A Study On The Dynamic Compressive Mechanical Properties Of C/SiC Composites

Fiber reinforced ceramic matrix composites C/SiC keep the ceramic materials merits which are heat-resistant, low density, high ratio of stiffness/weight, oxidation-resistant, erode-resistant et al. And the defect of large brittleness is overcomed by the fiber increasing the strength and toughness. It can be used in the combustion chamber of the aerial engine, the whole turbine, guided vane, exhaust nozzle, combustion chamber and nozzle in the rocket motors and so on. It could enhance the ratio of thrust/weight largely, and have an extensively applied future.The static and dynamic mechanical properties in room temperature of 2D-C/SiC and quasi-three dimensional C/SiC composites were investigated by using the electronic universal testing machine and the SHPB system. The Weibull distributions of the dynamic failure strengths were analyzed. And the rupture surface were observed by using an optical microscope and SEM. Results show that, the mechanical properties of the 2D- C/SiC and quasi-three dimensional C/SiC composites are rate-dependent, namely, the failure strength raises and the failure strain reduces with the strain rate increasing. But it is not quite sensitive. The dynamic failure strengths of the composites submit to the Weibull distribution. And the Weibull moduli are 8.36, 5.27 and 8.19. The larger damage angle is found for the high densification samples, and it is large under dynamic loading. Shear failure and delaminate failure are found on the quasi-three dimensional C/SiC samples under static loading, while split failure under dynamic loading. From the SEM, more cracked fibers are observed under high strain rate.Based on the experimental data, a new constitutive equation that includes the rate-dependent and damage-softening effects is proposed and it agrees with the experimental results very well.Otherwise, the static and dynamic mechanical properties in temperature of 200℃, 400℃ and 600℃ were investigated. And the relationships between the failure strength and strain rate and temperature were analyzed. Results show that, the failure strengths of the two kinds of densification 2D-C/SiC samples under different temperature increase with the strain rate increasing. Under the same strain rate loading, the failure strengths of the high densification 2D-C/SiC samples reduce with the temperature increasing with different temperature; the failure strengths of the low...