Cost and Weight Optimization of Recyclable Honeycomb Sandwich Panels

In this study, four-parameter sub-optimization considering their failure modes has been performed on honeycomb core sandwich panels to obtain optimal weight. Five common failure criteria were used in the analysis of sandwich beam under four-point bending (quarter-span), considering the core material to be isotropic or specially orthotropic. The five chosen failure criteria yielded five different failure mode combinations. The sub-optimal weights for the five failure mode combinations were obtained at the confluence of four failure criteria, of which one is the global optimum. Aluminum (5052-H34 alloy) was chosen as the facesheet material with the core material types (unreinforced and fiber reinforced composites). The shear strength of all fiber-reinforced cell wall materials has been assumed to be 0.6 times the tensile strength of the material in the direction of the fibers, and the fiber volume fraction, v_f was taken to be 0.3 for all fiber-reinforced core materials. The optimal weight index was determined for load indices ranging from 1 × 10⁻⁸ to 1 × 10⁻⁶, which corresponds to loads (per unit width) between 703 N/m and 70300 N/m. On close examination, the dominant mode of failure for these panels at lower relative densities closer to 10⁻⁴ is intracellular bucking, which changes to core buckling when the relative densities get closer to 10⁻³, but at higher relative densities, this changes to facings cracking in tension. The optimal weight index predicted by the manual and Matlab procedure was 0.42 kg/m³ at a failure combination of FC-FW-IB-CB. However, the Matlab optimization predicts the same weight index at the confluence of only three (FW, IB, and CB) failure criteria, as opposed to the confluence of four failure criteria (FC, FW, IB, and CB) in the manual optimization method.