3D printing of integrated composite honeycomb sandwich structures with continuous carbon fiber

In the coming years, it is expected that the application of composite in the aerospace and automobile industry will be increased through the development of 3D printing technology using carbon fiber-reinforced resin. Sandwich structures currently used in aerospace components are formed of a skin material and a core material adhered to each other to form an integral structure. In these structures, it is necessary to thoroughly investigate the functional characteristics of the core material and shape it in the best way to take full advantage of its unique characteristics. Therefore, in this research, we investigate the possibility of designing and fabricating a free-form core shape, and investigate the feasibility of molding these integrated sandwich structures using a 3D printer capable of laying continuous carbon fibers. In the proposed experimental method, the diameter of the filament is smaller than that used in a general FDM-type 3D printer; to accommodate thin filaments in the molding process, we modified a 3D printer accordingly. As continuous carbon fiber 3D printers have a simple arrangement without a cutting mechanism, all shapes molded must be formed under single-stroke writing conditions. Therefore, in forming the core material in this research, the unit cell must satisfy the periodic boundary condition, making one-stroke molding possible. Notably, the tension in the continuous carbon fiber enables the formation of wide bridge spaces without the support material. Experimental results show that it is both possible to design core shapes such as a honeycomb structure freely and to mold integrated sandwich structures using the proposed method.