The effects of non-uniform infill patterns on compression behaviour of semi-auxetic structures manufactured using FDM: Experimental and numerical approaches

Mechanical cellular metamaterials offer significant potential for tailoring mechanical performance through geometric design. Previous studies have investigated hybrid hexagonal and re-entrant honeycomb cellular architectures, the influence of non-uniform infill distribution within these auxetic lattices is the goal of this research. This study proposes three hybrid auxetic lattice configurations incorporating different non-uniform infill distributions. Samples are designed, fabricated using fused deposition modelling (FDM), and evaluated under quasi-static compressive loading. Experimental compression tests were performed and compared with finite element simulations to investigate the initial mechanical response of the proposed structures. The validated numerical model was subsequently employed to conduct a parametric investigation of selected geometric parameters, including unit-cell thickness, scaling factor, strut angle, and connecting-strut length. To assess the deformation behaviour, initial strain energy capacity, and specific initial strain energy capacity of the structures, finite element analysis was employed and verified via experimental testing. The findings indicate that the structure with an increased infill pattern towards the top and bottom parts exhibits the highest specific initial energy absorption by up to 20%, and the structure with central accumulation demonstrated the highest load-carrying capacity. Regarding the mechanical compliance, the structure with increased infill in the middle section was proven to be the most effective. The results further indicate that non-uniform infill distribution affects both structural compliance and energy absorption efficiency by altering load transfer pathways and deformation localization within the lattice. The findings provide preliminary insight into the role of spatial infill distribution in hybrid auxetic- honeycombs.