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Bionic and gradient designs offer promising applications in honeycomb structures. The intersection unit of the beetle elytra is extracted as to enhance regular hexagonal honeycomb (RHH), and several bionic honeycombs are proposed. Finite element (FE) modeling approach is verified through formulae and experiments. Curves of force and displacement of bionic honeycombs present two prominent stages under medium- and low-speed impacts in plateau stage, and several bionic honeycombs exhibit a zero or negative Poisson's ratio. The specific energy absorption (SEA) of INT_6, whose crashworthiness is best in bionic honeycombs. A gradient design of INT_6 is implemented to further increase its crashworthiness. Multi-objective optimization design (MOD), which aims to simultaneously increase the SEA and reduce the peak crushing force, is adopted to determine the optimal parameters of each layer of graded INT_6. The SEA of the optimized graded INT_6 increase 142%, and its peak crushing force decrease by 25.4% compared with those of the INT_6. [ABSTRACT FROM AUTHOR]

• Inspired by beetle elytra intersection unit, a series of novel bionic honeycombs were designed. • Several bio-honeycombs exhibit zero or negative Poisson's ratio. • Bio-honeycombs can improve plateau stress and reduce the peak force effectively. A series of novel bionic honeycombs (bio-honeycombs) are proposed by incorporating the microstructure of the beetle elytra intersection unit into the regular hexagonal honeycomb (Hex) cell. To explore the in-plane mechanical properties and energy absorption performance of bio-honeycombs under different impact speeds, finite element (FE) models are established and verified by empirical formulas and current experiments. The results indicate that the bio-honeycombs outperform the Hex in terms of energy absorption capacity, and the nominal stress–strain curves of the bio-honeycombs show two prominent stages (stage Ⅰ and stage Ⅱ) under quasi-static and mid-impact. Bionic units also undergo two evident deformation stages: preliminary collapse and further crushing. The bending and traction of bionic units make more adjacent cells added to the collapse earlier, forming a global crushed trend, leading to an interesting phenomenon that the localized band of bio-honeycombs are always wider than that of Hex. Also, negative Poisson's ratio is observed in stage Ⅱ from several bio-honeycombs under quasi-static and mid-speed due to bionic units' bending and traction in the further crushing stage. Besides, the number and distribution of ribs have a considerable impact on the crashworthiness of bio-honeycombs. Compared with the Hex, the incorporated bionic units reduce the peak crushing force (PCF) while improving the crashworthiness of bio-honeycomb in the case of the same relative density, which provides a promising potential solution to strengthen the energy absorption performance of honeycomb structures. [ABSTRACT FROM AUTHOR]

In order to improve the crashworthiness of the crash box, the cattle horn is selected as a bionic object. A crash box filled with negative Poisson's ratio honeycomb based on horn structure was designed by extracting its excellent structural characteristics of impact resistance. The axial deformation modes and energy absorption characteristics of bionic crash box are investigated by means of finite element method, and compared with square crash box, diagonal crash box and side-to-side crash box. Under axial impact, the horn-bionic crash box shows significantly better load-carrying and energy-absorbing capacity than the square crash box and the diagonal crash box. On this basis, the thickness parameters, multi-objective optimization design and structure improvement design of horn-bionic crash box are studied successively in this work. The results show that the improved bionic crash box based on horn structure has a typical progressive shrinkage deformation mode. Its SEA reaches 29.9 kJ/kg, which is 2.5 times that of the square crash box, and its PCF is also greatly reduced from 542.4 kN to 391.1 kN. Therefore, the methods of structural improvement such as pre-deformed treatment, constraint beam adjustment and shortening the NPR core can effectively reduce the PCF of the crash box, and improve its energy absorption capacity, so as to obtain better comprehensive crashworthiness. Introducing the key characteristics of the horn structure into the design of the car crash box can effectively improve structural crashworthiness and provide new design guidance for the other energy-absorption components of vehicle. [ABSTRACT FROM AUTHOR]