Crashworthiness topology optimization of shell–infill structures

Shell–infill structures are used extensively in, e.g., aeronautic, automotive, and marine engineering. In this study, we develop a heuristic crashworthiness topology optimization method for shell–infill structures. In this method, the shell and the infill could have different mechanical properties, the material failure is taken into account, and the contributions of materials to the structural performance are assessed. In each optimization iteration, the shell is updated first, and then a new infill layout is generated. The effectiveness of our method is demonstrated through several numerical examples. Physical prototypes of the optimized designs are fabricated, and their dynamic responses are measured through drop-weight impact tests. Both the numerical and the experimental results show that our method is capable of producing shell–infill structural designs with excellent crashworthiness performance. By assigning a high-strength material to the shell in the topology optimization, the dual-material designs could have higher specific energy absorption. Two failure modes are revealed, including the sequential failure in single-material designs and the infill-prioritized failure in dual-material designs. The latter mode could reduce material failure rate and enhance mechanical robustness. In the dual-material designs, the impact-resistant properties of the optimized structures can be easily tuned by changing the proportion of shell and infill materials. This study may provide a powerful tool for designing highly efficient shell–infill structures, and help understand the impact-resistant mechanisms of natural biological materials.