The difference between carbon fiber and metal.

Among many materials, carbon fiber composites (CFRP) have been paid more and more attention to for their excellent specific strength, specific stiffness, corrosion resistance, and fatigue resistance.

The different characteristics between carbon fiber composites and metal materials also provide engineers with different design ideas.

The following will be a simple comparison between carbon fiber composites and traditional metal characteristics and differences.

1. Specific stiffness and specific strength

Compared with metal materials, carbon fiber materials have lightweight, high specific strength, and specific stiffness. The modulus of resin-based carbon fiber is higher than that of aluminum alloy, and the strength of resin-based carbon fiber is much higher than that of aluminum alloy.

2. Designability

Metal materials are usually all the same sex, there is a yield or conditional yield phenomenon. And the single-layer carbon fiber has obvious directivity.

The mechanical properties along fiber direction are 1 ~ 2 orders of magnitude higher than those along vertical fiber direction and longitudinal and transverse shear properties, and the stress-strain curves are linear elastic before fracture.

Therefore, the carbon fiber material can select the laying angle, the laying ratio, and the laying sequence of the single-layer through the lamination plate theory. According to the characteristics of load distribution, the stiffness and strength performance can be obtained by design, while traditional metal materials can only be thickened.

At the same time, the required in-plane stiffness and strength as well as the unique in-plane and out-of-plane coupling stiffness can be obtained.

3. Corrosion resistance

Compared with metal materials, carbon fiber materials have strong acid and alkali resistance. Carbon fiber is a microcrystalline structure similar to graphite crystal formed by graphitization at a high temperature of 2000-3000 °C, which has high resistance to medium corrosion, in up to 50% hydrochloric acid, sulfuric acid or phosphoric acid, the elastic modulus, strength, and diameter remain basically unchanged.

Therefore, as a reinforcing material, carbon fiber has enough guarantee in corrosion resistance, different matrix resin in corrosion resistance is different.

Like the common carbon fiber-reinforced epoxy, the epoxy has better weather resistance and still maintains its strength well.

4. Anti Fatigue

The compression strain and high strain level are the main factors influencing the fatigue properties of carbon fiber composites. The fatigue properties are usually subjected to the fatigue tests under pressure (R = 10) and tensile pressure (r =-1), while the metallic materials are subjected to tensile fatigue tests under pressure (R = 0.1). Compared with metal parts, especially aluminum alloy parts, carbon fiber parts have excellent fatigue properties. In the field of automobile chassis and so on, carbon fiber composites have better application advantages. At the same time, there is almost no notch effect in carbon fiber. The S-N curve of the notched test is the same as that of the unnotched test in the whole life of most carbon fiber laminates.

5. Recoverability

At present, the mature carbon fiber matrix is made of thermosetting resin, which is difficult to be extracted and used again after curing and cross-linking. Therefore, the difficulty of carbon fiber recovery is one of the bottlenecks of industrial development, and also a technical problem that needs to be solved urgently for large-scale application. At present, most of the recycling methods at home and abroad have high costs and are difficult to be industrialized. Walter carbon fiber is actively exploring recyclable solutions, has completed a number of samples of trial production, recovery effect is good, with mass production conditions.

Conclusion

Compared with traditional metal materials, carbon fiber materials have unique advantages in mechanical properties, lightweight, designability, and fatigue resistance. However, its production efficiency and difficult recovery are still the bottlenecks of its further application. It is believed that carbon fiber will be used more and more along with the innovation of technology and process.


Post time: Jul-07-2021