July 21, 2017 Source: Carbon Fiber Platform

According to the official media's report, the domestic M40J carbon fiber development project hosted by the Second Division of the Second Academy of Aerospace Science and Industry Corporation was successful and “reached the international leading level”.

This news can be analyzed from a technical perspective to analyze two points.

A: The carbon fiber source of the domestic advanced satellite platform solves and relies on the dependence on abnormal channels.

Image: Carbon fiber is divided into many types, and there will be obvious performance orientation differentiation in design and manufacture.

The current domestic independent carbon fiber, the name often follows the product brand of Toray in Japan; for example, the most widely recognized T300~800 series high-strength carbon fiber, and the relatively low-profile M40J~60J series high modulus carbon fiber - or Said graphite fiber (because it has a higher carbon content).

Mx0J high modulus carbon fiber, the biggest advantage is to manufacture parts that are extremely thin and light, but not particularly easy to deform - especially in the case of extreme temperature difference changes, relying on 0 expansion coefficient to maintain dimensional stability, neither shrink nor Swell.

Figure: High-strength carbon fiber is used instead of high modulus carbon fiber for advanced aircraft.

Due to performance orientation and price issues, this carbon fiber is generally not used in aircraft manufacturing and is rarely used in missiles, mainly for the manufacture of satellite structures, especially antenna skeletons.

High modulus carbon fiber has been banned from China internationally and the blockade is very strict. Last year, the US court sued a Chinese citizen, claiming that he smuggled M60J carbon fiber into China.

Figure: High modulus fibers used to make satellites, such as main structures, solar panel brackets, antenna mounts

The domestic implementation of M40J fiber in China means that the source of manufacturing materials for the domestic advanced satellite platform has been independent and no longer needs to be obtained through abnormal channels.

Two: Aerospace Science and Industry Group does not have T800 grade carbon fiber raw yarn, only T300-700.

The current mainstream high-performance carbon fiber preparation method was invented by Kondo Kondo at the Osaka Industrial Technology Laboratory, using fine denier polyacrylonitrile fiber as a raw yarn, which was carbonized at a high temperature.

The T-series high-strength fiber, and the M-series high-modulus fiber, are the differential positioning products made by the same original yarn through different orientation processes.

Figure: The key to carbon fiber, the original silk

In fact, M40J and T300 are the same raw yarns used by Toray. In the same year (1971), the mass production was successful, and they belonged to the first generation of high-performance carbon fiber. In 1992, Toray's high modulus fiber has introduced the M70J; the earlier M60J, the strength performance is 43% higher than the M40J, and the tensile modulus performance is 50% higher than the M40J.

The important difference in composition is that the high-strength carbon fiber such as T300-T800 generally has a carbon content of 93 to 96% and a nitrogen content of 4 to 7%. The high modulus carbon fiber/graphite fiber such as M40J has a carbon content of 99.7% or more.

The difference in their key performance is that the T300 is less likely to be broken and its tensile strength is 33% higher than that of the M40J. However, the M40J is less susceptible to being pulled and deformed, and the T300 will stretch by 1.2%. M40J will only stretch 0.5%.

In the manufacture of carbon fiber, especially the development of domestic carbon fiber, the original yarn is the most terrible problem. In the 1980s, after obtaining the raw silk of Toray, China was able to produce the T300 carbon fiber finished product with comparable performance. Later, in the laboratories of major universities and institutes, until the T800 test, there was a raw silk. Can get the same level of carbon fiber products.

However, from the beginning of the test in the 1980s, until 30 years later, China completed the localization of the T300 – it has not solved the problem of performance and quality control of the raw silk.

On the carbon fiber precursor, T300-T700 and M40J use the same grade of raw silk. However, for T800 and M55J, it is necessary to use a finer denier. The Aerospace Science and Industry Group has taken out M40J grade products, which proves that its raw silk performance can only support T300-700 grade fiber.