Correlation of elastic properties of melt infiltrated SiC/SiC composites to in situ properties of constituent phases

The ability to correlate the elastic properties of melt infiltrated SiC/SiC composites to properties of constituent phases using a hybrid Finite Element approach is examined and the influence of material internal features, such as the fabric architecture and intra-tow voids, on such correlation is elucidated. Tensile testing was carried out in air at room temperature and 1204 °C. Through-thickness compressive elastic modulus utilizing the stacked disk method was measured at room temperature. In situ moduli of constituent materials were experimentally evaluated using nano-indentation techniques at room temperature. A consistent relationship is observed between constituent properties and composite properties for in-plane normal and shear moduli and Poisson’s ratio at room temperature. However, experimental data for through-thickness compressive elastic modulus is lower than the calculated value. It is hypothesized that the existence of voids inside the fiber tows and their collapse under compressive loads is the cause of such discrepancy. Estimates for the change in elastic moduli of constituent phases with temperature were obtained from literature and used to calculate the elastic properties of the composites at 1204 °C. A reasonable correlation between the in-plane elastic moduli of the composite and the in situ elastic properties of constituent phases is observed.