Temperature-independent damping is crucial in applications such as outdoor robotics, vehicles, aircraft, and spacecraft to enhance operational performance. A significant challenge in fluid dampers is the decrease in oil viscosity with increasing temperature, leading to reduced flow resistance. Active damping systems commonly use sensor-actuator systems to adjust valve openings or to trigger magnetorheological effects [1]. However, temperature-sensitive metamaterials offer a promising, material-efficient alternative to compensate viscosity changes. Metamaterials consist of structured base materials made of repeating unit cells, each exhibiting functional behaviors like damping and stiffness in response to external stimuli such as deformation and temperature [2][3]

This study investigates the use of fluid friction to regulate damping by embedding a designed metamaterial unit cell within a Couette flow system. Couette flow occurs in narrow gaps where a moving plate overlaps with a stationary plate. To counteract fluid friction reduction at elevated temperatures, two approaches are feasible: increasing the covered area or reducing the flow gap. In the developed unit cell, this is achieved through temperature-controlled rotation. Previous studies have examined shape changes due to temperature variations using materials with different coefficients of thermal expansion and shape memory polymers [4][5]. These materials were utilized to develop a mechanism for temperature-triggered rotation in this work.

For experimental validation, unit cell components were additively manufactured and assembled, followed by vertical fluid friction tests conducted across a temperature range of 20 to 80 °C. Current results clearly demonstrate the effects of variations in fixed friction gap and area coverage in the millimeter range. An analytical fluid friction model was also constructed and calibrated with the experimental data. The results indicate that the interaction between fluid and a temperature-dependent flow gap, managed by metamaterials, holds significant potential for innovative, adaptive, and temperature-independent damping solutions.

References

[1] R. Ahamed, S-B Choi, M.M. Ferdaus; Journal of Intelligent Material Syst. and Struct., 2018, 29, 2051–95.

[2] F. Wenz, I. Schmidt, A. Leichner, T. Lichti, S. Baumann, H. Andrae, C. Eberl; Adv. Mater., 2021 ,33, 2008617.

[3] W. Kaal, M.M. Becker, M. Specht, S.C.L. Fischer; Programmable Materials, 2023, 1, 1:e1.

[4] J.S. Raminhos, J.P. Borges, A. Velhinho; Smart Materials and Structures, 2019, 28, 045010.

[5] D. Schönfeld, D. Chalissery, F. Wenz, M. Specht, C. Eberl, T. Pretsch; molecules, 2021, 26, 522.