantHoneycomb Structures Made by 3D Printing

Engineers have vested interested in auxetic materials because of their negative Poisson's ratio. These materials undergo perpendicular expansion under tension. Meanwhile, auxetic textiles that has both flexibility and negative Poisson's ratio have great potential in future functional materials. In this paper, different flexible re-entrant honeycomb structures are manufactured using 3D printing technology. The shape change processes were also investigated. The re-entrant honeycomb structures exhibits negative Poisson's ratio immediately when stretched. The shape change consists of three stages in X1-direction, the same as that in X2-direction. A noticeable discovery was that the shape change in the X1-direction posed an out-plane change after the first shape change stage, while the shape change in X2-direction always remained in-plane throughout the entire tension process. The Young's moduli were also tested and were consistent with the tendency of the previous works' theoretical analysis.