Analyses of fibre push-out test based on the fracture mechanics approach

Abstract

Theoretical analyses based on the concept of fracture mechanics have been developed to evaluate the interfacial properties of ceramic matrix composites in single fibre push-out tests. Two different fibre push-out models, i.e. single fibre-matrix model and three-cylinder model, were presented for different specimen geometries. The interfacial debonding and fibre push-out stresses were analyzed similar to the fibre pull-out test ( Zhou et al., J. Mater. Sci. 27, 3155–3166 and 29, 5541–5550). In the three-cylinder model, the push-out of a single fibre in a specimen with multiple fibres was treated as a three-cylinder composite in which a fibre is located at the centre of a coaxial cylindrical shell of the matrix matrerial which in turn is surrounded by a transversely isotropic elastic material with elastic properties of the bulk composite. The radius of the matrix cylinder in this case is related to the volume fraction of the fibre which significantly affects the behaviour of interfacial debonding and fibre push-out. A simple methodology is presented on the basis of these analyses to determine the interfacial properties, including interfacial fracture toughness G ic, residual clamping stress q 0 and coefficient of interfacial friction μ, from the experimental results of maximum debond stress σ d ∗ (or initial debond stress σ d 0) and initial frictional push-out stress σ fr measured in a fibre push-out test. The effects of the fibre volume fraction, the transversely isotropic property and the Poisson expansion of the fibre are all considered in the analyses.