Do you understand? The world of carbon fiber is so amazing!

Carbon fiber is a lightweight and high-strength material. There are many carbon fiber material components in cars and aircraft. It can be used to make almost anything, bicycles, golf clubs and even wallets can be made from carbon fiber. However, due to the complexity of its preparation process and the high cost of raw materials, carbon fiber is currently not widely used.

1. Complex process

Carbon fiber can also be called a “composite material”. It is a very delicate material with very excellent properties. At the same size, carbon fiber is often harder and less dense than metal, which is why carbon fiber is often used in body panels and jet turbines. The property of hardness actually includes many measurement indicators. Specifically, carbon fiber’s tensile strength (i.e., its ability to resist stretching) is four times that of steel and eight times that of aluminum. And its ability to resist bending is much greater than steel and aluminum. Moreover, although carbon fiber is very strong, its mass is not heavy. On the contrary, the mass of carbon fiber is only one-third of the same volume of steel.

The excellent performance of carbon fiber is due to its composition and the glue or epoxy resin added during preparation. Carbon fiber is made of treated carbon filaments, and the thickness of the carbon filaments is thinner than human hair. The epoxy resin added during preparation allows the various materials to be thoroughly mixed and “hardened”. The preparation methods are similar, and they all need to go through the above-mentioned “raw silk preparation and sizing” process.

Raw filaments without added resin cannot be called carbon fiber. Carbon fiber is soaked in epoxy resin and shaped into shape. The raw filaments in the long spools are cold-treated to prevent the resin from solidifying, and when these raw filaments are placed on the surface of the mold, the machine will instantly heat it to solidify it immediately.

After the raw fiber preparation and sizing treatment, the product is truly ready when the carbon fiber is solidified. During the curing process of carbon fiber, a chemical reaction may occur, generating substances that do not contain carbon in the original fiber material, resulting in a stronger agglomeration force between fiber particles.

Turbine components made of carbon fiber materials

2. Why is it “carbon” fiber?

Carbon fiber is often irreplaceable where stiffness and lightness are required. This may be due to the characteristics of carbon atoms. Scientific research shows that carbon atoms can easily form bonds with other atoms.

Carbon is a very interesting element. The hard thing in nature (diamond) is a simple substance of carbon, and one of the substances with low hardness (graphite) is also a simple substance of carbon. Generally speaking, the physical properties of materials made from carbon are the same as those made from other elements, and they are all related to the way atoms/molecules form bonds and the way atoms/molecules agglomerate.

The way carbon atoms form bonds determines the properties of the material.��. For graphite materials, carbon atoms are stacked layer by layer. The bonds between carbon atoms on the same plane are very strong, but the bonds between carbon atoms between planes are relatively weak, which makes graphite materials very easy to separate (and also makes Graphite conducts electricity very well). For diamond, the bonds formed by carbon atoms are three-dimensional, and the unit cell belongs to a tetragonal lattice. Although the bond energy of a single bond is lower than that of graphite, its bond energy is the same in all directions (except for surface atoms). , so the material appears much harder overall.

The unit cell of graphite belongs to the hexagonal crystal system

Among the raw materials used in the preparation of carbon fiber precursors, polypropylene cyanide fiber, or “PAN”, is commonly used, which is composed of three elements: C, H, and N. The raw silk obtained is very thin, generally less than 10 microns thick. The carbon atoms in the raw material have a structure similar to graphite molecules and will change into a strong hexagonal structure during processing.

3. The “carbon fiber flower” blooming on the loom

The cloth-like texture and structure of carbon fiber determines that it cannot be easily formed, and forming is a necessary step in the preparation process. Typically, carbon fiber is “woven” into shape by a loom.

However, in addition to this textile molding method, there is also a mold molding method. Carbon fiber “cloth” usually has special textures and patterns, which lead to differences in the properties of the cloth itself. A particular fabric may have good tensile strength both horizontally and vertically, but be prone to deformation when placed diagonally. Different carbon fiber cloths will exhibit tensile properties in different axial directions, but there is always one direction in which the tensile strength is not high.

Of course, fully formed carbon fiber has great tensile strength in any direction. Usually, carbon fiber cloths with different textures are stacked together to form, so that the resulting product can achieve the expected compressive strength in all directions, making the entire carbon fiber appear very hard.

4. “Defects” of carbon fiber

Carbon fiber material also has a disadvantage, which is that it can be very brittle. Although carbon fiber is very strong, its lattice structure is more easily broken than steel and aluminum.

Why not make everything out of carbon fiber? It has a lot to do with cost. The preparation process of carbon fiber determines that it cannot be mass-produced like other chemical products. Its process is very complicated (including raw fiber preparation, sizing, and curing). In addition, the raw materials used in carbon fiber preparation are not cheap.

So, this is not a problem with carbon fiber materials. As long as you can afford the high cost, you can make anything you want with carbon fiber. For example, to buy a bicycle, as long as you are willing to pay 3 to 10 times more than an aluminum bicyclePrice, then you can certainly own a carbon fiber bike. Carbon fiber materials are very common in imported vehicles. Even some very affordable cars, such as the Chevrolet Corvette, also use carbon fiber materials. As long as you don’t care about the price, you can buy various carbon fiber components for your car. You can buy various carbon fiber daily necessities for yourself.

Especially in high-tech fields such as aerospace, carbon fiber is very cost-effective. The fan turbine blades of new Airbus and Boeing aircraft (Boeing 787 and Airbus A350) use a large amount of carbon fiber materials. The excellent performance of carbon fiber, its light weight and high strength, completely offset the drawback of high manufacturing cost. During the production process of the 787, Boeing found that carbon fiber materials generally do not have weld lines or cracks like metal materials. However, stress cracks were found in the wing panels of 42 aircraft waiting for delivery, and they had to be replaced. Rework, the reason showed that there was no filling gasket between the gaps, resulting in excessive stress. It seems that the application of new materials is also a very challenging task.