Study On High Temperature Resistance And Tribology Properties Of 3D Carbon Fiber Felt/Portland Cement Composite

As a vehicle safety components,the performance of brake pads is very important in the car brake process.Therefore,the research of high-performance brake friction material is still the key matter which need to solve in the development of China’s vehicles.In view of the problem that heat resistance of the traditional resin-based brake friction material is poor,we change the matrix bonding material to improve heat resistance.In this paper,carbon fiber felt/Portland cement(CFF/PC)composites is prepared by using inorganic nonmetallic Portland cement as matrix adhesive and carbon fiber felt as internal reinforcement,silica fume,silicon carbide,graphite and so on as filler and modifier to study its high temperature performance and its internal composition changes at different temperatures,and the carbon fiber in the three-dimensional carbon felt is coated by the alumina sol to improve the high temperature resistance of the carbon felt and the composite material.On this basis,adding graphite,silicon carbide and other filler to the composite material to adjust the friction coefficient of friction and wear,and exploring the friction and wear properties of CFF/PC composites.The mechanical properties,friction and wear properties of the composites are tested by universal testing machine,friction tester,SEM scanning and XRD equipment.The research indicates:(1)The carbon fiber and cement matrix has a good mechanical bite and chemical bond bonding in the CFF/PC composite,carbon fiber has a good thermal conductivity and is threedimensional distribution in the cement matrix,The heat transfer of CFF/PC composite material is more quickly to the internal temperature uniformity through the carbon fiber at high temperatures,Thereby reducing the stress due to temperature gradients within the material,avoiding the high temperature burst phenomenon.Which improves the mechanical properties of the composites at high temperature.The flexural strength of CFF/PC at room temperature is 45 MPa and the compressive strength is 56 MPa.The flexural strength of pure cement is only about 15 MPa,and the compressive strength is 50 MPa.Flexural strength and compressive strength are increased by 200% and 12%,respectively.And there is still part of the carbon fiber existence in the composite material at 600℃ ablation 1h,It is suggest that the cement matrix has a protective effect on the carbon fiber,and the decomposition of the carbon fiber at high temperature is slowed down to ensure that the CFF/PC composites have certain mechanical properties at high temperature.(2)Preparation of different concentrations of alumina sol by sol-gel method,with the certain amount of alumina sol coating to the surface of carbon fiber.At a certain temperature,the phase transition occurs from AlOOH to Al2O3.After the carbon fibers are coated with different concentrations of alumina sol,the effect of different solubility of alumina on the coating effect is compared.It is found that impregnation of carbon felt with 0.3mol/L alumina sol is the best,which make CFF can withstand high temperature of 800℃.(3)When the alumina sol is coated onto the surface of the carbon fiber,alumina coating can increase the interface bonding properties between carbon fiber and cement matrix,which can improve the mechanical properties of composites.At the same time,because Al2O3 coat on the surface of carbon fiber,carbon fiber can effectively improve the high temperature oxidation resistance.Through testing,it is found that no coated carbon felt has been oxidized completely at 500℃ ablation 1h,while the carbon fiber felt after the coated has some remain at the temperature of 800℃,and the mechanical properties of the composites at high temperature have been improved.(4)The friction and wear properties of the composites are modified by graphite and SiC,The experimental results show that the friction coefficient of composite material decreases with the increase of graphite content,while the wear rate of composite material decreases first and then increases with the increase of graphite content.The friction coefficient of the composites increases only slightly with the increase of SiC content.The wear rate of the composites decreases with the increase of SiC content,but the variables are not large.We choose 12% graphite content of the composite material,and then add SiC to the composite material for friction coefficient and wear rate of the debugging.When the graphite content is 12% and the SiC content is 9%,the friction coefficient of the composites is about 0.4,and the wear rate is 1.7 x 10-7cm3/(N * m).