Mechanical properties of auxetic circular and square tubes filled with aluminum foam

The incorporation of aluminum foam in auxetic tubes can significantly enhance the overall stability, stiffness and energy absorption properties. In this work, a comparative study of the mechanical properties between auxetic circular and square tubes was conducted. The foam-filled auxetic square tube (FFAST) has the best specific energy absorption (SEA) up to 1.45 among the four auxetic tubes, and exhibits a pronounced auxetic effect throughout the minor deformation under compression, with a symmetrical and stable deformation mode. The experimental and simulated results are in excellent agreement. Hence, the finite element method is subsequently applied to the parametric analysis of FFAST, including the effects of wall thickness, height and ellipticity. Firstly, it is found that the thinner the wall thickness of FFAST is, the weaker the peak force and the greater the specific energy absorption would be. Secondly, within the same minor strain of different heights, SEA remains almost the same. Finally, with the decrease in ellipticity, the yield load of the bore tube gradually grows and SEA progressively increases. It can be concluded that FFAST with the ellipticity of 1.69 has both a high SEA and non-peak force. These findings are useful for fabricating FFAST for individual scenarios of energy absorption requirements. Such composite tubular structures will have practical applications in, e.g., protective engineering, vehicle engineering and aerospace engineering.