Experimental and theoretical investigation of the influence of core density on the stiffness of lightweight honeycomb sandwich panels

Due to their exceptional mechanical properties and multifunctionality, sandwich panels are now used in a wide range of applications, including aircraft, ships, and wind energy systems. In this study, the effect of core density value on sandwich structure performance was studied by utilising several available theoretical solutions for regular hexagonal honeycomb core types as commonly used in aircraft structures, based on its high strength-to-weight and stiffness-to-weight ratios. The theoretical solutions utilised in this study all involved determining the total deflection of such sandwiches when these are subjected to bending stresses and thus determining the relationship of core density to such deflection values. These theoretical values were then used to conduct a practical investigation into the effect of core density on deflection and, consequently, stiffness. Samples with varying densities were prepared by adjusting the relevant cell size value to three magnitudes (9.5 mm, 7.52 mm, and 6.2 mm) and utilising 3D printing technology to create models from polylactic acid (PLA) material. The samples were then subjected to the loading conditions outlined in the standard ASTM C393-00 requirements using a three-point bending test to investigate sandwich panel deflection and stiffness and agreement with the theoretical results. Determining how the experimental test results followed the theoretical results thus produced a clearer understanding of how increasing the core density can make sandwich panels stiffer and reduce their flexural deflection.