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

relationship between increased sheet thickness and global 4.3. Exploration of other tire analyses
stiffness. Both the experimental data and FEA results In future studies, we plan to explore new TPMS configurations
indicate that the lattices with variable sheet thickness and incorporate auxetic behavior into the designs by modifying
outperform the uniform thickness design. The graded the implicit equations of the gyroid structure. We also
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thickness compensates for UC deformation, leading to intend to conduct further tire studies, examining commonly
variations in relative density across the structure. This studied critical key factors, such as ground interaction/rolling
grading ensures a more even radial distribution of load, resistance, 10,11,59,60 wear behavior, fatigue resistance, and
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preventing the concentration of stress in specific regions other dynamic response studies, 61,62 with a focus on how the
and improving overall performance in the variable functionally graded TPMS structure performs across various
thickness designs. In the experimental results, the 1.0 surface conditions, particularly in NPTs designed for rough
– 1.5 mm- and 1.0 – 2.0 mm-ramped designs were able terrain applications. Ground interaction and wear analysis
to withstand compression up to twice the distance, or will provide a deeper understanding of how the contact patch
more, than the uniform 1.0 mm-thick wheels. In addition, behaves under load, while fatigue and dynamic behavior
these ramped designs experienced twice or more of the studies will offer insights into the long-term durability and
load at failure compared to the uniform NPT design. The performance of the functionally graded TPMS structure
comparison between the FEA strain results and the DIC under repeated or cyclic loading conditions.
strain map displays an 8% average error, which is within
the acceptable range and falls below the 10% threshold 5. Conclusion
commonly observed in static FEA studies for NPTs. 7,8
This study explored the mechanical behavior and
4.2. Local stiffness control performance of three sub-scale TPMS-based NPT designs

The observed local stiffness variations across the TPMS with varying sheet thicknesses, fabricated using DLP AM.
designs are correlated to the distribution of material By systematically varying the thickness of the gyroid bands
sheet thickness in the TPMS gyroid design. The results within these structures, we aimed to understand how local
demonstrate that varying the thickness of TPMS tire bands and global stiffness could be controlled to enhance the
is an effective method for controlling local stiffness and performance of NPTs in extreme environments. The results
deformation in different regions of the tire. Introducing a demonstrated that increasing the sheet thickness enhances
thickness gradient reduces excessive deformation in areas the overall stiffness of the NPTs, with the 1.0 – 1.5 mm- and
like L3 (near the contact patch between the tire and the 1.0 – 2.0 mm-ramped designs exhibiting 20% and 53%
road), where greater stiffness is required. higher stiffness, respectively, compared to the uniform
thickness design. This increase in stiffness, as evidenced by
This functional gradation in TPMS gyroid structures both experimental data and FEA simulations, enabled the
strikes an ideal balance between flexibility and stiffness, ramped designs to endure greater compression and higher
making it particularly advantageous for tires in off-road loads before failure. The comparison between the FEA
and space exploration rover applications, where different strain results and the DIC strain map revealed an 8% average
regions demand customized levels of flexibility or rigidity error, which confirms the accuracy of the results. This study
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depending on terrain and operating conditions. As also highlighted the critical role of understanding the local
observed, the 1.0 – 2.0 mm tire design exhibited smoother stiffness variations across different band regions within the
deformation behavior with increased local stiffness. This ramped gyroid NPT designs. The local deformation studies
is advantageous for NPTs, as smooth deformation of the across the band regions L0 – L4 using DIC revealed that
proposed gradient TPMS-based NPT will ensure that the the 1 – 2 mm-ramped design exhibited the most uniform
load is distributed more evenly across the tire, and can hence load distribution and a reduced local deformation of 58% in
prevent localized stress concentrations or buckling, which the region near the contact patch compared to the uniform
can lead to premature structural failure in the tires. 54,55 and 1 – 1.5 mm-ramped NPTs. The proposed approach can
Advancements in AM have made it possible to print in be utilized for on-demand manufacturing of the NPTs for
space. 56,57 Combining the presented design with the AM space exploration vehicles, with tunable stiffness according
approach of thickness gradients in TPMS structures could to desired terrain conditions.
produce highly adaptable, resource-efficient, and flexible Acknowledgments
tires. This combination is particularly beneficial for space
exploration and off-road applications, where tailored The authors would like to acknowledge Ryan Overdorff, a
stiffness and flexibility are essential for navigating diverse 3D systems expert at Penn State University, for providing
and challenging terrains. advice and assistance with the fabrication process.

Volume 3 Issue 4 (2023) 10 doi: 10.36922/msam.5022