Investigation of mechanical properties of polyurethane foam filled honeycomb core sandwich composites

Honeycomb structures are generally used as core material in sandwich composites used in aircraft structures. Honeycomb structures have some disadvantages when used for structural components of aircraft. Even when polymer foam core structures are used, the cracks that occur in the core rapidly spread throughout the entire core structure. In this study, polyurethane foam – honeycomb structure combination was used as a potential material in order to eliminate the disadvantages of honeycomb core structures and polymeric foam core structures. Within the scope of the study, the honeycomb structure, which is the core material, was produced from polylactic acid filaments (PLA) using a three-dimensional printer. The produced honeycomb structure was filled with polyurethane foam and the final core structure was formed into sandwich composite form by vacuum infusion method using carbon fiber and epoxy resin, which is the facesheet material. Carbon fiber/epoxy facesheet material is produced by using vacuum infusion method in 0°/90° orientation of plain weave carbonfiber fabrics. The produced sandwich composite was subjected to edgewise compression, three-point bending, shear and moisture absorption tests. The contribution of polyurethane foam filling to the mechanical strength of the structure and its effects on moisture absorption properties were investigated.