The Research On The Tribological Properties Of Rare Earth Solution Treated Carbon Fiber Reinforced Thermoplastic Polyimide Composites

Thermoplastic resin matrix composite is not only corrosion resistance, non-toxic, but also can be used to process repeatedly, is beneficial to the environment and thus attracted a great deal of attention. Thermoplastic polyimide (PI) with outstanding thermal stability, good impact resistance, solvent resistance and anti-radiation is a potential matrix material applied to the field of tribology. Carbon fiber with high temperature, high-intensity, high elastic modulus, creep resistance characteristics such as it is the most commonly used as reinforcing fiber to high-performance resin matrix composite materials. However, without surface treatment, the carbon fiber surface area activity is small and the surface energy is low. Being used for the reinforcement of composite materials, the property of carbon fiber can not be fully exerted for its poor adhesion with resin, thus the interfacial bonding has become more important.According to the surface properties of carbon fiber and the unique physical and chemical characteristics of rare earth, rare earth solution (RES) surface modification method was used for the surface modification of carbon fiber to improve the interfacial bonding of carbon fiber/polyimide (CF/PI) composite, effectively improving the mechanical properties and tribological properties of CF/PI composite.Firstly, RES method and air-oxidation method are used to modify caibon fiber, and CF/PI composite with different interface are prepared. The effects of surface modification on CF/PI composites were evaluated through mechanical property tests. Results show that both RES treatment and air-oxidation method can increase the interfacial properties of CF/PI composite, and RES treatment is much more effective.Secondly, XPS was used to characterize the carbon fiber before and after treatment. Both RES method and air-oxidation method can increase the surface activity of carbon fiber. Air-oxidation method will etch the carbon fiber surface, affecting the mechanical properties of carbon fiber. Rare earth element will coordinate with atom C, O, N on carbon fiber surface and organic functional groups in RES. Thus the activity groups on carbon fiber increase and rare earth element can continue to coordinate with oxygen containing functional groups on PI. And strong and tough structure is formed in the composite interface, so the interfacial property of CF/PI composite is improved.Thirdly, reciprocating tribological test is conducted to study the friction and wear properties of CF/PI composite with different carbon fiber content. Results show that filling in the polyimide with carbon fiber can effectively improve the tribological properties of CF/PI composite. At the same friction conditions, 20vol%, CF/PI composite has the lowest coefficient of friction and wear; With the increase of load and reciprocating sliding frequency, the friction coefficient and wear of CF/PI composite increase.Fourthly, the tribological mechanism of CF/PI composite with different interface is further studied. The effects of reciprocating sliding frequency, load and lubricating condition on tribological property were analyzed. Results show that effects of load and reciprocating sliding frequency on the tribological mechanism of CF/PI composite with different interface are different. With the increase of load and reciprocating sliding frequency, interfacial properties affect the physical characteristics of friction contact surface greatly. The tribological properties of untreated and air-oxidated CF/PI composite are greatly affected by load and reciprocating sliding frequency. While the tribological properties of RES treated CF/PI composite change little with load and reciprocating sliding frequency. In the same test conditions, the friction and wear properties of the RES treated CF/PI composite are optimal; Under oil lubrication, the tribological properties of CF/PI composite is better than that in dry sliding condition due to lubrication, cooling and hydrodynamic effect.RES modification method was used to modify the carbon fiber. The mechanism of RES treatment on carbon fiber is analyzed. The relationship between surface modification method and mechanical properties of CF/PI composite were discussed. And the tribological law of CF/PI composite is further studied. The application of the RES modification method in the field of surface engineering is developed. Composite interface theory and tribological theory are combined to prompt the development of tribological area.