Experimental crushing behavior and energy absorption of angular gradient honeycomb structures under quasi-static and dynamic compression

The high variability of shock in terrorist attacks poses a threat to people's lives and properties, necessitating the development of more effective protective structures. This study focuses on the angle gradient and proposes four different configurations of concave hexagonal honeycomb structures. The structures' macroscopic deformation behavior, stress-strain relationship, and energy dissipation characteristics are evaluated through quasi-static compression and Hopkinson pressure bar impact experiments. The study reveals that, under varying strain rates, the structures deform starting from the weak layer and exhibit significant interlayer separation. Additionally, interlayer shear slip becomes more pronounced with increasing strain rate. In terms of quasi-static compression, symmetric gradient structures demonstrate superior energy absorption, particularly the symmetric negative gradient structure（SNG-SMS） with a specific energy absorption of 13.77 J/cm3. For dynamic impact, unidirectional gradient structures exhibit exceptional energy absorption, particularly the unidirectional positive gradient honeycomb structure（UPG-SML） with outstanding mechanical properties. The angle gradient design plays a crucial role in determining the structure's stability and deformation mode during impact. Fewer interlayer separations result in a more pronounced negative Poisson's ratio effect and enhance the structure's energy absorption capacity. These findings provide a foundation for the rational design and selection of seismic protection structures in different strain rate impact environments.