Multimaterial Approach to Improve the Mechanical Properties of a Novel Modified Auxetic Reentrant Honeycomb Structure

Auxetic materials are characterized by their negative Poisson's ratio, which also leads to several other beneficial properties. For example, a low density, high indentation resistance, and high energy absorption capacity enable applications in lightweight construction, ballistic protection, and shock absorption. A modified auxetic reentrant structure has previously been optimized to maximize its mass-specific energy absorption capacity for ideal usage in lightweight construction. Yet, the structure is only composed of a single-material, whereas, a multimaterial approach can improve its ability to exhibit auxetic deformation, if its vertical struts are composed of a material with a higher stiffness than the horizontal struts. Hence, the present contribution shows that the usage of multiple materials combined into the same structure leads to severe improvements of the overall performance. Therefore, quasi-static experiments are carried out on 3D-printed samples of a reentrant structure consisting of two different polymers and compared to each individual phase. Additionally, simulations are performed using LS-DYNA to get a deeper understanding of the deformation process. While the fabrication can be challenging, the characteristic deformation behavior is improved significantly, leading to a 50% lower Poisson's ratio as well as enhanced failure characteristics, which are especially noticeable through digital image correlation analysis.