In addition, the recycling of thermoplastic carbon fiber composite resin based carbon fiber composite, instead of aluminum alloy, has become one of the important symbols to measure the advanced of aircraft. According to the base resin, resin based carbon fiber composite can be divided into two categories: thermosetting carbon fiber composite and thermoplastic carbon fiber composite. No matter what kind of material, in the process of manufacturing the machine body, it is necessary to produce corners and surplus materials. The figure below shows the 787 nose section. During the manufacturing process, the door and window openings shall be cut. The cut materials become corners and surplus materials.
Boeing 787 nose section skin laying completed, ready to enter autoclave for curing
Head section after door and window opening cutting
It is difficult to recover thermosetting carbon fiber composite. In the early years, centralized landfill was adopted. With the improvement of people's awareness of environmental protection, in 2004 most EU member states passed laws banning landfill treatment of composite materials. In addition, incineration of plastics is not feasible due to the potential release of toxic by-products. On September 18, 2000, the European Parliament issued in 2000 and adopted by the EU member states in November 2003, the EU end of life vehicle (EEEV) Directive requires that 95% of every vehicle manufactured after January 2015 must be reused or recycled. At present, the commercial methods of removing resin from thermosetting carbon fiber composite are pyrolysis (heat treatment) and solvent decomposition (chemical treatment). As for the leftovers and wastes in the production of thermoplastic carbon fiber composite materials, as well as the discarded aircraft body in the future, as long as the resin is heated to melt, the carbon fiber and resin can be decomposed. This process is simple and easy to operate, and will not cause pollution to the environment. "New 320" lower half fuselage test piece, 8 meters in length and 4 meters in diameter. There are 13 frames, 36 long trusses, 500 saddle shaped connectors, 270 system supports and clamps. Saddle shaped connectors, system supports and clamps are all made of recycled thermoplastic composite corner surplus materials. The manufacturing process adopts injection molding, molding or 3D printing. For 8 m upper fuselage test pieces, at least 400 saddle shaped connectors shall be used,. The new 320 is more than 30 meters long. So many saddle shaped connectors, system supports and clamps are made of recycled materials, which not only protect the environment, but also reduce the cost of aircraft manufacturing.
Editor's note: according to the data of using thermoplastic carbon fiber composite in "new 320", it has been reported in detail through several short articles. At present, the research and development work is still in progress. Here are some key technology projects that we hope to share. 1. Adapt to the structural design of thermoplastic carbon fiber composite materials (fuselage design separation surface, connecting parts, parts bearing concentrated load, integrated design with system parts). The wing structure is still covered with a layer of veil); 2. Manufacturing process: A. welding process and welding equipment. Especially the accessibility of welding equipment, welding speed and random inspection; B. tooling, mold. The RTM mould and skin laying mould for manufacturing parts must withstand a high temperature of about 400 ° C. "Jig less" and "adaptive assembly" are used for assembly tooling. NDT process and equipment in the process. All of the above processes need to be automated. 3. Thermoplastic carbon fiber composite. At present, three kinds of thermoplastic carbon fiber composites are used in the manufacture of test pieces: CF / PPS, CF / PEEK and CF / PEKK. These three kinds of carbon fiber composite materials have not yet registered trademark market-oriented products. The combination of carbon fiber and resin is still under exploration, such as whether the surface of carbon fiber is pasted or not. At present, there are only a few international manufacturers that can commercialize peek and PEKK. Peek and PEKK produced by different manufacturers have different properties. When they are combined with carbon fiber from different manufacturers and with different strength properties, the properties of the composites are completely different. The current situation of thermoplastic carbon fiber composite for civil aircraft is a good time for us to participate! Appendix: comparison of Chinese and English nouns:
Note: a kind of flexible aircraft assembly frame without fixed foundation used by jig less Airbus. -------End: Yang Chaofan, senior expert in aircraft manufacturing, specializes in civil aircraft composite materials in recent years. The first batch of researcher level senior engineers of the former Ministry of aviation industry enjoy the special allowance of the State Council.
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[materials] Yang Chaofan's exclusive interpretation of composite materials and manufacturing technology
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