Exploring bending behavior of curved sandwich panels with three-dimensional printed, functionally graded cores

Sandwich structures have garnered significant attention due to their high strength-to-weight ratio in various industries, particularly aerospace. Meeting application demands requires optimizing mechanical properties such as bending stiffness, peak load, specific absorbed energy, and weight. This study presents a unique approach involving the design and manufacturing techniques of curved sandwich panels with functionally graded cores, aiming to achieve a comprehensive spectrum of bending properties. Curved structures have applications across diverse fields, including landing gear. The semi-circular core of the sandwich panel comprised three distinct regions defined by angles: Ф, Υ, and 90-Ф- Υ. These angles specified both the location and proportion of different honeycomb cells, including high, medium, and low-density cells. Any variations in these angles and their cell types resulted in a new density gradient. The manufactured sandwich structures consisted of polylactic acid cores printed by a fused deposition modeling printer, sandwiched between aluminum skins. Experimental tests and finite element analysis for three models showed strong agreement, with a maximum error of 14.45%. After the simulation was validated, it expanded to cover other configurations. Subsequently, mathematical models based on the aforementioned angles were calibrated using results extracted from the simulation step. This process led to achieving various structures characterized by a wide range of stiffness (ranging from 0.29 to 0.79 kN/mm), peak load (ranging from 1.73 to 4.77 kN), and specific absorbed energy values (ranging from 41.78 to 96.09 J/kg). The proposed methodology exhibits promise in engineering the design of these structures and their multi-objective optimization.