An experimental and numerical study on an innovative metastructure for 3D printed thermoplastic polyurethane with auxetic performance

Metamaterials are specifically designed materials that possess unique properties that cannot be found in naturally occurring substances. These remarkable materials have the capability to bring about a significant transformation across a wide range of industries. Auxetic structures are a recent area of research possess a distinctive characteristic known as a negative Poisson's ratio. Unlike conventional materials that contract when stretched, auxetic structures actually expand in two dimensions. In this study, a new auxetic structure was introduced, and thermoplastic polyurethane samples were 3D printed using a fused filament fabrication method. The samples are then subjected to strains ranging from 5% to 50% and Poisson's ratios are measured both experimentally and numerically using finite element method in Ansys software. By comparing the results of the experimental research and simulation, it is evident that applying strains within this range causes the Poisson's ratio of the samples to change from -0.81 to -0.14 and it showed that the newly introduced structure is auxetic. According to the analysis of root mean square error, the hexagonal mesh with a size of 0.7 mm consistently produced the most accurate results, aligning closely with the experimental sample. Given that this is an entirely novel auxetic structure within the category of arrow-head auxetic structures, there is potential for future research to be conducted in order to further develop and enhance this model.