With the development of three-dimensional printing technologies, so-called cellular materials have achieved increasing attention due to outstanding properties. Unlike pure solid structures, properties of cellular materials are influenced by both utilized material and cell microtopology. The present paper proposes a novel type of re-entrant square cellular material. To explore the relationship between microtopology and macrodynamic responses systematically, an explicit dynamic finite element simulation method is used. This work starts by constructing theoretical models of relative density employing a two-dimensional unit cell. Then, the effects of geometric features and configurations on dynamic properties are explored, and simulations indicate that variations of geometric parameters strongly affect properties and that the staggered re-entrant squares are more stable than the regular re-entrant squares. Subsequently, the effects of the impact velocity on dynamic crushing behaviors are elaborated. On this basis, the relationship of unit mass energy absorption and geometric features is obtained by employing the response surface method. Furthermore, with targets of maximum unit mass energy absorption and minimum relative density, the optimal structural parameters are achieved by using non-dominated sorting genetic algorithm. The study provides a detailed introduction to dynamic behaviors of cellular materials and guidance to design new structures with superior characteristics of energy absorption.

With the ever-increasing demand in urban mobility and modern logistics sector, the vehicle population has been steadily growing over the past several decades. One natural consequence of the vehicle population growth is the increase in traffic congestion. Almost all (metropolitan) cities including the major ones, like Los Angeles, Beijing, New York, are suffering from heavy traffic congestion. Statistics show that, in 2015, 43 cities in China are suffering a prolonged travel time of more than 1.5 h every day during rush hours. In the meanwhile, traffic accidents are plaguing the economic development as well.