A universal strategy for flexible, efficient and programmable crashworthiness under quasi-static and dynamic loadings based on plastic deformation of metals

Cellular materials and mechanical metamaterials respectively display desirable efficiency and programmability in engineering protection, however, the means to combine their advantages poses a challenge. To break this limit, a universal strategy based on plastic deformation of metals is established to realize flexible, efficient and programmable crashworthiness, which is implemented in three steps. Firstly, cellular material is discretized as multiple self-locked tubes, endowing it with convenient assembling and disassembling processes as well as flexible property tunability to adapt to load characteristics. Then, perforated design is executed mainly to induce efficient progressive buckling mode and superior crashworthiness by creating geometry discontinuities. Finally, nested design is employed to promote space utilization and plateau stress. More critically, multiple step functions with target characteristics can be introduced on stress–strain curve to obtain programmability by controlling parameters of fillers. The windmill-inspired system made of 316L stainless steel is taken as the instance to implement the strategy, and both quasi-static and dynamic loading conditions are considered. The strategic feasibility is validated by experiments and simulations, and specific energy absorption, energy absorption efficiency and force efficiency respectively increase by 53.8%, 13.5% and 77.9%. This research opens a new avenue for combing efficient mechanical behavior and flexible property programmability.