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 C-ij of a silicon carbide fibre with transverse isotropy from room temperature up to 873 K. Firstly, we measured the C-ij 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 C-ij. Secondly, we applied a micromechanics calculation to deduce the fibre C-ij from the measured composite and matrix C-ij. The resulting fibre C-ij shows strong anisotropy in the temperature derivatives of the C-ij; the temperature derivatives for the fibre-axis-direction C-ij are much smaller than the others.