Advantages of traditional metal materials over new materials

Compared with metal materials, carbon fiber materials are light in weight and high in specific strength and stiffness. The following table gives a comparison of mechanical properties between cross-ply fiber composites and conventional materials. It can be seen that the traditional carbon steel performs very well in modulus and strength, but the high density seriously affects the lightweight application. The modulus and strength of 6 series aluminum are less than those of carbon steel, but the density is smaller. The modulus of resin-based carbon fiber is higher than that of aluminum alloy, and its strength can reach the level of high-strength steel through design, which is much higher than that of aluminum alloy, and its advantages in performance and lightweight are very obvious.

02 design

Metal materials are usually isotropic, yielding or conditionally yielding. However, single-layer carbon fiber has obvious directionality. The mechanical properties of the single-layer plate along the fiber direction are two orders of magnitude higher than those along the vertical fiber direction1~, and the stress-strain curve before fracture is linear elastic.

Therefore, carbon fiber materials can choose the laying angle, laying ratio and laying sequence of single layers through the laminated plate theory. According to the characteristics of load distribution, targeted design can achieve the required stiffness and strength performance, while traditional metal materials can only be achieved by thickening. At the same time, the performance cutting design of laminated plates can not only obtain the required in-plane stiffness and strength performance, but also obtain the unique coupling stiffness in-plane and out-of-plane

03 Corrosion resistance

Compared with metal materials, carbon fiber materials have strong acid and alkali corrosion resistance. Carbon fiber is a microcrystalline structure similar to graphite crystal formed by graphitization at high temperature of 2000-3000℃. This structure itself has high medium corrosion resistance, even in 50% hydrochloric acid, sulfuric acid or phosphoric acid, it can basically keep the elastic modulus, strength and diameter unchanged. Therefore, carbon fiber, as a reinforcing material, has sufficient guarantee in corrosion resistance, and different matrix resins have different corrosion resistance. Such as common carbon fiber reinforced epoxy resin, epoxy resin has good weather resistance and can still maintain its strength.

04 fatigue resistance

The main factors affecting the fatigue properties of carbon fiber composites are compressive strain and high strain level. Fatigue performance is usually tested by compression (R= 10) and tension-compression (R=- 1), while metal materials are generally tested by pulling (R=0. 1). Compared with metal parts, especially aluminum alloy, carbon fiber parts have excellent fatigue performance. Carbon fiber composites have better application advantages in areas with high fatigue resistance, such as automobile chassis. At the same time, carbon fiber materials have almost no notch effect. Most carbon fiber laminates have the same S-N curve in the whole life cycle, whether there is notch test or not.

05 recyclability

At present, the mature carbon fiber matrix adopts thermosetting resin, which is difficult to be extracted and reused after curing and crosslinking, and has a great impact on the environment. Therefore, the difficulty of carbon fiber recycling is one of the bottlenecks of industrial development, and it is also a technical problem that needs to be solved urgently in large-scale application. At present, most recycling methods at home and abroad are generally expensive and difficult to industrialize. Walter carbon fiber is actively exploring the solution of recyclable materials, and has completed the trial production of several samples, with good recycling effect and 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 recovery difficulty are still the bottlenecks restricting its further application. It is believed that with the breakthrough and innovation of technology and technology, the application of carbon fiber in automobiles will be more and more.