It is understood that Boeing recently is developing the 3D printing technology of continuous resin matrix composite, and manufacturing composite products through photo curing technology. Its basic principles include the movement of silk material through the conveyor mechanism to achieve a continuous 3D printing process, in which the silk material includes non-resin components and optical polymerization resin components. The feed mechanism comprises a relative roll and a scraper in contact with at least one relative roll.
A continuous flexible filament is deposited along the print path through a conveyor guide. It provides curing energy along with a part of a continuous flexible filament deposited, removes the residue of the light polymerization resin component by scraper.
181125-1-update continuous flexible filaments include prepreg composites and non-resin components, and include one or several fiber materials such as carbon fiber, fiberglass, synthetic organic fibers, aromatic polyamide fibers, natural fibers, wood fibers, boron fibers, silicon carbide fibers, fiber optics, fiber knitted fabrics, metal wires and so on. Continuous flexible wire cascades with plasticizer to manufacture composite components.
The specific material needs to be determined according to the physical characteristics required. These physical characteristics include strength, stiffness, flexibility or hardness. In addition to above considerations, some aspects can also be taken into account, like color, luminescence, conductivity, thermal conductivity and so on.
In addition to the use of ultraviolet light to solidify polymer resins, infrared or X-rays can also be used in the processing.
Perhaps you will wonder why Boeing is developing such materials. In fact, Boeing announced the application of more than 600 3D printing parts for Boeing’s Starliner Space taxi, which also means there is a major trend that plastic replace lightweight metal alloys in the field of transportation.
However, according to market research, a continuous resin matrix composite 3D printing technology that Boeing developed is not only suitable for aerospace applications, but also can be used in other industries. It can be used in vehicles, maritime transport, spacecraft and other applications.
The 3D printing method of continuous fiber reinforced resin matrix composites on the market has the following main problems:
When all kinds of fibers are out of the factory, their surface active groups are only suitable for the infiltration process with thermosetting resins. When using simple measures to blend untreated fibers with molten thermoplastic resins, it is difficult to fully infiltrate the fibers with resins, which results in poor fiber-resin interfaces of the components.
Large silk beam fiber is flat ribbon. The existing 3D printing method is difficult to use large wire bundle fiber, and molding speed of small wire beam fiber is slow. What’s more, its surface quality, fiber resin volume fraction, fiber resin distribution, interlayer Junction and other performance indicators are difficult to control.
In the printing process, due to the local bifurcation and fracture of the fiber, it is easy to cause the fiber to accumulate and clog in the cavity, which has a negative impact on the molding process. At the same time, is loose, irregular distribution state of the fiber in the molding trajectory will affect the bearing performance of the component.
According to market research, in China, A 3D printing method for continuous fiber reinforced thermoplastic resin matrix composites was invented by NUAA (Nanjing University of Aeronautics and Astronautics) for the problems of existing thermoplastic resin matrix composite 3D Printing molding, like small connection fiber size, low molding speed( because we can not achieve effective impregnation of the connected fibers), large component size constraints, and low comprehensive performance of molded parts. This method is suitable for larger fiber wire bundles, and it has quick printing technology molding speed as well as improved surface quality. At the same time, the combination performance between fiber and thermoplastic matrix interface is good; component fiber content is high; fiber compactness is high; and the mechanics of printing components is also improved.
Aeronautics and Astronautics also developed a continuous fiber reinforced thermoplastic resin matrix composite rotary blended 3D printhead, characterized in that: extrusion head connected to the molten cavity can also be rotated around the central axis, and the rotation direction is the opposite of the molten cavity, and the molten cavity and the inside of the extruder have a stirring tooth ring, Fiber bundles and molten thermoplastic resins are evenly blended under two-stage reverse rotating spiral ring agitation, and the blends are tightly entangled into cylindrical filaments, and the resins are evenly distributed along the fiber orientation, and the extrusion head extrusion material is to the molding area and solidified into a fiber reinforced resin matrix composite material.
NUAA’s technology is a breakthrough for the current thermoplastic composite molding technology. NUAA uses a two-stage rotating cavity to stir and wrap the fiber and resin blends, which is suitable for larger size fiber filaments, optimizes the printhead’s adaptability to the original state of the fiber, and Improving the printing efficiency at the same printing speed, and improving the surface quality of the components; Under the action of agitation and blending, the fiber is fully infiltrated with resin. The fibers in the blends are tightly spiral winding, which improves the bearing capacity of the reinforcement body. The resin is evenly distributed throughout the fiber, which improves the interlayer and interfacial bonding performance of the components and improves the mechanical properties of the printing components. The rotation effect of extrusion can make the distribution of fiber and resin uniform and the volume content of fiber is high.
At present, active enterprises and research institutions for continuous fiber reinforced thermoplastic composites molding FDM printing technology include the MarkForged in the United States, Japan University, Tokyo Institute of Technology, Xi ‘ an Jiaotong university and so on. NUAA push 3D Printing up to a new level. FDM technology for continuous fiber reinforced thermoplastic composite printing technology will further towards industrial-grade applications.
NUAA’s breakthrough lies in the realization of high mechanical properties of continuous fiber reinforced thermoplastic matrix composite components of 3D printing, and high molding efficiency, good surface quality. It can be applied to the molding process of aerospace complex components that requires high performance.
It is an established trend that metals transform to high-performance materials in the aerospace market. Composite plastics surpass traditional aluminum and become a program that pursues design freedom, manufacturing convenience and lightweight.
