Active metamaterials: unit cells for tunable damping

The concept of metamaterials has been extended from electromagnetics and acoustics to the field of mechanics. Metamaterials do not derive their properties from those of the composite, but from the artificial meso-scale geometry as well as from the unit cell structure. Mechanical metamaterials are constrained in that the mechanical properties are precisely defined and fixed; alteration between these properties simply is not feasible. However, if activated, metamaterials can be controlled and mechanical properties can be influenced. In this research project, a novel active metamaterial unit cell design for controlled damping has been introduced. Centimeter-scale electromagnetic actuators are integrated as activators in an elastic mechanical metamaterial structure. The design effectively exploits the way in which the reluctance actuator functions, and tuning of the integrated electromagnet allows for ranging Coulomb damping. A proof-of-principle unit cell demonstrator of 90mm and one of 45mm, in length have been made. The electrically controlled damping behaviour of the active unit cells has been validated for cyclic loading deformations and the force-displacement curve has resulted in a damped over stored energy range from 3% and 20% up to 34% and 132% respectively