Flexural response of additively manufactured honeycomb sandwich structures with continuous density-gradient variations.

• Honeycomb sandwich structures with continuous density gradients are designed. • Flexural behavior is sensitive to horizontal but insensitive to vertical gradients. • Achieved favorable flexural resistance with horizontal arched density distribution. • Detrimental effects from thin cover plates and honeycomb layers are indicated. Sandwich structures with graded cellular cores exhibit promising flexural performances, but their reliance on gradient continuity and distribution warrants further exploration. In this study, seven honeycomb sandwich structures with diverse continuous density gradients, encompassing horizontal, uniform and vertical variations, were designed based on the Voronoi technique and fabricated via 3D printing. Quasi-static three-point bending tests and numerical simulations were conducted to comprehensively analyze the flexural response of density-graded honeycomb sandwich structures. The results reveal a significant influence of the honeycomb core's density distribution on flexural performance, with pronounced sensitivity to horizontal distribution (perpendicular to the loading direction) and less sensitivity to vertical distribution. A favorable flexural resistance is achieved by strategically assigning higher relative density cells to the mid-span of a honeycomb core layer, gradually diminishing towards the ends, which was further optimized into an arched density distribution along the horizontal direction. The influences of cover plate and honeycomb thicknesses on the deformation mechanisms and energy absorption were also investigated, and indicate that thin cover plates and honeycomb layer have a detrimental effect on the bending load-bearing and energy absorption of the sandwich structure. [ABSTRACT FROM AUTHOR]