MICROMECHANICAL MODELING OF MATRIX DEGRADATION IN RANDOMLY ORIENTED DISCONTINUOUS-FIBER COMPOSITES

This paper deals with the modelling of the effect of matrix degradation on the overall behaviour of randomly oriented discontinuous-fibre composites (RODFC). A micromechanical analysis based on the modified Mori-Tanaka model is performed. This modelling relies upon an experimental approach, developed through a methodology of experimental identification of basic damage mechanisms, which involves amplitude analysis of acoustic emission signals and microscopic observations. The introduction of an experimental parameter, beta, representing microcrack density allows the modelling of mechanisms relative to the matrix degradation. This damage parameter is a function of the participation rate of these mechanisms in the failure of the representative elementary volume. Besides the good correlation with experimental results, numerical estimations and tensile test simulations are presented for three classes of RODFC in order to demonstrate the effects of material structure and to confirm the damage investigation findings. Indeed, from the theoretical results it can be confirmed that the stiffness reduction of the material '160tex' is mainly governed by matrix degradation, which is not the case for the two other classes of material studied.