Research On Grinding Mechanism And Quality Control Of 2.5D Carbon Fiber Reinforced Silicon Carbide Ceramic Matrix Composite(C_f/SiC)

Ceramic materials can still be used in a variety of harsh environments due to their high hardness and low density.but the sensitivity to cracks severely limits their applications.Carbon fiber reinforced ceramic matrix composites combine the excellent properties of carbon fiber and silicon carbide and are widely used in modern industries such as aerospace and braking systems.Due to the high cost of preparation and the characteristic of difficult processing,the materials are mostly manufactured by near net shape to reduce the processing allowance.But to meet the requirement of use,subsequent processing is indispensable.Grinding is cost-effective and the most important and efficient processing method for this type of composite material.The woven structure of the material determines its cost and performance.Compared with 1D,2D and 3D,2.5D needle punched structure has low production cost and has the advantages of similar three-dimensional structure.Many scholars have conducted related research on ceramic materials,1D and 2D ceramic matrix composite materials,but there are few studies on the grinding of 2.5D Cf/SiC needle punched composite materials and the effect of cooling and lubrication under different lubrication conditions has not been proved yet.Because of the strong anisotropy and heterogeneity of the material,different processing planes and fiber angles have a significant impact on the processing quality and removal mechanism.In summary,conduct grinding experiments on 2.5D Cf/SiC needle punched composite materials and SiC ceramics with grinding parameters,three processing planes,multiple fiber angles,and different lubrication methods as variables to investigate the role of the grinding force,Surface quality(surface roughness,surface morphology,and sub-surface damage),debris shape and grinding temperature,and clarify the grinding mechanism.The main research contents are:(1)Analyze the influence degree and the action law of the processing parameters,the different fiber angles of the three processing planes on the grinding force and surface roughness,obtain the processing plan of the minimum grinding force and surface roughness,and explore the relationship between the two indicators and the maximum undeformed chip thickness.The difference in grinding force between SiC ceramics and needle-punched composites is compared,and the surface quality of needle-punched composites under different lubrication conditions is quantitatively characterized by surface roughness.(2)Observe typical damage characteristics such as matrix cracks,interface debonding,fiber fracture and outcropping,analyze the influence of processing parameters,lubrication state and angle on the surface morphology.observe the surface quality after processing more intuitively and find the evolution of the surface morphology,the trend is consistent with the roughness.Comparing the sub-surface morphology characteristics of the typical positions of the three processing planes,it is found that the degree of damage is like the surface morphology.the difference in the bonding force of the materials at different positions causes the thickness of the sub-surface damage layer to be different.And observe the sub-surface morphology of typical damage characteristics at different grinding depths.The difference in the morphology of wear debris between SiC ceramics and needle punched composites is compared,the wear debris morphology of different grinding depths at three typical locations is observed,and the surface quality is analyzed from the microstructure level.Three positional relationship models are established to facilitate the analysis of the failure process of fiber and matrix.The toughening form of the needle-punched composite material is analyzed,and the grinding mechanism of three positional relationship between fiber and abrasive grains is explained in combination with the fracture characteristics of the brittle material.(3)The thermal imager is used to capture the grinding temperature of the needled composite material in different lubrication states under orthogonal and parallel planes to study the influence of different processing planes and lubrication states on temperature.The grinding temperature of SiC ceramic and needle-punched composite material is detected more accurately by thermocouple to explore the difference in grinding temperature of the two materials,and the action law of processing parameters on temperature is analyzed.