Carbon fiber composite
The carbon fiber reinforced resin matrix composite is a new type of material, which is made of organic polymer material as the matrix and carbon fiber as the reinforcement through the composite process, and has significantly better performance than the original component. ". It has become one of the most important aviation structural materials due to its high specific strength, high specific modulus, fatigue resistance, corrosion resistance, strong design integrity, convenience for large area integral molding, and special electromagnetic properties.
The matrix resins used in carbon fiber reinforced resin matrix composites are mainly divided into two categories: thermosetting resin and thermoplastic resin. The thermosetting resin is composed of reactive low molecular weight prepolymer or high molecular weight polymer with active group. During the molding process, it is cross-linked and condensed under the action of curing agent or heat to form an insoluble cross-linked structure. Commonly used are epoxy resin, phenolic resin, bismaleic phthalein amine resin, etc. Thermoplastic resin is composed of linear high molecular weight polymer, which is dissolved and melted under certain conditions, and only physical changes occur. Commonly used are polyethylene, nylon, PEEK, etc.
Common carbon fiber materials:
1. Carbon fiber reinforced ceramic matrix composites
Ceramics have excellent corrosion resistance, wear resistance, high temperature resistance and chemical stability, and are widely used in industrial and civil products. However, its fatal weakness is its brittleness, and it is very sensitive to subtle defects such as cracks, pores and inclusions. Carbon fiber reinforced ceramics can effectively improve the toughness, change the brittle fracture morphology of ceramics, and prevent the rapid propagation and propagation of cracks in ceramic matrix. At present, the relatively mature carbon fiber reinforced ceramic material at home and abroad is carbon fiber reinforced silicon carbide material. Because of its excellent high temperature mechanical properties, it does not need additional thermal insulation measures to serve at high temperatures, so it is widely used in aeroengines, reusable aerospace vehicles and other fields.
2. Carbon/carbon composites
Carbon/carbon composite is the abbreviation of carbon fiber reinforced carbon matrix composite, and it is also a kind of advanced composite. It is composed of carbon fiber, fabric, woven fabric and other reinforced carbon matrix composites. Carbon/carbon composites are mainly composed of various types of carbon, namely fiber carbon, resin carbon and deposited carbon. This kind of composite, which is composed of pure carbon elements completely designed and manufactured artificially, has many excellent properties. In addition to high strength, high rigidity, dimensional stability, oxidation resistance and wear resistance, it also has high fracture toughness and pseudoplasticity. Especially in high temperature environment, it has high strength, no melting, no burning, and only uniform ablation, which is incomparable to any metal material. Therefore, it is widely used in high-tech fields such as missile warheads, solid rocket motor nozzles and aircraft brake discs.
3. Carbon fiber reinforced metal matrix composites
Carbon fiber reinforced metal matrix composite is a composite material with carbon fiber as the reinforcement fiber and metal as the matrix. Compared with metal materials, carbon fiber reinforced metal matrix composites have higher specific strength and specific modulus; Compared with ceramics, it has high toughness and impact resistance. Aluminum, magnesium, nickel, titanium and their alloys are mostly used as metal matrix. Among them, the preparation technology of carbon fiber reinforced aluminum and magnesium composites is relatively mature. The main technical difficulty in manufacturing carbon fiber reinforced metal matrix composites is the surface coating of carbon fibers, so as to prevent damage to carbon fibers during the process of compounding, thus reducing the overall performance of the composites. At present, the surface modification of carbon fibers mainly adopts vapor deposition, liquid sodium method, etc. when preparing carbon fiber reinforced metal matrix composites, but its complex process and high cost limit the promotion and application of carbon fiber reinforced metal matrix composites.
4. Carbon fiber reinforced cement based composite
Carbon fiber reinforced cement composites (CFRC) are made by adding carbon fiber into the cement matrix, which is called fiber reinforced concrete. Adding high-strength carbon fiber into cement-based materials is an important measure to improve the crack resistance, impermeability, shear strength and elastic modulus of cement composites, control crack propagation, improve strong alkali resistance and enhance deformation capacity.
In addition, the carbon fiber also has the vibration damping property, which can absorb the vibration wave and improve the seismic resistance and bending strength by more than ten times. What is more valuable is that carbon fiber has conductivity. Adding it to the cement matrix endows the cement matrix with intelligence, which greatly expands the application scope of concrete.
The surface of CFRC composite will not crack under load. Its tensile strength, bending strength and fracture toughness are several to ten times higher than those without reinforcement, and its impact toughness is also considerable. The length of carbon fiber used for chopped carbon fiber reinforced cement is generally 3-6 nm, and the diameter is 7-20 μ m. The tensile strength ranges from 0.5 to 0.8 GPa. The strength of ordinary cement is generally 11.76MPa. If 15% carbon fiber is added by weight, the strength can reach 245MPa; If the amount of admixture is 20%, the strength can reach 548.8MPa.
In addition, compared with ordinary concrete, CFRC has the advantages of light weight, high strength, good fluidity, strong diffusion, and high surface quality after forming. When it is used as a partition, it is 1/2~1/3 thinner than the partition made of ordinary concrete, and its weight is 1/2~1/3 lighter. CFRC has a variety of specifications, among which short cut carbon fiber reinforced concrete is mainly used in roof, exterior wall, interior wall, ground, ceiling, etc; Long fiber concrete is used in load-bearing components. The components made of it have stable dimensions, and also have anti-static, wear resistance, corrosion resistance and other properties. Therefore, the research on the performance of CFRC has developed rapidly in recent years.
source:https://mp.weixin.qq.com/s/Y5MDhISUCvmcr5guRRpJSg