| With the rapid development of the economy,people's requirements for the speed of vehicles are getting higher and higher,and the corresponding requirements for the safety of the brake system are also higher.Therefore,a friction performance is stable,and the heat decay resistance is excellent.Long friction materials are necessary.At the same time,in today's increasingly serious environmental problems,how to prepare new materials that are environmentally friendly and pollution-free has also become a top priority.In order to develop a new type of green and high temperature resistant friction material,this thesis researches the application of Ground Granulated Blast-furnace Slag?GGBFS?as raw material,water glass?Na2SiO3?and potassium hydroxide as alkali activators,carbon fiber?CF?was used as toughening material,graphite as friction modifier to prepare Short-cut carbon fiber reinforced geopolymer composite friction material and investigates their friction properties.The main research contents include.Firstly,GGBFS is adopted as raw material,and different modulus of potassium water glass are used as activators to prepare geopolymer materials.The test specimens were tested by universal testing machine,XRD,SEM and other means to explore the influence of different potassium water glass modulus and different curing temperature on its performance.Using geopolymer as matrix,and the chopped carbon fiber as toughening phase,composite preparation of geopolymer composites.And the test specimens were tested by universal testing machine,XRD,SEM and other means to study the effect of chopped carbon fiber content on its performance.Short-cut carbon fiber toughened geopolymer composite friction material was prepared by adding graphite as a friction modifier to the composite.Finally,the mechanical properties,high temperature resistance and friction properties of geopolymer composite friction materials were investigated by universal testing machine,XRD,SEM,friction testing machine and TG.The results are as follows.?1?The influence of the modulus of potassium water glass on the compressive strength of geopolymer materials is first increased and then decreased.When the modulus of potassium glass is 1.9 M,the maximum strength is 115.68 MPa;Curing temperature also affects the strength of geopolymers.When the temperature is 60°C,the maximum strength is 130.90MPa.If the temperature is too high,the material is prone to cracks.?2?The addition of carbon fiber can significantly improve the toughness of geopolymer materials.The maximum strength is obtained when the volume fraction is 2.5%,and the compressive strength and flexural strength are 120.35 MPa and 50.91 MPa respectively.Excessive fiber content tends to cause defects in the matrix and lead to a decrease in strength.?3?The high temperature resistance test of geopolymer composite friction material was carried out at 200°C900°C,and compared with the mechanical properties at room temperature.The samples calcined within 600°C showed no obvious defects.After 700°C,the surface of the material began to show obvious cracks,and the color of the sample began to become lighter.During the calcination process,the overall strength of the sample decreased slightly,and no cracking occurred during the test,and the high temperature resistance was good.?4?The strength of the composite friction material is decreased after the addition of graphite.When the graphite content was 12%,the compressive strength and flexural strength were 95.91 MPa and 26.75 MPa,respectively.With the increase of graphite content,the friction coefficient of composites are decreases,and the wear rate is first decreases and then increases.When the graphite content is 9%,it has good friction performance,and its average friction coefficient is 0.42,the wear rate is 0.54×10-77 cm3/N·m,and the friction performance at room temperature,100°C,200°C and 300°C is relatively stable,which is in line with the national standard for brake linings for automobiles. |
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