Mechanical shock reduction mechanisms of locally resonant lattice metamaterials

Abstract

A novel locally resonant lattice metamaterial (LRLM) has been designed to meet multi-functional requirements by resolving the contradiction between high load-bearing capacity and efficient shock reduction, while ensuring reusability. This work presents the first investigation into the propagation mechanism of aperiodic oscillating (mechanical) shock loads in the LRLM, which fundamentally differs from the behavior observed under harmonic loads or transient blast/impact loads. The designed LRLM is composed of equivalent body-centered cubic (EBCC) lattices with high strength and local resonators generating tailoring band gap. The maximum relative difference in the pseudo velocity shock response spectra (PVSRS) corresponding to the LRLM and the lattice metamaterial (LM) without local resonators reaches 7.87 dB by the drop-weight test. The frequency range (<767, 1024> Hz) of the maximum shock reduction obtained by the drop-weight test is slightly smaller than that (<820, 1244> Hz) of the theoretical band gap (or negative mass density) obtained by its idealized dynamic model, and their error is attributed to the loose installations of local resonators. Furthermore, the propagation and attenuation of the shock-waveform (SW, which can be used to characterize any shock loads) with intense waveform effect in the LRLM are also investigated. The results indicate that shock reduction effects of the LRLM against SWs with larger waveform coefficients (WCs) are more remarkable than that against both harmonic waves and SWs with smaller WCs. The proposed SW shock reduction method underpins that LRLMs with vibration reduction effect can also be used to reduce shock loads as the protective structure in severe shock engineering fields.