THE EFFECT OF FIBER SURFACE-ROUGHNESS ON THE MECHANICAL-BEHAVIOR OF CERAMIC-MATRIX COMPOSITES

The interface between the matrix and the fibre plays an important role in controlling the strength and toughness of ceramic matrix composite s. It has been found experimentally that depending on manufacturing pr ocess, the interface may show substantial surface roughness, which has been modelled analytically with certain degree of success. The analyt ical models, however, do not take into account the interface geometry. Instead, only the magnitude of the surface undulation is included. In this paper, a direct simulation of fibre-matrix interface roughness b y the finite element method is performed on an axisymmetric unit cell with a fully debonded interface. The simulation is employed to account for the three dimensional stress state, surface roughness and interfa ce friction, which are normally simplified or idealised in theoretical studies. The model gives the highly non-uniform interface shear and p ressure, which have direct implications on the interface damage and co mposite behaviour. Under the approximation made in the model, the posi tive transverse strains does not show up in the simulation despite the fact that two different surface roughness are used. (C) 1998 Elsevier Science S.A. All rights reserved.