Mechanical response of a novel hybrid tube composed of an auxetic outer layer

In this study, the deformation and energy absorption characteristics of a novel hybrid tube is investigated both experimentally and numerically. The architecture of the proposed hybrid tube composed of an inner conventional tube and a co-axially arranged outer auxetic tube. Quasi-static compressive tests were conducted on the auxetic tubes, the conventional tubes and the hybrid tubes. A three-dimensional digital image correlation technique was used to monitor the evolution of radial contraction of the tubes. Measured performance of the tubes were compared in terms of force, energy absorption, and specific energy absorption. Finite element (FE) models were also developed for the three types of tubes, analyzed using ANSYS/LS-DYNA, and validated by experimental measurements. Both experimental and numerical results showed that the presence of the auxetic tube in the hybrid tube alters the deformation mode of the conventional tube by exerting a radial force. Parametric studies were performed to investigate the effects of the outer auxetic tube, wall thickness of the inner conventional tube, the failure strain, and yield strength of the outer tube's material on mechanical performance of the hybrid tube. Increasing the yield strength of the outer auxetic tube improved both the energy absorption and specific energy absorption characteristics of the hybrid tube significantly.