Dynamic elastic moduli and mechanical damping were measured with the PUCOT (piezoelectric ultrasonic composite oscillator) technique at room temperature for ceramic-matrix composites (CMCs) of the following compositions: PRD-166 (fibres)/N51A glass (matrix), PRD-166 fibres coated with SnO2/glass, Nextel 480 fibres/glass, Nextel 480 fibres coated with SnO2/glass, and Nextel 480 fibres coated with BN/glass. The fibres were continuous, and the volume fractions varied from 0.24 to 0.43. Some of the mechanical-property measurements correlated with the thickness of one of the coating materials, and with microstructural observations of the misorientation angle of the fibres and normalized fibre length. With increasing volume fractions of fibres, the fraction of broken fibres increased. For the PRD-166/glass and PRD-166/SnO2/glass, a substantial fraction of the fibres were misoriented by angles of up to 15 °. Assessments were made of the measured properties in terms of the rule of mixtures and other theoretical estimations.
Microstructure Elastic Modulus Mass Density Coating Material Fibre Length
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