Investigation of mechanical properties of cellular sandwich structures produced by additive manufacturing

Additive manufacturing methods provide prototypes and final products without the need for mold design and costs. Complex geometries can be produced with high dimensional precision with additive manufacturing methods. On the other hand, cellular hollow sandwich structures are preferred in engineering applications due to their high specific strength. The shape of the cellular spaces and the size of each detail directly affect the final product properties. At this point, the flexibility, high precision and single-step product availability of additive manufacturing methods in production come to the fore. Cellular hollow structures with different geometries created with solid design software can be produced with an impressive combination of 3D printing and production precision in one go. In this thesis study, a sandwich structure with hexagonal cell, cylindrical cell and euxetic cell geometry was designed. Cell wall thickness and cell height were changed in the designs, provided that the total sandwich height remained constant. These cell designs were used and samples were produced using the Stereolithography (SLA) additive manufacturing method. Tensile, three-point bending and compression tests were carried out with the produced samples and strength values were found. Specific strength values were compared by dividing the results by the sample weight. Regardless of the cell geometry, the specific tensile strength of the sandwich structure decreases as the cell height increases. At the same time, samples with low wall thickness have higher specific tensile strength. Sandwich structures with hexagonal and cylindrical geometry showed the highest specific bending strength. Higher specific bending strength was observed in samples with higher wall thickness. As the cell height increased, bending strength values increased. In sandwich structures with hexagonal and cylindrical cells, the highest compressive strength was observed in samples with low wall thickness, while in euxetic cell structures, higher compressive strength was observed in samples with high wall thickness. As the cell height increases, compressive strength values decrease in all cell geometries.