Carbon Fiber Composite Material Production Technology Starting From The Carbon Fiber Composite Material Manufacturing Process Of Resin Raw Materials and RTM Production Process

 

Carbon Fiber Composite Materials are an emerging material industry that is being developed in my country’s “13th Five-Year Plan”. They have a wide range of applications in the civil and defense fields and are an irreplaceable important strategic material in my country’s economic and technological development. The production technology of carbon fiber composite materials not only affects the quality of composite materials, but also directly affects the production cost, so it has attracted much attention.

 

Based on the needs of industry development, the Carbon Fiber Composite Material Research Group of the Patent Analysis Popularization and Promotion Project of the State Intellectual Property Office conducted an in-depth analysis of the production technology of carbon fiber composite materials from the perspective of the manufacturing process of carbon fiber composite materials of resin raw materials and RTM production process.

 

PART1 – Thermoplastic Resin Raw Materials

 

The most common resin matrices of thermoplastic resin-based carbon fiber composite materials are the following seven thermoplastic resins: polyamide, polycarbonate, polypropylene, polyphenylene sulfide, polyetheretherketone, polyetherimide, and polyetherketoneketone. As of August 2015, there were 7,186 global patent applications involving these seven types of thermoplastic resin-based carbon fiber composite materials. As can be seen from Figure 1 below: polyamide, polycarbonate and polypropylene-based carbon fiber composite materials have the largest number of patent applications.

 

Among the seven types of thermoplastic resin-based carbon fiber composite materials, polyamide-based carbon fiber composite materials have the largest number of patent applications, and the patent application began in the 1980s. It is also one of the earliest thermoplastic resin-based carbon fiber composite materials that have received attention. Among all the patent applications for polyamide-based carbon fiber composite materials, there are 1,096 patent applications that focus on the interface bonding between carbon fiber and resin matrix.

 

Figure 2 below is a global patent application efficacy chart of Chinese and foreign applicants in the interface bonding of polyamide-based carbon fiber composite materials, showing that Chinese applicants pay less attention to the means of modifying the resin matrix, and both Chinese and foreign applicants focus on improving the mechanical properties, stability, toughness and wear resistance of carbon fiber composite materials through technical means of improving additives.

 

1. Foreign applications are patent applications filed by foreign applicants, and Chinese applications are patent applications filed by Chinese applicants.
2. Fiber surface modification refers to any modification of the surface of carbon fibers, including sizing agent coating, fiber surface oxidation etching, etc.
3. Resin matrix improvement refers to the modification of polyamide resin, including grafting modification, physical property improvement, etc.
4. Additive improvement refers to other additives in the composition forming the composite material except carbon fiber and polyamide resin.
5. Process improvement refers to the improvement of the process of forming the composite material by the composition.

 

Figure 3 below shows the domestic application of Chinese and foreign applicants using additives to improve the performance of polyamide carbon fiber composite materials. There are 115 patent applications filed by domestic applicants involving the improvement of the mechanical properties of polyamide-based carbon fiber composite materials by additives. There are 27 patent applications filed by foreign applicants involving the improvement of the mechanical properties of polyamide-based carbon fiber composite materials by additives.

 

The most commonly used additive in domestic applications is antioxidant, followed by lubricant. In order to solve the problem of low toughness of composite materials after adding carbon fiber, domestic applications use toughening agents and compatibilizers more frequently, that is, domestic applicants usually use these two additives at the same time. The method of using elastomer to toughen polyamide-based carbon fiber composite materials usually requires the interfacial compatibility and dispersion of the elastomer dispersed phase and the polyamide matrix. One of the effective means to solve this problem is to melt-graft the elastomer with compounds containing polar functional groups such as maleic anhydride (MAH). For example, Chinese patents CN101139462 A and CN102863776A disclose a modification method of adding maleic anhydride grafts, such as one or more of EPDM, POE, SBS, and SEBS to SEBS grafted with maleic anhydride in the polyamide matrix. This method achieves a good toughening effect.

 

The toughening agent and compatibilizer commonly used in domestic applications are maleic anhydride grafts. The most commonly used additives by foreign applicants are other inorganic fillers. Among the 27 patent applications, 12 add other inorganic fillers, followed by 7 patent applications for adding other resins.

 

 

PART2 – RTM Molding Process

 

Resin transfer molding (RTM) is one of the composite molding processes developed in recent decades, with the advantages of low cost, high efficiency and good quality. Figure 4 below shows the technical composition of global patent applications for the RTM process, with reinforcement and mold innovation as the technical focus, followed by improvements in resin systems and composite material structure design.

 

The technical solutions of 577 global applications for RTM process are analyzed, and Figure 5 (Technical efficacy analysis of global patent applications in the field of RTM) is obtained. Figure 5 shows that improving mechanical properties, reducing costs, achieving lightweight, shortening production time and sufficient impregnation are the technical effects that the industry is currently paying more attention to. Among them, the means to improve mechanical properties mainly include the improvement of reinforcement fiber materials, the selection and compatibility of resin composition components, the improvement of molds and the design of composite material structures. Cost reduction is mainly achieved through the improvement of molds, such as reducing the number of parts and increasing the degree of integration. The use of fiber reinforcement materials such as carbon fibers with different dimensions, axial directions, structures and surface modifications is the most important means to achieve lightweight. The main means of sufficient impregnation and shortening production time are reinforcement, resin system, mold and injection conditions.

 

In addition, the production time is composed of a series of time such as laying time, injection time, impregnation time, curing time, demoulding time, etc., and the factors affecting each component further affect the length of production time. There are few patents related to shortening curing time and increasing fiber volume content, which may be caused by the late start or greater difficulty of research in the above two fields. With the development of the automotive and aerospace fields, improving mechanical properties, achieving lightweight and reducing costs are still hot spots in the industry. Among them, shortening the curing time to reduce costs is one of the most concerned focuses in the automotive field. As can be seen from the efficacy diagram, the resin system is the main factor and means to shorten the curing time.

 

Figure 6 shows the companies and activities of the major global R&D teams in the RTM field. The figure shows that the LA FOREST MARK L, MURDIE NEIL, and SIMPSON ALLEN H teams belong to Honeywell (USA). The application period lasted from 2000 to 2012. The R&D fields mainly involve reinforcements, molds, and resin systems, among which LA FOREST MARK L is the most active. The R&D team led by LA FOREST MARK L is mainly committed to the research in the field of carbon-carbon composite materials, including methods and densification equipment for rigidification and densification of preforms, impregnation of low-viscosity resins, etc.

 

Around 2008, a patent for high-temperature welding technology for glass fiber and metal was applied.

In 2011, the densification and rigidification of carbon-carbon composite materials began to be studied.

In 2011, a patent for low-viscosity resin infiltrated carbon-carbon composite materials was applied.

In 2013, a composite material and method including ceramic particles were applied.

 

In 2014, an invention patent for densification of carbon-carbon composite materials by using condensed polynuclear aromatic hydrocarbon resins was applied.

 

The team of GERARD PIERRE and GLOTIN MICHEL belongs to Arkema France. The application time is from 2011 to 2013. It should be a relatively young team and is in an active period. The research and development areas are mainly resin systems and reinforcements. The research and development team led by GERARD PIERRE is currently active in the research and development of resin systems.

 

The research areas before 2011 included UV-curable sealant compositions based on acrylic/methacrylic block copolymers, photovoltaic modules, power distribution systems, etc. In 2011 (priority date), a patent for composite materials obtained by in-situ polymerization of thermoplastic resins and fiber materials was applied.

 

In 2011, a method of impregnating a carbon fiber substrate with a viscous liquid containing methacrylic acid or acrylic acid compounds was studied for use in the field of reinforced composite materials. It also involved the field of additives for polymer filtration membranes (jointly applied by Arkema and other companies). The team of Liu Gang and Yi Xiaosu is from the Beijing Institute of Aeronautical Materials of Aviation Industry Corporation of China. They applied mainly from 2011 to 2013 and are currently the most active team. Their main research and development areas are resin systems and reinforcements.

 

 

Carbon Fiber Composite Materials Research Group Of The National Intellectual Property Administration’s Patent Analysis Popularization And Promotion Project