With the continuous development of the new energy vehicle industry, the requirements for lightweight vehicles are increasing day by day. Among many materials, carbon fiber composite materials are increasingly valued by people for their excellent specific strength, specific stiffness, corrosion resistance and fatigue resistance. The different characteristics between carbon fiber materials and metal materials also provide engineering designers with different design ideas. The following will briefly compare the characteristics and differences between carbon fiber composite materials and traditional metals.
01 Specific stiffness and specific strength
Compared with metal materials, carbon fiber materials are light in weight, high in specific strength and specific rigidity. The following table gives a comparison of the mechanical properties of Cross-Ply fiber composites and conventional materials. It can be seen that the traditional carbon steel performs very well in terms of modulus and strength, but the large density seriously affects lightweight applications. The modulus and strength of 6-series aluminum is less than carbon steel, but its density is small. The modulus of the resin-based carbon fiber is higher than that of the aluminum alloy, and the strength can reach the level of high-strength steel by design, which is much higher than that of the aluminum alloy. The advantages in both performance and light weight are very obvious.
02 Designability
Metal materials are usually isotropic, with yielding or conditional yielding. The single-layer carbon fiber has obvious directionality. The mechanical properties of the single-layer board in the fiber direction are higher than those in the vertical fiber direction and the vertical and horizontal shear properties by 1 to 2 orders of magnitude, and the stress-strain curve shows a linear elastic relationship before breaking.
Therefore, the carbon fiber material can choose the laying angle, the laying ratio, and the laying order of the single layer through the plywood theory. According to the characteristics of load distribution, targeted design can be used to obtain the required rigidity and strength performance, while traditional metal materials can only be achieved by thickening. At the same time, the performance cut design of laminates can not only obtain the required in-plane stiffness and strength performance, but also obtain the unique coupling stiffness between in-plane and out-of-plane.
03 Corrosion resistance
Compared with metal materials, carbon fiber materials have a strong ability to resist acid and alkali corrosion. Carbon fiber is a graphite-like microcrystalline structure formed by graphitization at a high temperature of 2000-3000 ° C. This structure itself has a high resistance to medium corrosion and can also be elastic in up to 50% hydrochloric acid, sulfuric acid or phosphoric acid. Modulus, strength and diameter remained basically unchanged. Therefore, as a reinforcing material, carbon fiber has sufficient guarantee in corrosion resistance, and different matrix resins have different corrosion resistance. Like the common carbon fiber reinforced epoxy resin base, the weather resistance of the epoxy resin is better, and the strength can still be maintained better.
04 Fatigue resistance
The main influencing factors of the fatigue characteristics of carbon fiber composite materials are compressive strain and high strain level. Fatigue performance is usually carried out in compression-compression (R = 10) and tension-compression (R = -1) fatigue tests, while metal materials are generally subjected to R = 0.1 tensile-tension fatigue tests. Compared with metal parts, especially aluminum alloy, carbon fiber parts have excellent fatigue performance. Carbon fiber composite materials have better application advantages in areas with high fatigue resistance requirements such as automobile chassis. At the same time, the carbon fiber material has almost no notch effect. Most carbon fiber laminates have the same S-N curve with the notch test and the S-N curve without the notch test over the entire lifetime.
05 Recyclability
At present, the mature carbon fiber matrix uses thermosetting resin, which is difficult to extract and use again after curing and crosslinking, which has a great impact on the environment. Therefore, the difficulty of recycling carbon fiber is one of the bottlenecks in industrial development, and it is also a technical problem that needs to be solved urgently for large-scale applications. At present, most recycling methods at home and abroad are generally costly and difficult to industrialize. Huate Carbon Fiber is actively exploring solutions for recyclable materials. It has completed trial production of multiple samples, with good recycling results and mass production conditions.
In conclusion
Compared with traditional metal materials, carbon fiber materials have unique advantages in mechanical properties, light weight, designability, and fatigue resistance, but their production efficiency and difficulty in recycling are still the bottlenecks restricting their further application. I believe that with the breakthroughs in technology and process, carbon fiber will be able to achieve more and more applications in automobiles.