A MODEL FOR THE TRANSVERSE STRAIN RESPONSE OF UNIDIRECTIONAL CERAMIC-MATRIX COMPOSITES DURING TENSILE TESTING

A comprehensive micromechanical model relating the longitudinal stress and transverse strain of unidirectional fibre toughened ceramic matri x composites (CMCs) is presented. The model uses different cylindrical unit-cells to describe the composite throughout a tensile test and co nsiders all relevant damage mechanisms. The proposed model takes into account the Poisson contraction of fibre and matrix, the relief of the rmal residual stresses upon damage development, and the build-up of co mpressive radial stresses at the interface due to mismatch between fib re and matrix after debonding and sliding. Thus the modelled transvers e strain response depends on a wide range of microstructural and micro mechanical parameters. The approach is checked by comparing the experi mentally observed and simulated response of a unidirectional SIC/CAS c omposite of which all constituent properties were determined experimen tally. The agreement between experiment and theory is excellent. (C) 1 998 Elsevier Science S.A. All rights reserved.