Dynamic failure of 3D printed negative-stiffness meta-sandwich structures under repeated impact loadings

Abstract

Achieving superior reusable energy absorption and mitigation properties under repeated impact loadings with high strain rates, yet maintaining the lightweight design feature, is still a challenge for thin-walled structure design. In this work, combined with the concept of mechanical metamaterial, several kinds of negative-stiffness meta-sandwich structures (NSMSs) are developed and their dynamic responses under repeated high strain-rate impacts are systematically investigated. The 3D printing technique of selective laser sintering (SLS) is applied to fabricate the composite NSMSs with glass fiber reinforced (GFR) Nylon. The bistability of the double curved-beam topology and the remarkable impact resistance to the repeated impact loadings are theoretically, numerically, and experimentally analyzed. An analytical model based on the Gibson-Ashby framework is presented to predict the mechanical behavior of NSMSs, and a series of evaluation indicators are developed to quantitatively describe the energy absorption performance. Compared with a conventional honeycomb structure, the unique layer-by-layer failure mode for NSMSs, leading to a significant improvement in the capacity of multiple-impact resistance, is unambiguously demonstrated. This new type of artificial structure paves a feasible way to achieve superior energy absorption and impact resistance features under repeated impacts.