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Materials Science in Additive Manufacturing Gyroid non-pneumatic tires through additive manufacturing

of four-point loaded beams, indicating that functionally thickness. To this end, we present a methodology for
graded lattices greatly improve flexural stiffness and experimentally testing the sub-scale tires and characterize
energy absorption, while also reducing crack propagation their performance according to their stiffness. Each design
and shear-band failure. Al-Ketan et al. and Yang et al. is built to elastically deform near the contact area while
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investigated the deformation behavior of 1D functionally maintaining good stiffness characteristics. The NPT designs
graded gyroid structures under various loading directions, had varying thicknesses, which would lead to different
finding that these structures demonstrated enhanced stiffness. Digital image correlation (DIC) was employed to
energy absorption capabilities only when the loading assess and compute the localized deformation of the four
direction aligned with the gradient. Zhang et al. found TPMS bands designed within each tire. This facilitated an
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that, compared to uniform sheet and skeletal TPMS, understanding of the deformation characteristics across
functionally graded structures exhibited improved various tires, offering valuable insights for the functional
mechanical stability, energy absorption, and better failure grading of tires utilizing TPMS-gyroid. The bulk
modes and strain distribution, offering insights into the stiffness was subsequently determined through analytical
mechanical deformation mechanisms of graded TPMS. calculations, utilizing the data acquired from quasi-static
compression testing. Furthermore, finite element analysis
This serves as a motivation for this study, where
the challenges associated with current NPT material (FEA) was conducted to validate the experimental results.
structures could be addressed by functionally graded Finally, the results are discussed, highlighting how varying
TPMS structures manufactured using AM. Before fully sheet thickness in TPMS-based NPT designs enables
evaluating the material behavior of AM-made NPTs, this precise control of local and global stiffness which enhances
study focuses on the large-scale production of airless load distribution and supports on-demand manufacturing
tires and a thorough understanding of the mechanical for applications in extreme environments, such as space
exploration.
properties of the sub-scale designs of these AM lattice tires.
In the current literature, very few research studies explore 2. Methods
the application of TPMS design for NPTs. Kim et al. 45,46
demonstrated that the rotated primitive-type auxetic 2.1. Tire construction and manufacturing
structure (RPAS) for airless tire spokes offers superior The novel tire design (Figure 1) uses a TPMS lattice that
stiffness and stability under compression compared to supports the outer tire tread and connects it to the inner
conventional NPT spokes designs. However, the variation rim. Sub-scale models of the tire design were modeled
in local stiffness of TPMS NPT tires under load conditions using nTopology (nTopology Inc., United States of America
across different designs remains poorly understood. In [USA]). Four layers of TPMS lattices were incorporated
addition, a tire with a single stiffness value may struggle to between the tread and the hub. A TPMS gyroid lattice was
satisfy the diverse performance requirements.
To this extent, this paper explores three different sub-
scale AM-made NPT gyroid tire concepts with varying sheet
thickness manufactured using a digital light processing
(DLP)-based AM process. 47-49 The overarching goal of the
study is to understand the local deformation and stiffness
of gradient TPMS gyroid bands, which would enable the
design of structures with varying thicknesses and tailored
deformation characteristics near the contact patch without
compromising the overall bulk stiffness. This approach
would allow for the design and manufacturing of TPMS
bands with different thicknesses and design strategies that
achieve local tunable stiffness which would be beneficial
for NPTs in rough terrain applications.

This study hypothesizes that by understanding the
local deformation in AM TPMS gyroid NPTs, better
control of mechanical response in tires can be achieved Figure 1. Computer-aided design model of the triply periodic minimal
surface gyroid tire with varying sheet thickness (1 – 2 mm). The
by radially grading the sheet thickness based on specific regions L0, L1, L2, and L3 represent areas of localized sheet thickness
stiffness requirements, loading conditions, and material variation, with each label corresponding to increasing thickness levels
volume constraints, compared to using a uniform sheet from L0 to L3

Volume 3 Issue 4 (2023) 3 doi: 10.36922/msam.5022