Modelling and bending analysis of a 3D-printed sandwich structure with an auxetic star-4 core

Abstract

Quasi-static 3-point bending of additive manufactured sandwich components with auxetic star-4 cores was investigated to obtain information on the influence of geometry parameters of the auxetic structure on the stress distribution of the face sheets. Experiments were carried out on specimens manufactured by fused deposition modelling from a PLA polymer to verify a simulation model for analyses. A hyperelastic material model was used in the finite element models to describe the elastic material behaviour and a hardening model to consider plasticity. Nanoindentation tests on the printed structures were conducted to identify the material parameters with modelling the nanoindentation procedure using the finite element method and applying automated optimisation techniques. This approach enabled an accurate reproduction of the nanoindentation tests in the simulations. The derived models for analysing the auxetic geometry have shown that the stress distribution in the face sheets of the sandwich components can be noticeably influenced with targeted changing the wall thicknesses of the auxetic star-4 structure. The simulations have also made it apparent that more effort is required to take into account the influences of the printing process on the deformation behaviour of the sandwich structure in the simulation model.