Crashworthiness designing of a structure using a Hybrid Cellular Automata (HCA) algorithm where field states are computed using finite element analysis (FEA) and the material distribution of the structure is updated at each iteration using cellular automata method. The HCA algorithm optimizes the topology of the structures to achieve certain performance within the limits of various constraints applied to ensure crashworthiness of the structures. The HCA algorithm may also be applied to designing of structures to be fabricated by an extrusion method having the same cross section along the direction of extrusion or stamped structures having thickness varying across the structure.