Tunable energy absorption of pyramid-stacked negative stiffness metastructure

Negative stiffness (NS) metastructures provide a new mechanism for energy absorption. This work proposes a pyramid-stacked negative stiffness (PNS) metastructure to achieve energy absorption tunability and improvement in micro level. The finite element method (FEM) is employed to analyze the energy absorption characteristics of PNS metastructures. The accuracy of the FE model is validated through the quasi-static loading experiment. The deformation pattern of the unit cell of PNS metastructure can be tuned from symmetric to anti-symmetric with increasing apex height, which is verified by natural vibration modes and compression experiments. The pyramid-stacked design significantly enhances the energy absorption capacity of conventional NS curved beam structures, exhibiting 14.6 % and 21.2 % improvements in energy absorption under coupled symmetric and anti-symmetric deformation patterns, respectively. Through deformation pattern and parametric analysis, multiple controlled deformation sequences are found and energy absorption is tuned in PNS metastructures with rational layouts. Finally, the strategies of stopper and gradient designs are used to tune and enhance the energy absorption efficiency and reduce the plateau force fluctuation.