I News
Generally, absorbing materials can be divided into two categories: coating absorbing and structural absorbing. The application of carbon fiber in this regard belongs to structural absorbing. Ordinary carbon fiber is a reflector of electromagnetic waves and does not have absorbing properties. Only carbon fiber with special cross-section and carbon fiber composite materials with special structure have absorbing functions. When using carbon fiber as absorbing material, special attention should be paid to the following aspects: 1. Surface modified carbon fiber
A layer of porous carbon particles is deposited on the surface of carbon fiber or a layer of porous carbon microspheres is attached to improve its electromagnetic properties and give it certain absorbing properties.
2. Low-temperature carbonized carbon fiber
Low-temperature carbon fiber refers to carbonization temperature lower than normal carbonization temperature. Its purpose is to regulate resistance value. The higher the carbonization temperature, the smaller the resistance value and the worse the absorbing performance. However, low carbonization temperature affects the tensile strength and modulus of carbon fiber. Comprehensive consideration should be given to find the optimal carbonization temperature that takes into account resistivity, modulus and tensile strength.
3. Honeycomb structure
The carbon fiber ply in the carefully designed skin forms a certain angle with the incident wave, giving it a certain absorbing ability. Because the direction of the electric field is parallel to the fiber axis, the carbon fiber is a reflector of radar waves; when the direction of the electric field is perpendicular to the fiber axis or oblique to the fiber axis, the carbon fiber has a certain thinning function. At the same time, magnetic loss and electric loss absorbers, such as carbon powder and ferrite, are added to the foam plastics inside the honeycomb to make the incident radar waves reflect multiple times and convert them into heat energy and be absorbed. This structural absorbing material can be used to manufacture fuselages, wings, and noses.
4. Verify the shape and size of carbon fiber with special cross-sections
Adjust its shape and size to obtain the required resistance and surface resistivity. This research work has been carried out both at home and abroad. Taking the special-section carbon fiber developed by Toray Corporation of Japan as an example, the tensile strength of the obtained special-section carbon fiber can reach 4.43GPa, and the tensile modulus is 245GPa, which can be used to manufacture composite materials for absorbing and bearing.
5. Hybrid absorbing structure
The resistivity of the reinforcing fiber varies greatly. Carbon fiber is a good conductor, glass fiber is an insulator, and silicon carbide fiber is a semiconductor. According to the design parameters of the surface resistance, carbon fiber is mixed with glass fiber or carbon fiber is mixed with silicon carbide fiber in a certain proportion to give it a certain wave absorption performance. This type of wave absorption belongs to electrical loss, and magnetic loss is much stronger than electrical loss.
As a national strategic new material, carbon fiber is not only widely used in the field of aerospace, but also in other fields such as tank armor materials, marine ships, missile rocket weapons, etc. It is also a key strategic material for national defense and national economic construction. It is the material basis and technical guide for the development of national defense technology and the transformation of traditional industries in various countries. It is of great significance to actively develop technologies related to carbon fiber composite materials. At the same time, how to give carbon fiber magnetism will also be one of the research topics in the future.
A layer of porous carbon particles is deposited on the surface of carbon fiber or a layer of porous carbon microspheres is attached to improve its electromagnetic properties and give it certain absorbing properties.
2. Low-temperature carbonized carbon fiber
Low-temperature carbon fiber refers to carbonization temperature lower than normal carbonization temperature. Its purpose is to regulate resistance value. The higher the carbonization temperature, the smaller the resistance value and the worse the absorbing performance. However, low carbonization temperature affects the tensile strength and modulus of carbon fiber. Comprehensive consideration should be given to find the optimal carbonization temperature that takes into account resistivity, modulus and tensile strength.
3. Honeycomb structure
The carbon fiber ply in the carefully designed skin forms a certain angle with the incident wave, giving it a certain absorbing ability. Because the direction of the electric field is parallel to the fiber axis, the carbon fiber is a reflector of radar waves; when the direction of the electric field is perpendicular to the fiber axis or oblique to the fiber axis, the carbon fiber has a certain thinning function. At the same time, magnetic loss and electric loss absorbers, such as carbon powder and ferrite, are added to the foam plastics inside the honeycomb to make the incident radar waves reflect multiple times and convert them into heat energy and be absorbed. This structural absorbing material can be used to manufacture fuselages, wings, and noses.
4. Verify the shape and size of carbon fiber with special cross-sections
Adjust its shape and size to obtain the required resistance and surface resistivity. This research work has been carried out both at home and abroad. Taking the special-section carbon fiber developed by Toray Corporation of Japan as an example, the tensile strength of the obtained special-section carbon fiber can reach 4.43GPa, and the tensile modulus is 245GPa, which can be used to manufacture composite materials for absorbing and bearing.
5. Hybrid absorbing structure
The resistivity of the reinforcing fiber varies greatly. Carbon fiber is a good conductor, glass fiber is an insulator, and silicon carbide fiber is a semiconductor. According to the design parameters of the surface resistance, carbon fiber is mixed with glass fiber or carbon fiber is mixed with silicon carbide fiber in a certain proportion to give it a certain wave absorption performance. This type of wave absorption belongs to electrical loss, and magnetic loss is much stronger than electrical loss.
As a national strategic new material, carbon fiber is not only widely used in the field of aerospace, but also in other fields such as tank armor materials, marine ships, missile rocket weapons, etc. It is also a key strategic material for national defense and national economic construction. It is the material basis and technical guide for the development of national defense technology and the transformation of traditional industries in various countries. It is of great significance to actively develop technologies related to carbon fiber composite materials. At the same time, how to give carbon fiber magnetism will also be one of the research topics in the future.
