Mechanical Metamaterials and Their Engineering Applications

Abstract

In the past decade, mechanical metamaterials have garnered increasing attention owing to its novel design principles which combine the concept of hierarchical architecture with material size effects at micro/nanoscale. This strategy is demonstrated to exhibit superior mechanical performance that allows us to colonize unexplored regions in the material property space, including ultrahigh strength-to-density ratios, extraordinary resilience, and energy absorption capabilities with brittle constituents. In the recent years, metamaterials with unprecedented mechanical behaviors such as negative Poisson's ratio, twisting under uniaxial forces, and negative thermal expansion are also realized. This paves a new pathway for a wide variety of multifunctional applications, for example, in energy storage, biomedical, acoustics, photonics, and thermal management. Herein, the fundamental scientific theories behind this class of novel metamaterials, along with their fabrication techniques and potential engineering applications beyond mechanics are reviewed. Explored examples include the recent progresses for both mechanical and functional applications. Finally, the current challenges and future developments in this emerging field is discussed as well.

On the Investigation of Surface Integrity of Ti6Al4V ELI Using Si-Mixed Electric Discharge Machining

“…Titanium and its alloys are being used in automotive, aeronautical, biomedical and a number of other industries due to their exceptional properties. Titanium alloy Ti6Al4V ELI (grade 23) is solely developed by in view of biomedical industry applications [1,2]. It contains low levels of interstitials that have improved mechanical and thermal properties than grade 5.…”

Electromagnetism, axions, and topology: A first-order operator approach to constitutive responses provides greater freedom

“…Since the axionic response is outside the scope of standard electromagnetism, we will utilise concepts from the area of mechanical metamaterials [38,39], albeit ones driven by applied electromagnetic fields, and which -with the addition of moving charged elements, can generate currents. It is the mechanical movement and couplings of the metamaterial component that create constitutive properties of the necessary orientation for an axionic response.…”

Healable, memorizable, and transformable lattice structures made of stiff polymers

“…Precisely, architected lattice structures with extraordinary properties, including low density, high specific stiffness, high specific strength, and high energy absorption, have been used in a broad range of engineering applications such as aerospace panels, impact absorbers, acoustic modulators, thermal exchangers, battery electrodes, and biomedical scaffolds [1][2][3][4][5][6][7][8][9] . A key limitation in most existing lattice structures is that their properties and functions may not be modulated once fabricated.…”

“…Equipped with coupled features, including additive manufacturing, fracture healing, and shape memory, our lattice structures may open promising avenues for smart lightweight structures that can reversibly transform architectures and recover damage through fracturememory-healing cycles. These healable, memorizable, and transformable lattice structures may find broad applications in next-generation aircraft panels, automobile frames, body armor, impact mitigators, vibration dampers, and acoustic modulators [1][2][3][4][5][6][7][8][9] .…”