Preliminary investigation of the large-scale sandwich decks with graded 3D printed auxetic core

This research presents an innovative sandwich bridge deck system inspired by triply periodic minimal surface (TPMS) structures for load-bearing applications. The deck features a parametrically designed graded gyroid core, optimized through structural optimization to achieve a 10% relative density. The core was manufactured using Fused Deposition Modelling (FDM) and bonded with tempered glass flanges. Numerical analysis was performed using Abaqus software with an elastic-plastic material model based on tension tests, offering a simplified yet effective approach compared to the more complex analysis possible with custom VUMAT subroutines. A single scaled prototype was produced and subjected to a three-point bending test. The results demonstrated successful bonding between the sheets and core but revealed challenges such as premature shear failure of the polymeric core, crack propagation between print beads, and compression-induced failure of the glass flanges. A size effect was identified, as tension tests were performed at a much finer resolution than the core printing, leading to a drop in the material's mechanical properties. These failure modes were correlated with numerical predictions, underscoring the need for further investigation into thermo-mechanical effects on 3D printed materials.