| Wave-transparent materials which have been extensive used in aerospace field requires excellent performance because of their special occasion. The use of traditional resins such as phenolic and epoxy as wave-transparent materials is limited, because their mechanical properties decreased severely as the temperature increased. However, organic silicone resin, whose heat resistance and dielectric properties are excellent have attracted much attention. In Russia, this resin has been used successfully in the tactical missile and space shuttles as the matrix of composites. It has been shown that, the Boron element added in silicone resin, forming Si-O-B bridge can improve its heat resistance further.The SiBOCH silicone resin can be prepared by the chemical reaction of B(OH)3 and poly-methyl ethoxy siloxane (PMES). The FT-IR analysis showed that the B element has been successfully connected to the silicon-oxygen alkane structure as Si-O-B bond. Meanwhile , its thermal properties has also been analyzed by TG.This paper is to seek an optimal preparation method of the composites with this prepared silicone resin as matrix and quartz fiber (cloth) who has good dielectric properties as reinforcement. The mechanical properties and microstructures were analyzed by three point method, SEM, FT-IR and TG-DTA.In the research of fiber cloth reinforce silicone resin composites, it shows that, the removal of the fiber sizing has a significant effect on the flexural strength of composites. Coupling agent used in the interface between fiber and matrix to form a chemical combination, can improve mechanical properties more effectively than method of heat treatment and acid etching, which are physical treatment. In addition, the coupling agent KH550 is more appropriate than KH560. With the increase of temperature, water and ethanol in the composites volatilize, the cleavage of Si-C bond can generate CO2 and H2O , Si-O bond break and small molecule ring body were produced, all of these lead to a greater weight loss and a drop of the flexural properties , especially after 350℃. When the resin content of the composite is 40% (mass fraction), the resin matrix can cover the fiber better, so at room temperature its flexural strength can be 1.36 and 2.21 times higher than the content is 20% and 60% respectively. Ultrasonic vibration can promote the cleavage of Si-O-Si bond in silicone resin, which results in the flexural strength decrease. Among the several methods of fabrication, soaking-reaction mothd can perform better than vacuum-assisted impregnation and prepreg one. However the linear density of the fiber is relatively large, affecting the impregnation of resin glue. As a result, the improvement of strength is limited.Use unidirectional quartz fiber to fabricate composites by filament winding process, the flexural strength at room temperature can be 2.08 times as high as fiber cloth reinforced composites. The hot-pressing way used in the curing step, can improve the crosslinking effectively, lower the porosity of the material, reducing deformation. Consequently, the flexural strength of the composite is superior to pressureless way. At room temperature, it is 248.0 MPa on average, with a peak of 259.9MPa, which can be 0.526 times higher than the pressureless one. At 350℃, the flexural strength is 142.4Mpa, this can also be 0.584 times higher than the latter. |
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