Experimental investigation of vibration damping and the dynamic Young's modulus in MoSi2 and MoSi2-50Si3N4/SCS-6 at elevated temperatures

The effects of adding Si 3 N 4 and SiC fibers to MoSi 2 , forming MoSi 2 -50Si 3 N 4 /SCS-6, were studied at temperatures ranging from 21°C to 865°C. From the Archimedes method, the measured densities of two MoSi 2 samples and one composite were 6125 kg/ m 3 , 6113 kg/m 3 and 3705 kg/m 3 , respectively at room temperature. The Piezoelectric Ultrasonic Composite Oscillator Technique was employed to measure Young's modulus and damping properties. At room temperature, Young's modulus was 322 GPa and 399 GPa for the MoSi 2 samples and 235 GPa for the composite. Further mechanical damping values for MoSi 2 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 of -0.0148 GPa/°C.