Research On Preparation And Properties Of C/SiC Composites By Hot Press Sintering

As the new thermal protection material,C/SiC composites played an important role in the aerospace technology.At present,the preparation process of C/SiC composites are complex and long cycle.So the current problem is how to achieve the production rapidly.In the paper,the feasibility of rapid preparation of C/SiC composites by hot pressing sintering was discussed using T300 carbon fiber,SiC powder,phenolic resin as the starting materials.The effects of sintering temperature,hot pressing pressure and carbon fiber addition on mechanical properties,ablation resistance and thermal shock resistance of C/SiC composites are investigated systematically.The relative mechanisms were discussed as well.The results show that the density of C/SiC composites increased with the increasing of the sintering temperature and hot pressing pressure but decreased gradually with the increasing of the carbon fiber content.The content of the carbon fiber has the greatest influence on the density of the composites.The composite with the maximum density of 2.55g·cm^-3is obtained when the sintering temperature is2100?,the hot pressing pressure is 30 MPa and the carbon fiber content was 35%.With the sintering temperature,hot-pressed pressure and carbon fiber content increasing,the bending strength of C/SiC composites increased gradually.The sintering temperature has the greatest influence on the flexural strength of the composites.When the sintering temperature was 2100?,the hot pressed pressure is30 MPa and the content of carbon fiber is 35%,the prepared C/SiC composites had the maximum bending strength(81.02 MPa).With the sintering temperature,hot pressing pressure and carbon fiber content increasing,the fracture toughness of C/SiC composites increased firstly and then decreased.The hot-pressed pressure has the greatest influence on the fracture toughness.When the sintering temperature is 2050?,the hot-pressed pressure was25MPa and the carbon fiber content is 30%,the C/SiC composites were obtained with the maximum fracture toughness of 3.62 MPa·m^-1/2.With the increasing of the hot-pressed pressure and carbon fiber content,the ablation resistance of C/SiC composites decreased gradually.With the increasing of the sintering temperature,the ablation resistance of C/SiC composites increased firstly and then decreased.The sintering temperature has the greatest influence on the ablation resistance of the composites.When the sintering temperature is 2050?,the hot-pressed pressure is 20 MPa and the carbon fiber content was 25%,the prepared C/SiC exhibited the best ablation resistance.The mass ablation rate of the sample is2.0mg/s in the acetylene flame of 1200?.With the increasing of the hot-pressed pressure,the thermal shock resistance of C/SiC composites decreased.With the increasing of the carbon fiber content,the thermal shock resistance of C/SiC composites increased gradually,while with the increasing of the sintering temperature,the thermal shock resistance of the composites decreased first and then increased.When the sintering temperature is 2000?and the hot pressing pressure is 20 MPa,the carbon fiber content is 35%,the obtained C/SiC composites exhibited the best thermal shock resistance.The optimized process parameters are the carbon fiber content of 30%,hot-pressed pressure of 25MPa and sintering temperature of 2050?.The C/SiC composites is obtained with the density of 84.5%,bending strength of 63.80MPa,fracture toughness of 3.62MPa·m^-1/2,mass ablation rate of 2.41mg·s^-1,and strength retention rate of 84.7%after thermal shock.