Effect of dynamic loading on tensile strength and failure mechanisms in a SiC fibre reinforced ceramic matrix composite

Abstract

The tensile strength and associated failure micromechanisms have been characterized for a SiC fibrereinforced ceramic matrix composite subject to strain rates approaching 1000 s⁻¹. It is found that behaviour under such conditions is not described by the current matrix fracture/fibre pull-out models. This is a consequence of the rapid and extreme frictional heating produced at the fibre-matrix interface by sliding velocities on the order of 100 ms⁻¹. At sufficiently rapid loading rates, the near-interface matrix appears to melt, and the frictional interface shear resistance is reduced to the point that the fibres debond throughout the specimen, and pull out without failing. This suggests that for sufficiently rapid loading, the stress to fail the composite will approach that merely to create the initial matrix crack, i.e., a stress level well below the ultimate strength normally attainable under quasi-static conditions.