Energy absorption of a novel auxetic structure reinforced by embedding tubes

To enhance structural crashworthiness while achieving lightweight design, this paper proposes a novel configuration that embeds a thin-walled square tube into auxetic structure which can take full advantage of the interaction between the auxetic structure and embedding tubes. The finite element model of auxetic structures reinforced by embedding tubes is established and validated by the compression experiments. The crashworthiness performance of auxetic structure (AUX), auxetic structure reinforced by embedding tubes (AET), and auxetic structure-filled tubes (AFT) are compared to find that the AET have the highest energy absorption and specific energy absorption (SEA). Through parametric analysis, designing the angles between short and long beams (θ1, θ2) as 70° and 40° can contribute to the crashworthiness performance, respectively. A suitable range for long beam thickness lies between 1.4 mm and 1.6 mm, while a short beam thickness of around 1.2 mm is more effective. The specific configuration can enhance the SEA and reduces peak crushing force (PCF). Increasing the thickness of the embedded tube can improve the crashworthiness by sacrificing the weight. It is a good balance between the crashworthiness performance and weight by designing the tube thickness as 1.2 mm. An analytical model is also established to predict the energy absorption of auxetic structure reinforced by embedding tubes under axial impact loadings. The surrogate modeling technique and the NSGA-II algorithm are also employed to optimize the AET configuration. The results show that the SEA of the optimized structure can increase from 14.5 kJ/kg to 18.6 kJ/kg, while the PCF can be reduced from 164.6 kN to 124.3 kN. Therefore, the auxetic structure reinforced by embedding tubes can play a critical role in the engineering field to absorb energy.