Research on the cushioning and energy absorption characteristics of gradient sinusoidal negative Poisson’s ratio honeycomb structures

In this study, we designed improved cellular materials (CMs) with good energy absorption capacities, proposing new types of CMs with negative Poisson ratios by introducing sinusoidal cell walls and three different gradients. The amplitude of the sinusoidal wall, cell periodicity, and cell wall thickness were modulated in three layers across the structure (denoted as AG-CM, PG-CM, and WTG-CM, respectively). The influence of the different gradient parameters on the dynamic response of the CMs was analysed. The finite element method was used to explicitly simulate the deformation behaviour, dynamic shock stress, and energy absorption characteristics of the proposed structures at different impact speeds and directions. The initial peak stress in the face of the impact of the CM with a reasonable gradient setting was lower than that of the non-gradient CM. In contrast, its energy absorption was higher than that of the non-gradient CM. WTG-CM exhibited the highest energy absorption for a low-speed impact (7 m/s). For a medium and high speed impacts (35 m/s and 70 m/s), AG-CM exhibited the highest energy absorption in the face of positive gradient impact, whereas WTG-CM exhibited the highest energy-absorbing energy when impacting against the gradient. Under similar impact rates, the energy absorption energy of the different CMs varied by 32.1%. For the same CM, the maximum difference in absorption energy between shock modes was 33.8%.