Crushing analysis and crashworthiness optimization design of reinforced regular hexagon honeycomb sandwich panel

Honeycomb sandwich panels (HSP) have exhibited significant advantages in light weight and energy absorption, and they have been widely applied in the automotive, aerospace, transportation and defense industries. Rather than restating details of the existing standard regular hexagon HSP (R0-HSP), this paper introduces single-rib reinforced regular hexagon HSP (R1-HSP) and double-rib reinforced regular hexagon HSP (R2-HSP). The mechanical characteristics of these three structures are first investigated by series full-scale elaborator models through LS-DYNA. It is found that the R1-HSP has the best crashworthiness performance under axial impact regarding specific energy absorption per unit (SEAm and SEAv) when the peak crashing stress (σpeak) is less important. Secondly, the thickness matching effect between stiffener and cell wall is analyzed with equivalent apparent density index to evaluate the contribution of the change of deformation model to the general mechanical properties. Consequently, stiffener thickness of 2.0 times and 1.5 times that of cell wall are found to be the most optimal options for R1-HSP and R2-HSP, respectively. To optimize the crashworthiness of the R1-HSP, optimal Latin hypercube design method is used for selection of sampling design points in the design space. And in the meantime, an accurate surrogate modeling method, or more specifically named as response surface method, is adopted to formulate the SEAm, SEAv and σpeak functions. The results yielded from the optimization indicate that the R1-HSP is superior to R0-HSP both in SEAm and SEAv under the same limitation of σpeak. This research is significant in providing technical support in the extended applications of different HSPs used as crashworthiness structures, and it has essential reference value in low volume and low mass energy absorber design