Functionally graded TPMS gyroid structures for additive manufacturing of non-pneumatic tires

Non-pneumatic tires (NPTs) have been of interest for extreme environmental applications involving uneven surfaces, such as military reconnaissance and space exploration. Despite the advantages over pneumatic tires, NPTs are unsuitable for mass production due to higher cost, increased weight, and more importantly, design and manufacturing complexities through traditional manufacturing methods. In this work, we present a novel NPT design that overcomes these challenges by incorporating additively manufactured (AM) minimal surface lattices in the elastic structure of the tire to provide structural stability in radial and lateral directions. More importantly, minimal surface lattices can be additively manufactured without the need for support materials. This enables on-demand manufacturing under extreme environments without the need for complicated machinery and human involvement. This study thoroughly examines the deformed shape and force-displacement behavior of spokes featuring cylindrically designed gyroid triply periodic minimal surface (TPMS) under vertical compression through both numerical simulations and experimental testing. The research evaluates three sub-scale NPTs with varying sheet thicknesses in the minimal surface layers, focusing on both global stiffness and local deformation. Digital image correlation (DIC) was used to provide detailed insights into the deformation behavior and local deformation characteristics of these lattices, laying design guidelines for designing variable stiffness in NPT that can be used for extreme conditions. Finite element analysis (FEA) is conducted to validate the experimental findings, demonstrating that the functionally graded TPMS with varying sheet thicknesses exhibits a 20 – 53% increase in stiffness compared to uniform thickness designs. This confirms the superior performance of the graded lattices over uniform-thickness NPTs. Findings from this study can be leveraged to further develop a design-AM workflow for tire performance of NPTs that could be deployed in uneven terrains through remote AM manufacturing.