Strength of ceramic matrix-metal fibre composites

A failure model appropriate to ceramic matrix composites is described. The ultimate strain of the fibre is greater than that of the matrix. The contribution of interface phenomena to the effective surface energy of the composite is assumed to be zero: the interface just causes a crack in the matrix to stop and go around a fibre. Theoretical evaluation and experimental results obtained for composites with oxide matrices and molybdenum fibres show that microcracks in the matrix propagate in an unstable manner at low fibre volume fraction and in a stable manner at high fibre volume fraction. The strength of a ceramic matrix composite with a strong interface can in some cases be higher than that of the matrix.