Variable stiffness of metamaterial composite structure

Abstract

In recent years, numerous researchers have studied metamaterials because of their extraordinary mechanical properties that other materials do not possess. The concept of metamaterials has been widely introduced into the field of earthquake engineering. [1] This thesis presents the results of research aimed at finding a metamaterial structure with adaptive stiffness that could be used in the design of isolators and protective barriers. Such a material would reduce impact force transmission experienced by a vehicle in the event of an accident, and could also protect people in buildings during an earthquake. The goal is to develop the concept of a metamaterial that would have non-linear stiffness, and offer higher resistance against small displacements (high stiffness) but lower resistance (low stiffness) in the event of sudden impacts experienced during large dynamic excitations, While deformation in the plastic zone also results in non-linearity, the metamaterial will have the advantage of being fully elastic, and it can be used repeatedly which is environmentally friendly and reduces maintenance costs. The reversible nonlinearity is obtained by using stiffness changes associated with change in geometry. Theoretical analysis and numerical results show that it may be possible to develop such a metamaterial from cells which contain adaptive mechanisms embedded in a flexible matrix. Metamaterial can provide variable stiffness and enable significant reductions in the transmission of dynamic forces.