Elastic-stiffness coefficients of a silicon carbide fibre at elevated temperatures: Acoustic spectroscopy and micromechanics modelling

We have determined all five independent elastic-stiffness coefficients Cij of a silicon carbide fibre with transverse isotropy from room temperature up to 873 K. Firstly, we measured the Cij of a titanium-alloy-matrix composite reinforced unidirectionally with the fibres and the matrix alloy alone. Electromagnetic acoustic resonance detected the free-vibration resonance frequencies of the specimens to determine their Cij . Secondly, we applied a micromechanics calculation to deduce the fibre Cij from the measured composite and matrix Cij . The resulting fibre Cij shows strong anisotropy in the temperature derivatives of the Cij ; the temperature derivatives for the fibre-axis-direction Cij are much smaller than the others.