Influences of skin thickness, core topology, depth and direction on flexural deformation and ductile failure of Al honeycomb-based sandwich structures

To systematically explore the effects of skin thickness, core topology, core depth and core direction on crushing deformation, failure behavior, mode and mechanism of aluminum (Al) honeycomb-based sandwich structures, a series of sandwich panels with various honeycomb core structures and skin thicknesses are prepared and deformed in the out-of-plane three-point bending deformations. Particularly, auxetic and non-auxetic honeycomb structures with an ultrathin cell wall thickness are investigated. Finite element simulations of all flexural deformations are conducted with the mixed Swift-Voce constitutive model which accurately describes plastic deformation. The numerical model is well validated by comparisons of the experimental load-deflection responses and simulation results. Ductile failure modes in Types I, II and III are identified, and their behaviors and mechanisms are numerically reproduced. Although core topology has a negligible effect on the failure mode, skin thickness, core depth, and core direction do. Additionally, using an auxetic honeycomb core, such as a reentrant unit, improves peak load, energy absorption, and the corresponding specific values of honeycomb-based sandwich structures. Increases in core depth and skin thickness, on the other hand, do not result in a consistent increase in specific peak load. To achieve a lighter and stronger Al honeycomb-based sandwich structure, utilizing a reentrant honeycomb core rather than a traditional non-auxetic core is more effective than increasing core depth and skin thickness. © 2022 Elsevier Ltd