Coupled effects of dispersions in interface sliding stress and fiber strength on tensile response of ceramic composites

Abstract

Micromechanics models for fiber-reinforced ceramic composites consider fiber strength as stochastic but assume other material properties are deterministic. However, experimental data show considerable variability in interface sliding stress within single composite specimens. This study advances the models by integrating sliding stress dispersions with stochastic fiber strength. We use analytical models and Monte Carlo simulations to investigate the combined effects of these dispersions in two scenarios: (i) a composite containing a single matrix crack bridged by fibers, where the matrix is rigid and cannot crack away from the main crack, and (ii) a composite with a single fragmenting fiber in a matrix that is heavily-cracked, unable to bear axial load but rigid in shear. Results show that dispersion effects in the first case lead to greater strength reductions than in the second. Dispersion effects are attributed to differences in characteristic fiber strengths, uniformity of fiber loading, and fractional lengths of slipped fibers. Analytical formulations describing the combined dispersion effects are also developed and evaluated. Finally, examination of the results reveals a deficiency in the single fiber composite model, highlighting a flaw due to the absence of kinematic constraints on fiber extension across matrix cracks.