Definition, classification and basic characteristi

2022-08-09
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Definition, classification and basic characteristics of automotive composites

automotive composites have the essence of "structure", that is, it is structure first, followed by materials. Therefore, in order to give full play to the advantages of automotive composites and promote their wide application in automobiles, we must first have a clear understanding of the definition, classification and basic characteristics of automotive composites

although the birth of fiber reinforced resin matrix composites (hereinafter referred to as "composites") has a development history of 76 years, and the birth of the world's first automobile with composite body, the Chevrolet Corvette, has a history of 55 years. In order to meet the needs of the development of the automotive industry, the automotive composite technology has also made continuous progress and new breakthroughs, so that it is more and more widely used in automobiles. However, a problem that cannot be ignored is that the promotion of automotive composite materials in the automotive manufacturing industry is still slow and ups and downs compared with other lightweight materials, which is particularly prominent in China's automotive manufacturing industry. One of the deep-seated reasons is that entrepreneurs, engineers and users in China's automotive industry, including some practitioners of automotive composites, lack a correct understanding of composites

in view of the unique understanding problems of the composite industry, Professor Zhang Ruguang, a famous composite expert in China, has written many times and shouted on different conference occasions: we should have a correct understanding of composite materials! In this regard, he cited an example: in 1988, the U.S. Congressional Office of technology evaluation published a more than 300 page Research Report for government decision-making guidance, entitled "designable advanced materials (composite materials)". In the section "reasons affecting the wider application of advanced materials", the editor pointed out that to realize the wider application of advanced materials, we should not only solve the technical problems, but also try to change the concept of people, including researchers and users, because people are always used to thinking about problems with the concept more suitable for conventional materials. This example is very illustrative and worthy of reflection. Professor Zhang pointed out that "being used to understanding composites with the concept more suitable for conventional materials" is the main reason affecting the wide application of composites. As we all know, the United States is the country with the widest application, the largest consumption and the most advanced technology of composite materials in the world, but they still believe that they still cannot correctly understand and treat composite materials, which is an important reason affecting the development of composite materials. Therefore, for China's automotive industry, which is still backward in the application of composite materials and in urgent need of catching up, only by correctly understanding automotive composites can we make good use of automotive composites and develop automotive composites better and faster. From this perspective, this serial article is specially listed in a separate article to introduce the definition, classification and basic characteristics of automotive composites in detail, so as to deepen readers' understanding of automotive composites

definition of automotive composites

many experts believe that at present, mankind has entered the era of composite materials from the era of synthetic materials, and this formulation has a certain scientific basis. Because it is very difficult to synthesize a new material to meet the comprehensive indicators of various high-performance requirements. Even if a satisfactory material is developed, the investment and cycle from laboratory to large-scale production are daunting. However, if the existing materials are combined, it is possible to achieve twice the result with half the effort. It is under the guidance of this technology research and development that composites flourish. At the same time, it also creates many characteristics and properties different from conventional materials. So what kind of material is composite? What should be its correct definition? How should we correctly understand and recognize it

according to the definition of composite by the international organization for standardization, composite is a multiphase solid material composed of more than two substances with different physical and chemical properties. The national standard gb/t defines it as a solid material composed of two or more independent physical phases, including bonding material (matrix) and granular, fiber or sheet materials, which is called composite material. Although the international organization for standardization and China's national standards are different in text organization, the basic content of the definition is the same. According to its definition, we can recognize and understand composites from the following aspects

1. Composite material has a broad category, which does not specify which specific materials it is composed of, nor does it limit the material composition of materials, but only defines the combination of more than two materials, which is a concept of material use method. Therefore, we can imagine that composite materials should be all inclusive and can be designed into a variety of material properties, which provides infinite space for our innovation and development

2. The components of composites and their relative contents are artificially selected and designed, and are artificially manufactured rather than naturally formed, which helps us to distinguish natural composites with some composite morphological characteristics

3. Although the components of composites can be diverse, they must be relatively independent, that is, they still maintain their inherent physical and chemical properties after compounding, which is different from materials such as compounds or alloys as we know

4. The properties of composites depend on the synergy of the properties of each component material, which is not a simple addition of the properties between the components, but has important significance for improvement. Therefore, composite materials have new, unique and usable properties, which are inferior to or different from those of single component materials. It should be a kind of designable material

5. Composites are multiphase materials with obvious interface between components. The component materials are divided into reinforcement phase and matrix phase, which are distinguished according to the physical and chemical properties of their components and the morphology in the final composite. The reinforced phase component is usually in the form of fiber (continuous or chopped), sheet or particle, with high strength, modulus, hardness and brittleness. It is the main bearing body when the composite bears external load. It is also called "dispersed phase" because it is dispersed in the composite and is isolated and surrounded by the matrix phase. The matrix phase component is a relatively soft and ductile connective material surrounding the reinforcing phase. In composites, there is an obvious interface between reinforcement phase and matrix phase, which is called "composite interface". Because the interface of the composite is located between the reinforcement phase and the matrix phase, and the two phases are connected with each other, and the chemical composition and mechanical properties are obviously different from the adjacent two phases, which can play the role of load transfer, it has a great impact on the performance, failure behavior and application efficiency of the composite

what the above definition and interpretation stipulate is composite materials in a broad sense, including not only polymer matrix (resin) composites, but also metal matrix composites, ceramic matrix composites, carbon/carbon composites, cement-based composites, etc. Among them, polymer matrix (resin) composites are the most widely used, with the most varieties and the highest output, and occupy an important position in composites. In polymer matrix (resin) composites, what is the market size of automotive carbon fiber composites after 10 years? Dimensional reinforced polymer matrix (resin) composites are also one of the most widely used, the most diverse and the highest yield. They occupy an important position in polymer matrix (resin) composites. Therefore, people are used to calling fiber reinforced polymer matrix (resin) composites "composites" for short, while other composites are given full names

in the automotive industry, this kind of resin matrix composite with fiber as the reinforcing phase is also mainly used at present. Therefore, the "automotive composite" referred to in this paper is "fiber reinforced resin matrix composite". From this, we come to the definition of automotive composites: fiber reinforced resin based composites that can meet the annual death toll of 111000 people caused by decoration pollution in China and meet the needs and technical performance indicators of the automotive industry. Recently, due to haze weather, composites are "Automotive composites"

classification of automotive composites

although it has been made clear that "fiber reinforced resin matrix composites that can meet the needs and technical performance indicators of the automotive industry" are automotive composites, there are still many classification methods according to different starting points. For example, it can be classified according to the nature or number of matrix resins, the type, shape or arrangement of reinforcing fibers, and the use function, etc

1. The classification according to the properties of matrix resin includes: fiber reinforced thermosetting resin based automotive composites, involving: fiber reinforced unsaturated polyester resin based composites, fiber reinforced epoxy resin based composites, fiber reinforced phenolic resin based composites, fiber reinforced vinyl ester resin based composites, fiber reinforced polyurethane based composites, etc; Fiber reinforced thermoplastic resin matrix automotive composites, including fiber reinforced polypropylene matrix composites, fiber reinforced polycarbonate matrix composites, fiber reinforced polyimide matrix composites, fiber reinforced polyformaldehyde matrix composites and fiber reinforced polyvinyl chloride matrix composites

2. The classification according to the number of resins includes: fiber reinforced single resin based automotive composites and fiber reinforced hybrid resin based automotive composites

3. The classification according to the types of reinforcing fibers includes: glass fiber reinforced resin based automotive composites, carbon fiber reinforced resin based automotive composites, aramid fiber reinforced resin based automotive composites, and natural plant fiber reinforced resin based automotive composites

4. The classification according to the length of fiber reinforced materials includes: continuous fiber reinforced resin based automotive composites, long fiber reinforced resin based automotive composites and short fiber reinforced resin based automotive composites

5. The classification according to the number of fiber reinforced materials includes: single reinforced material resin based automotive composites and hybrid reinforced material resin based automotive composites

6. Classification according to service performance includes: structural fiber reinforced resin based automotive composites and functional fiber reinforced resin based automotive composites

7. According to the characteristics of fiber reinforced materials and the range of matrix used, the classification includes: traditional fiber reinforced resin based automotive composites and advanced fiber reinforced resin based automotive composites

the multifunctional composite roof made with SM, such as computer C process, is used in Citroen's bellingo car

basic characteristics of automotive composites

compared with traditional materials such as steel, iron, aluminum, plastic and rubber, automotive composites are another kind of new materials completely different. Unlike traditional materials, which have uniform and isotropic materials, it presents heterogeneous anisotropy. To be exact, automotive composites should first be a structure, followed by a material. In that case, what are the differences between automotive composites and traditional automotive materials<

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