A numerical study on the in-plane dynamic crushing of self-similar hierarchical honeycombs

摘要

Rather than restating the quasi-static mechanical characteristics of hierarchical honeycombs, this paper aims to explore the coupling effect between self-similar hierarchical characteristics and dynamic mechanical properties. Systematic simulations of hierarchical honeycombs subject to in-plane impact loading indicate that the introduction of a self-similar hierarchy does indeed enrich the types of local deformation bands. Appropriately increasing the hierarchical structural parameter of the honeycomb has the same effect as increasing the impact velocity, which leads to the formation of a localized "I"-shaped deformation band, and hence improves the energy absorption capability. However, deformation patterns can also be categorized into quasi-static, transition, and dynamic modes. The critical velocities at which deformation patterns transit can be obtained from the classification map. By using this method, it is possible to analyze the stress-strain curves of hierarchical honeycombs at the impact end and the plateau stresses in association with the deformation profiles. The following analysis of relative plateau stress further demonstrates that self-similar hierarchical characteristics are favorable for improving the overall performance of honeycombs. When the impact velocity is uncertain, the hierarchical honeycomb has superior energy absorption capability when the hierarchical structural parameter ranges from 0.3 to 0.4. Through the observation and analysis of the results from many cases, it is proven that the hierarchical structural parameter and the impact velocity affect the densification strain simultaneously. The empirical equations of dynamic densification strains for hierarchical honeycombs under different deformation patterns are derived by using least-square fitting.