Crashworthiness of a hybrid tube with an auxetic layer

Hybrid tubes of different forms have been designed and used in various sectors such as automotive, medical, pipeline, and aerospace industries for protective equipment, oesophageal stents, oil and gas pipes, and superior vibration dampers. Auxetic materials and structures have received increasing attention due to their unique properties such as negative Poisson's ratio. They laterally expand under uniaxial tension or laterally contract under uniaxial compression. In this work, an innovative hybrid tube with an auxetic tube as the outer tube and a conventional tube as the inner tube has been investigated. All the inner tubes were made of extruded aluminum alloy 6063 with T5 heat treatment, and the outer tubes were made of stainless steel 304 and 316L with oval holes, respectively. Quasi-static compressive tests have been conducted to study the crashworthiness of such hybrid tubes. The effects of outer tube material and geometry on the deformation mode, force–displacement curve and energy absorption of hybrid tubes have been discussed. The results show that the outer auxetic tube changes the deformation of the inner tube. The load carry capacity and energy absorption of a hybrid tube increase with the strength of the outer auxetic tube.