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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.

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 double-V micro-structures (DVMS) are a type of auxetic materials showing the negative Poisson’s ratio which can contract under compression different from the conventional materials. Due to the unique properties, it can have higher stiffness and better impact resistance with lightweight. In this paper, a cylindrical honeycomb tube based on the double-V unit cell is proposed. Firstly, the nominal Poisson’s ration and Young’s modulus in the longitudinal and circumferential directions are derived analytically. The effect of the geometry parameters of the DVMS tube on the mechanical properties is studied thoroughly. Also, the effect of the width in the radial direction on these mechanical properties is analyzed. Secondly, the finite element (FE) method is utilized to obtain the numerical solutions and verify the accuracy of the analytical solutions. The results show that there is a good agreement between the results obtained by the two methods when the width is smaller enough.