Development of a Frictional Mechanical Metamaterial for Repeatable Energy Dissipation

Abstract

Frictional mechanical metamaterials are a class of metamaterials engineered to dissipate energy through internal friction when subjected to external forces. Unlike conventional metamaterials that rely on plastic deformation or viscoelastic materials for energy absorption, frictional mechanical metamaterials can exhibit viscoelastic-like behaviour even when composed of purely elastic materials. This unique property is governed by the internal structure of the unit cell and the contact surface topography, which influence the frictional interactions within the metamaterial. Despite their potential for applications in energy dissipation and impact mitigation, the optimal architectures and scaling laws governing their performance remain underdeveloped. Similarly, the role of frictional metasurfaces—planar structures that leverage artificial surface designs to enhance frictional interactions—has not been systematically explored in the context of energy dissipation.

This research addresses these gaps by developing novel frictional mechanical metamaterials and metasurfaces designed to maximise repeatable energy dissipation per unit volume. A comprehensive approach combining finite element (FE) simulations, theoretical modelling, and experimental validation was employed to investigate the mechanical behaviour of these metamaterials. Through iterative design and analysis, a pinwheel-based internal structure was introduced to optimise the contact area and enhance energy dissipation while maintaining a compact unit cell volume. Additionally, metasurface designs incorporating right-angled isosceles triangles, rectangles, and semi-elliptical patterns were explored to assess their impact on peak force and energy dissipation efficiency.

Experimental validation was conducted using materials with both linear and nonlinear mechanical properties. For TPU 95A, a hyperelastic and viscoelastic polymer, a refined simulation approach was developed to capture its complex mechanical response. Theoretical models were modified to incorporate internal damping elements, ensuring better alignment with experimental results. These studies demonstrated that strategic modifications to internal structure geometry, contact surface topography, and material selection could significantly enhance energy dissipation performance.

The findings of this research contribute to the fundamental understanding of frictional metamaterials and metasurfaces, offering new design principles for optimising their mechanical performance. The proposed architectures have broad applicability in various industries, including high-performance braking systems, aerospace vibration damping, protective gear such as reusable helmets, and earthquake-resistant structural elements. By bridging the gap between theoretical design, numerical modelling, and experimental validation, this study lays the groundwork for future advancements in frictional mechanical metamaterials and their real-world implementation.