Study On Preparation And Performance Of GSI SiC/SiC Composites

SiC/SiC have high specific strength,high specific modulus,high temperature resistance,radiation resistance and other excellent properties,and have very broad application prospects in aerospace,nuclear field.Compared with the other composite materials preparation process,the advantages of GSI are the short preparation cycle,lower cost,lower residual porosity and so on.In this paper,the SiC/SiC composites fabricated by GSI process and their properties were studied.The effects of the factors such as the carbon content of the cracked layer,the interface modified coating and the type of preformed tire on the properties of SiC/SiC composites were studied.The effect of carbon content of SiC/C intermediates on the properties of SiC/SiC composites was studied by using 14.7% SiC fiber mat(T700 fiber as net tire)as reinforcements.With the increase of the carbon content,the flexural strength and modulus of the composites increase.For the preform with no interfacial coating,the carbon content of SiC/C intermediates obtained from four PIP cycles was moderate.The SiC/SiC composites prepared by GSI have the best flexural strength and modulus of 72.8MPa and 56.5GPa,respectively.The effect of CVD C interface modified coating on the properties of SiC/SiC composites was studied.Among them,SiC/SiC composites with the thickness of 0.77?m have higher performance.The SiC/SiC compositeswith the thickness of 0.77?m and the flexural strength are 95.6MPa and 57.4GPa,respectively.The effect of CVD SiC interface modified coating on the properties of SiC/SiC composites was studied.Among them,SiC/SiC composites with the thickness of 0.77?m have higher performance.The flexural strength and modulus of SiC/SiC composites increase first and then decrease with the increase of SiC coating thickness.When SiC interface coating thickness is 1.53?m,the flexural strength and modulus of SiC/SiC composites are the highest.The flexural strength and modulus of the composites were 114.4MPa and 122.5GPa,respectively.The effects of C,SiC bilayer interface coatings on the properties of SiC/SiC composites were investigated.A certain thickness of the two-layer interface coating helps to transfer the load interface,and protect the fiber from damage.When the inner carbon coating thickness is about 0.45?m and the outer SiC coating thickness is about 2.26?m,the flexural strength and modulus of SiC/SiC composites are the highest,107.7MPa and 82.1GPa,respectively.Compared with the single-layer CVD C-coated composite,the performance is significantly improved.SiC fiber mat(pre-oxidized PCS precursor fibers were netted)with 19.3% volume fraction were used as reinforcements.The SiC/SiC composites were prepared by GSI process and its properties were studied.SiC composites prepared by four cycles of PIP had the highest strength and modulus of 147.0MPa and 93 GPa.Compared with the fiber preforms with 14.2% volume fraction,the strength and modulus of the fiber preforms were increased by 102% and 64.6%,respectively.