Tensile and bending properties of flexible auxetic re-entrant honeycombstructures made by 3D printing

The main content dealt with in the paper was to present a flexible auxetic re-entrant honeycomb fabric, which was made of a formulated thermoplastic polyurethane material PolyFlex with super elastic properties by 3D printing technology. The auxetic fabric shows perpendicular expansion under tension and is flexible. So, its special property makes auxetic fabric have great potential in future functional materials. Wherein, the honeycomb cell angle is a key factor affecting Poisson’s ratio of fabric. In this paper, flexible re-entrant honeycomb structures with different cell angle are manufac- tured using 3D printing technology. The shape change under tension of two directions were investigated. The re-entrant honeycomb structures presented negative Poisson’s ratio immediately when stretched. The shape change consisted of three stages in X 1 -direction, the same as that in X 2 -direction. A noticeable discovery was that the shape change in X 1 -direction posed an out-plane change after the first shape change stage, while the shape change in X 2 -direction always remained in-plane in the whole tension process. The tensile modulus tested was consistent with the tendency of theoretical analysis of previous work. The bending rigidities were tested and similar to fabrics of poplin and denim. The results indicate that the auxetic fabric is suitable for special clothing.