The Institut für Kunststofftechnik (IKT) at the University of Stuttgart is investigating auxetic structures made of plastics. The focus here is on optimizing auxetic behavior in addition to the material blend of biodegradable materials. For this reason, polylactic acid (PLA) and polybutylene adipate terephthalate (PBAT) are used in their pure form, as well as several blends of the two materials, for the production of auxetic structures. The structures are tested for their auxetic behavior using tensile testing, and the results are compared with those of the simulations to enable parameterization of the simulations. This is essential due to the manufacturing process, fused filament fabrication (FFF), as residual stresses occur here that affect the properties of the manufactured parts. In the experiments, a structure consisting of inverse honeycombs is analyzed. This consists of hexagonal honeycombs in which two opposite corners are folded inwards into the honeycomb. The structure is suitable for analysis due to its relatively simple design, as there are no rotations of the structures and therefore buckling mainly occurs in the corners of the honeycombs. This simplifies angle measurement and due to that obtaining relative change in width orthogonal to the change in length. The results show that the evaluation of at least 5 × 5 inverse honeycombs is particularly suitable for demonstrating auxetic behavior. Above this number of cells, the displacements caused by forces applied to the structure are normalized to such an extent that the most inner inverse honeycomb is deformed in an ideally auxetic manner. Furthermore, it has been shown that a material specially developed for this application, a blend of the plastics PLA and PBAT, exhibits the best deformation properties. This material model is also used in the simulation to perform geometric optimizations on the inverse honeycomb geometry.