Experimental investigation of vibration damping and the dynamic Young's modulus in MoSi2 and MoSi2-50Si(3)N(4)/SCS-6 at elevated temperatures

The effects of adding Si3N4 and SiC fibers to MoSi2 forming MoSi2-50Si(3)N( 4)/SCS-6, were studied at temperatures ranging from 21 degrees C to 865 deg rees C. From the Archimedes method, the measured densities of two MoSi2 sam ples and one composite were 6125 kg/m(3), 6113 kg/m(3) and 3705 kg/m(3) res pectively at roam temperature. The Piezoelectric Ultrasonic Composite Oscil lator Technique It ns employed to measure Young's modulus and damping prope rties. At roam temperature, Young's modulus was 322 GPa and 399 GPa for the MoSi2 samples and 235 GPa for the composite. Further mechanical damping va lues for MoSi2 and the composite were found to be near 3x10(-3) and 6x10(-3 ), respectively and independent of the strain amplitude at room temperature . Young's modulus of the composite was found to change linearly at a rate o f -0.0148 GPa/degrees C.