Projects

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. 

Research Article: https://doi.org/10.36922/msam.5022 

The ability to manufacture complex design geometries via Additive Manufacturing (AM) has led to a rapid growth in advancing the design methods, fabrication, and application of Triply Periodic Minimal Surface (TPMS) lattices with minimal surface topologies. Due to its zero-mean curvature, TPMS lattices can be additively manufactured without any sacrificial support structures and offer both design and manufacturing engineers unprecedented control over the physical properties (surface area, relative density, etc.) and mechanical properties (flexural strength, Young's modulus, etc.). TPMS lattices are of high interests for a wide range of applications including; biomedical implants, energy absorption, and surface fluidic applications such as heat exchangers, and energy storage. Recent advancements in functionally graded TPMS lattice design by varying local lattice geometry has shown to result in different mechanical performance. However, there has been limited studies in understanding the functional grading of AM process conditions (e.g., Laser-Powder Bed Fusion in this study) and lattice sheet thickness to map the design-processing conditions-properties. The goal of this study is to achieve similar mechanical properties in TPMS sheet lattices with two different TPMS sheet thicknesses by varying laser processing conditions (e.g., contour and hatch conditions in this study). Quasi-static tensile testing of solid samples with corresponding AM conditions and 3-point bending tests of TPMS lattices were performed in accordance to ASTM E8 and ASTM E290, respectively. It was observed that the flexural properties of the 0.75mm and 0.25 mm TPMS lattices vary with different scan strategies and speed variations. This could be attributed to the varying laser-powder interactions particularly in thin wall TPMS lattices under contour-only and hatch-only laser scanning strategies. Also, the 0.75 mm TPMS sheet lattices exhibited 79% higher flexural stiffness than the 0.25mm sheet lattices. It was also observed that this observed trend was reversed in the case of tensile properties. Findings from this study can provide new directions towards achieving gradient TPMS lattice designs with varying local mechanical performance by grading the laser scanning strategies to achieve desired mechanical properties and surface topologies.

Research Article: https://doi.org/10.1016/j.mfglet.2024.09.129