Wednesday  |  Allegheny  |  10:50 AM–11:10 AM

#13151, Dynamic Compressive Behavior and Deformation Mechanisms of 3D-Printed Hierarchical Re-entrant Honeycomb

Lightweight while mechanically robust structures have been widely used in automotive, defense and aerospace industries in order to satisfy the increasing demand on the impact protection. Hierarchical re-entrant honeycombs (H-ReHs) with a 2nd order triangular hierarchy, an emerging type of lightweight but robust structures have prominent energy absorption performance under quasi-static compression. The complex hierarchical structure of H-ReHs has been successfully designed and fabricated through additive manufacturing. The energy absorption capacity is determined by the unique interaction between the hierarchies, which is sensitive to the relative density of the structure. Due to the interchangeable deformation mechanisms as well as the viscoelastic nature of the printing material, it is necessary to investigate the energy performance of H-ReHs under dynamic impacts, the real loading condition in automotive crashes.
To this end, the dynamic responses of H-ReHs are characterized by a lab-customized drop tower apparatus in this work. The results show that the energy absorption capacity of H-ReHs is sensitive to the strain rates. The energy absorption capacity of the H-ReHs under dynamic impacts is an order of magnitude higher that under quasi-static loading condition. In addition, the linear pre-buckling and the nonlinear post-buckling behaviors of the H-ReHs exhibit different levels of strain rate sensitivity. This strain rate-dependent behavior is attributed to the micro-inertia effect and the localized deformation modes of the 2nd order triangular hierarchy.
These findings validate that the H-ReHs have much enhanced energy absorption capacity at higher strain rates. The dynamic behavior of the H-ReHs is determined by the structural heterogeneity of the hierarchical structure, which is a design paradigm for lightweight but robust structures.

Chi Zhan   Michigan State University
Mingzhe Li   Michigan State University
Weiyi Lu   Michigan State University