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

This paper deals with the modelling of the effect of matrix degradatio n on the overall behaviour of randomly oriented discontinuous-fibre co mposites (RODFC). A micromechanical analysis based on the modified Mor i-Tanaka model is performed. This modelling relies upon an experimenta l approach, developed through a methodology of experimental identifica tion of basic damage mechanisms, which involves amplitude analysis of acoustic emission signals and microscopic observations. The introducti on 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 the se mechanisms in the failure of the representative elementary volume. Besides the good correlation with experimental results, numerical esti mations and tensile test simulations are presented for three classes o f RODFC in order to demonstrate the effects of material structure and to confirm the damage investigation findings. Indeed, from the theoret ical results it can be confirmed that the stiffness reduction of the m aterial '160tex' is mainly governed by matrix degradation, which is no t the case for the two other classes of material studied.