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Auxetic structures/materials with the negative Poisson’s ratio (NPR) properties can contract when compressed and expand when stretched, different from the conventional structures/materials. Due to the unique properties, it can have higher stiffness and better impact resistance with lightweight. Therefore, the auxetic structures/materials have been applied in various engineering field, such as automobile crash box, suspension mount etc. For auxetic structures/materials with negative Poisson’s ratio, there are four typical configurations (re-entrant hexagonal, double-V, tetra star-shaped and tetra-chiral). However, comparisons on the dynamic behaviors and crashworthiness between the four auxetic structures have not been studied. In this paper, the finite element models were developed for four typical auxetic structures. The deformation modes and energy absorption properties of four different auxetic structures were explored under different impact velocities.

The design of aluminum foam reinforced thin-walled tubes has garnered much interest recently due to the high energy absorption capacity of these tubes. As a new kind of engineering composite material, aluminum foam can hugely increase the crashworthiness capacity without sacrificing too much weight. In this paper, axisymmetric thin-walled hollow tubes with four different kinds of cross-sections (circular, square, hexagonal and octagonal) are studied to assess their performance for crashworthiness problems. It is found that the tube with square cross-section has the best crashworthiness performance under axial impact. To seek optimal designs of square aluminum foam reinforced thin-walled tubes, a surrogate modeling technique coupled with a multi-criteria particle swarm optimization algorithm has been developed, to maximize specific energy absorption (SEA) and minimize peak crash force (PCF).

Thin-walled tubes have been mostly used in passive vehicle safety systems due to high crash energy absorption. The structures with negative Poisson’s ratio (NPR) property will contract to increase its stiffness. In this paper, a double-arrowed NPR structure is designed as a new energy-absorption filler for thin-walled tubes to apply as a novel crash energy absorber. Different beam thicknesses, angles and half cellular width are taken into account in the double-arrowed NPR filling tubes (DAFT) designing and the crashworthiness of the structures are analyzed by using validated nonlinear finite element method. The crashworthiness performances of DAFT are also compared with the singular NPR and hollow tube with the same outer dimension to show the efficiency of DAFT.