Crashworthiness of graded cellular materials: A design strategy based on a nonlinear plastic shock model

Dynamic behaviors and crashworthiness design of density graded cellular materials are investigated by using theoretical method and finite element simulation. A nonlinear plastic shock model is employed to guide the gradient design of cellular rod under mass impact and cell-based finite element models are used to verify the design strategy. Effects of impact-force parameter on the design of relative density distribution of graded cellular material and on the residual velocity of the striker for different lengths of graded cellular rods are explored. Three cases of design strategy with different impact-force parameters are analyzed and verified. The results reveal that the design strategy is reliable when the impact-force parameter is not less than zero. If the relative density distribution of graded cellular rod increases monotonically, the actual deformation mode of graded cellular rod is identical with the assumed one in the theoretical derivations. It is noticed that a portion of the graded cellular rods close to the distal end is not fully compacted. A scheme with restricting the shock strain not less than a specific value is proposed to shorten the graded cellular rods. Therefore, the desirable crashworthiness of graded cellular materials can be obtained by designing the density distribution of graded cellular materials.