Reduced-order modeling and optimization of sandwich pipe beams with graded corrugated cores based on the mechanics of structure genome

Solar-powered unmanned aerial vehicles (UAVs) are prone to excessive flexibility and structural instability because of their ultralightweight design. The NASA Helios aircraft incident exemplifies this risk, as structural flexibility was a major contributing factor to the pitch oscillations that led to structural breakup. Improving the stiffness-to-weight ratio of the tubular structures—the primary load-bearing members—is thus essential for improving aircraft performance. For this purpose, in this paper, sandwich pipe beams with longitudinal trapezoidal corrugated cores—either uniform or graded—were proposed, and their bending capacity was investigated. To overcome the computational complexity of such structures and enable iterative optimization, we extend the mechanics of structure genome (MSG), which, through its explicit and reversible macro–micro strain mapping, is further advanced to predict not only stiffness but also failure loads, thereby serving as the foundation of the model reduction framework. Case studies revealed that the framework reduces degrees of freedom to <5 % of those of the full finite element models while retaining high accuracy, with discrepancies of 2–6 % for stiffness and failure loads and 14.1 % for local buckling loads, enabling efficient evaluation and optimization of the proposed structures. An experimental study also validated the method's accuracy. Combined with Bayesian optimization, sandwich pipe beams with graded and uniform corrugated cores were optimized and compared with those with common isotropic cores. The optimization results revealed that the optimal beam with a corrugated core achieved 31.0 % and 32.3 % increases in bending stiffness and failure load, respectively, compared with those with a polymethacrylimide (PMI) core, whereas the weightiness of the graded core further decreased by 10.6 %, offering new insights for load-bearing structure design for solar-powered UAVs.