Recently, Boeing is developing a continuous resin-based composite 3D printing technology to manufacture composite products through photocuring technology.
Design materials based on performance requirements. The basic principle includes a continuous 3D printing process by pushing the movement of the wire by a conveying mechanism, wherein the wire comprises a non-resin component and a photopolymerizable resin component. The feed mechanism includes opposing rollers and a doctor blade in contact with at least one opposing roller.
A continuous flexible wire is deposited along the print path by the transport guide, and then a portion of the continuous flexible wire deposited along the print path provides curing energy by removing the residue of the photopolymerizable resin component by using a doctor blade.
The continuous flexible wire comprises a prepreg composite and a non-resin component, including one or more fibrous materials such as carbon fiber, glass fiber, synthetic organic fiber, aramid fiber, natural fiber, wood fiber, boron fiber, Silicon carbide fiber, fiber, fiber braid, wire, wire, etc. The continuous flexible wire is laminated with a plasticizer to make a composite part.
Which material is used depends on the physical properties that need to be achieved, including strength, stiffness, flexibility or hardness. However, in addition to strength, hardness, flexibility, hardness considerations, sometimes can be extended to the precise choice of color, luminescence, electrical conductivity, thermal conductivity and so on.
In the process of processing, in addition to ultraviolet rays to cure the polymer resin, infrared light or X-rays may also be used.
Perhaps you will wonder why Boeing wants to develop such materials. When Boeing announced that it would use more than 600 3D printed parts for Boeing's Starliner space taxi, it also means that plastic instead of lightweight metal alloys will become a vehicle. A major trend in the field.
Boeing's continuous resin-based composite 3D printing technology is not only suitable for aerospace applications, but also for other industries, such as vehicles, marine vehicles, spacecraft and other applications.
The 3D printing method of continuous fiber reinforced resin-based composite materials on the market has the following main problems:
- When the fibers of the various types are delivered, their surface active groups are only suitable for the infiltration process with the thermosetting resin. When the untreated fiber is blended with the molten thermoplastic resin using a simple measure, it is difficult to sufficiently wet the fiber and the resin, which results in a poor fiber-resin interface of the member.
- The large tow fibers are flattened, and the existing 3D printing method is difficult to use large tow fibers, and the small tow fibers are slow in forming during molding, and the surface quality, fiber resin volume fraction, and fiber resin distribution after molding Performance indicators such as conditions and inter-layer bonding are difficult to control.
- The existing method in the printing process, due to the partial branching and breaking of the fiber, it is easy to cause the fiber to accumulate and block in the cavity, which affects the molding process, and at the same time, the fiber in the forming track is loose and irregular. The bearing performance of the component is affected.
In China, Nanjing University of Aeronautics and Astronautics uses 3D printing for existing thermoplastic resin matrix composites to form a small connecting fiber, and can not effectively impregnate the connecting fibers, resulting in low molding speed and large component size. The 3D printing method of continuous fiber reinforced thermoplastic resin-based composite material was invented by the problem of low comprehensive performance of molded parts. Suitable for large-sized fiber tows, the printing technology has a high molding speed, improved surface quality, good interface bonding between fibers and thermoplastic matrix, high fiber content, high fiber density, and improved mechanics of printing members. .
Nanjing University of Aeronautics and Astronautics has also developed a continuous fiber reinforced thermoplastic resin matrix composite rotary blending 3D printhead, which is characterized in that: the extrusion head is connected to the melting chamber and can also rotate around the central axis, and the direction of rotation is opposite to the melting chamber; the melting chamber There is a stirring tooth ring on the inner side of the extrusion head, the fiber bundle and the molten thermoplastic resin are evenly blended by the two-stage reverse rotation spiral tooth ring, and the blend is tightly wound into a cylindrical tow by a spiral, resin Uniform distribution along the fiber orientation; the extrusion head extrudes the material to the forming zone and solidifies into a fiber reinforced resin matrix composite.
The technology of Nanjing University of Aeronautics and Astronautics is a breakthrough for the current thermoplastic composite molding technology. Nanjing University of Aeronautics and Astronautics uses a two-stage rotating cavity to stir and entangle the blend of fiber and resin, which is suitable for larger size fiber tows. Optimize the adaptability of the print head to the original state of the fiber, improve the printing efficiency and improve the surface quality of the component at the same printing speed; under the action of stirring and blending, the infiltration between the fiber and the resin is sufficient, and the blending is performed. The fibers in the body are tightly spirally wound, which improves the bearing capacity of the reinforcing body, and the resin is evenly distributed throughout the fiber, improving the interlayer and interface bonding properties of the member, and improving the mechanical properties of the printing member; The rotation can make the blend of the fiber and the resin uniform after the extrusion, and the fiber volume is high.
Currently, in the field of continuous fiber reinforced thermoplastic composite molding FDM printing technology, active enterprises and research institutions include Mark Forged, University of Japan, Tokyo Institute of Technology, and Xi'an Jiaotong University. 3D printing With Nanjing University of Aeronautics and Astronautics pushing this level of technology to a new level, we believe that FDM technology for continuous fiber reinforced thermoplastic composite printing technology is further moving towards industrial applications.
The breakthrough of Nanjing University of Aeronautics and Astronautics is to achieve high mechanical properties of 3D printing of continuous fiber reinforced thermoplastic matrix composite components, with high molding efficiency and good surface quality, which can be applied to the molding of aerospace complex components with high performance requirements. process.
The transition from metal to high-performance materials is currently a established trend in the aerospace market, and composite plastics are the solution to design freedom, ease of manufacture, and lightness beyond traditional aluminum.
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