In-Plane Compressive Responses of Non-Homogenous Re-Entrant Honeycombs Fabricated by Fused Deposition Modelling.

Auxetic structures, with re-entrant (inverted hexagonal or bow tie) unit cells, have received considerable interest due to their negative Poisson's ratio property that results in superior mechanical properties. This study proposes a simple method to create non-homogeneous re-entrant honeycombs by modifying the size of chevron crosslinks. The various structural designs were conceived by changing the geometrical dimensions of the crosslinks, namely the length (lcl) and the thickness (tcl), while maintaining the parameters of the re-entrant cell walls. The influence of the design parameters of chevron crosslinks on the mechanical behaviour of additively manufactured re-entrant honeycombs was investigated experimentally and numerically. The structures were fabricated using the Fused Deposition Modelling (FDM) technique from polylactic acid (PLA) plastic. In-plane quasi-static compression tests were conducted to extract the elastic, plastic, and densification properties of the structures. Furthermore, a Finite Element (FE) model was developed via LS-DYNA R11.0 software, validated experimentally, and was then used to obtain a deeper insight into the deformation behaviour and auxetic performance of various designs. The obtained results revealed that the mechanical performance of re-entrant honeycombs can only be tuned by controlling the geometrical configuration of chevron crosslinks.