Misunderstandings of the hottest automotive carbon

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Misunderstanding interpretation of automotive carbon fiber materials

referring to the heavy and long-term problem of automotive lightweight, the term "carbon fiber" seems to have to be said. It is a common impression of people that it is strong, lightweight and iconic texture; At the same time, high pollution, high technology and high price are also objectively criticized; However, before discussing the contradiction, it is more necessary for us to clear up some misunderstandings and habitual cognitive errors. Today we will talk about this not novel material technology achievement

common misconception 1: think that many supercars use carbon fiber

key point: mistakenly confuse carbon fiber and carbon fiber reinforced composite materials

Corvette first used glass fiber

in 1953 to use man-made fiber materials in the production of cars for a long time. Now almost all front-line manufacturers have cars made of carbon fiber materials

carbon fiber and carbon fiber reinforced composites

the relationship between the two is like flour and dry food, that is, everyone knows carbon fiber raw materials, but producing high-performance composites according to demand is the difficulty and key point

in addition, in terms of physical composition, carbon fibers are almost all composed of "carbon" (usually the thinner the design thickness is, the more than 95%), while reinforced composites need to add many elements to meet higher use requirements. The most common ones are polypropylene based fibers, viscose fibers and asphalt based fibers, which have different characteristics and grades. We will introduce them later

almost all carbon fibers used in automobile manufacturing are CFRP

carbon fibers are almost all composed of "carbon" (usually more than 95%). They are fibrous carbon materials, and composites are usually combined with resins

in addition, from the perspective of appellation, the English abbreviation of carbon fiber is CF, while the English abbreviation of carbon fiber reinforced plastic is CFRP, For example, the Volkswagen XL sport hybrid performance car just unveiled at the Paris auto show and the BMW I series models just launched in China all use CFRP, that is, the body body body made of carbon fiber reinforced composite materials

common misconception 2: referring to carbon fiber is considered to be a high-grade material

key point: carbon fiber materials can also be divided into high and low grades, mainly related to manufacturing technology

when referring to carbon fiber materials, the first thing we can think of is that they are solid, light and expensive (compared with traditional steel and plastic materials), of course, this is not bad, Because the carbon fiber materials that can be applied to performance vehicles and even F1 racing cars are indeed high-end products. However, this does not mean that there are no low-end products for carbon fiber products. The key to distinguish between high-end and low-end products is the production quality and manufacturing process

in fact, carbon fiber is only a material definition in a broad sense. In fact, there are many composite materials derived from application needs, and there are many dimensions of classification, such as precursor type, physical properties, application functions, manufacturing methods, and so on. Accordingly, there are high and low grades. Here, according to the type of precursor, there are usually polypropylene based fiber, viscose fiber, asphalt based fiber and other types. Without raw materials, it means that the carbonation yield is different. Among them, the output of carbon fiber produced by polypropylene is the largest (accounting for about 95% of the market), and its carbonation yield is about 50% - 60%, which belongs to a relatively high range. With asphalt fiber as raw material, the carbonation yield can reach%, and the cost is lower, which is also a type of active development at present

another problem that determines the use and grade of carbon fiber is the manufacturing process. The simplest thing is that we all know that the production of carbon fiber materials usually requires ultra-high temperature heat treatment steps (usually in the order of 300 ℃ -2000 ℃), and different firing temperatures will directly affect the cost of product characteristics, so the price difference between different carbon fiber materials may be several times or even dozens of times. In addition, high-temperature firing often means a lot of energy consumption. Of course, this belongs to the dimension of environmental protection, which we won't mention for the time being

common misconception 3: because of the similar texture, it is considered that carbon fiber material and Kevlar material are the same

key points: the physical properties and intellectual property ownership of the two are essentially different

Kevlar became the registered trademark of DuPont in 1972

Wang Zhonghui said that according to the different chemical formulas, aramid fiber materials can be divided into counterpoint and meta. Kevlar is the counterpoint aramid brand of DuPont, Aramid brand is Nomex

during a visit to BMW X5 bulletproof car, the communication between the audience on site. In addition, a friend asked at that time: the annual output of carbon fiber materials is large, while the annual output of Kevlar material is much smaller. Why use Kevlar instead of carbon fiber for bulletproof materials

carbon fiber has been introduced previously, which is actually a fibrous carbon material; Kevlar fiber material is the brand name of American DuPont company for aramid fiber material products, and its chemical name should be: poly-p-phthaloyl-p-phenylenediamine. Because it belongs to man-made fiber materials and has similar process flow, it does have similarities in visual perception, but it is actually different

the most direct way to see the characteristics of reactive materials is to look at the application. For example, Kevlar material will be used in ordinary bulletproof armor or even the bulletproof armor of tanks instead of carbon fiber material. The important reason for this is that Kevlar material has better toughness and can use better plastic deformation to absorb external impact energy; Carbon fiber is brittle. When the external energy exceeds the limit value, it will break. There is a professional comparison term called "modulus" (similar to spring coefficient). Undoubtedly, Kevlar's modulus is higher than that of carbon fiber materials

firstly, carbon fiber reinforced composites are the practical application of carbon fiber, which are interdependent but not at the same level; At the same time, carbon fiber materials are the same as other materials, but they are also good or bad, but most of the time, what we see on performance vehicles are high-end products; In addition, compared with Kevlar material, they do have something in common, and both of them are made of high-strength man-made fiber. However, this testing machine can be used to conduct pin disk or ball disk experiments pointed out in the Standards ASTM g 99, DIN 50324 and iso/dis 7148 ⑵, which are still not equivalent to each other

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