Numerical characterisation of auxetic behaviour and flexural response in novel hybrid bio-inspired sandwich panel

This paper presents a comprehensive flexural and modal analysis of a novel nature-inspired auxetic sandwich plate using a finite element (FE) framework within the ANSYS ® platform. The sandwich structure features a hybrid auxetic core, combining a turtle-inspired cellular configuration with an integrated conventional re-entrant architecture and is attached to carbon fibre-reinforced polymer (CFRP) face sheets on both the top and bottom surfaces. The effective elastic properties of the core are calculated through a full-field homogenisation approach using the material designer tool in ANSYS, and these effective properties are utilised further for the flexural and modal response (free vibration) of the sandwich panel in ANSYS mechanical. The study explores the effect of key design constraints or parameters on the deformation behaviour of the structure, highlighting the effects of various configurations on its mechanical performance. First, to check the robustness of the present method, the RVE-assisted FE methodology has been validated against benchmark results from existing literature. Subsequently, a detailed flexural and modal analysis is carried out on the sandwich structures, both with and without an enclosing re-entrant structure within the turtle-inspired core unit cell. Two specific configurations are considered: (i) A turtle-inspired sandwich structure (TISS), and (ii) A turtle-inspired hybrid sandwich structure (TIHSS). Results indicate a noticeable increase in the overall stiffness of TIHSS when the re-entrant structure is enclosed within the turtle-inspired core, while TISS exhibits a higher natural frequency due to lower mass density. Several additional numerical examples are provided to explain the effects of varying influential design parameters, demonstrating the potential of this hybrid auxetic structure to improve the mechanical performance of sandwich plates.