Investigation into the shape memory behavior of peanut-pattern auxetic structures

Abstract

In the last decade, auxetic structures with a negative Poisson’s ratio have attracted the attention of experts in industries such as biomechanics, aerospace, and packaging due to their properties, such as energy absorption and high crack resistance. The preparation of these structures using smart polymers increases their attractiveness due to low energy expenditure at the destination and the deformation of two separate states by applying external stimuli. This study aimed to investigate the improved peanut-shaped structure that retains its auxetic properties at high elongation, the effects of changes in geometry and dimensions of the structure on the Poisson’s behavior, shape fixity ratio, and shape recovery ratio during the shape memory cycle. To this end, several samples were prepared using the 4D printing method of shape memory polymers, and laboratory results were compared with software simulations of the shape memory cycle. After validating the simulation results, more cases were examined by the modeling. The results showed that despite the complete recovery of samples, the Poisson’s ratio was not recovered. The changes in geometry and samples’ dimensions significantly enhanced their auxetic property. Due to obtaining a significantly high Poisson’s ratio by changing the geometric characteristics, this structure is suggested to be used in industrial applications such as aerospace.

Keywords

• smart polymers
• 4d printing
• auxetic structures
• peanut
• modeling and simulation