Fabrication and Compression Properties of Two-Layered Porous Structure of Different Materials by Direct Printing of Resin Porous Structure on Aluminum Foam Using a 3D Printer.

The porous structure, in which many pores are intentionally placed inside the material, has excellent impact energy absorption properties. Recent studies have attempted to fabricate multi-layered porous structures with different mechanical properties within a single porous structure sample, and the mechanical properties of these structures are being elucidated. However, these studies mainly attempted to vary the densities, pore structures, and alloy compositions within a single material, such as aluminum, for the entire sample. Since multi-materials are now being promoted to utilize the most suitable material type in the right place, porous structures made of different materials, such as a combination of aluminum and resin, are expected to be required in the future. In this study, we attempted to fabricate two-layered porous structure samples of different materials by printing a resin porous structure using a 3D printer on an aluminum foam fabricated by a precursor foaming process. Static compression tests were performed on the resulting two-layered porous structure samples to investigate their mechanical properties. The resin porous structure printed by the 3D printer and the aluminum foam were both designed to expose the porous structure on the surface of the specimen so that the deformation behavior can be easily observed. The density of the resin porous structure was varied by systematically varying the filling rate of the resin porous structure to be printed, and the effect on the compression properties was investigated. The fabricated two-layered porous structure was effectively bonded between the two layers by the anchor effect, which is a mechanical bonding caused by the resin penetrating into the pores. The layers exhibited robust bonding with no evidence of separation. It was possible to fabricate a two-layered porous structure that exhibited both properties of aluminum foam and those of resin porous structure. It was found that the plateau stress in the resin porous structure layer can be controlled between about 0.5 MPa and 40 MPa, and the deformation behavior and energy absorption properties of the two-layered porous structure can be controlled by varying the resin filling rate of the resin porous structure layer. That is, it was indicated that multi-layered porous structures with various densities and consisting of various types of materials allow for the optimal design of porous structures used in structural materials.