EFFECT OF INTERFACIAL DECOHESION ON STIFFNESS REDUCTION IN A RANDOM DISCONTINUOUS-FIBER COMPOSITE CONTAINING MATRIX MICROCRACKS

This work focuses on the modelling of interfacial effects on the overa ll behaviour of oriented discontinuous-fibre composites containing mat rix microcracks. A micromechanical analysis based on Eshelby inclusion theory and the Mori-Tanaka method has been performed. It is intended to evaluate the interfacial stress tensor by considering the local per turbation due to the onset and the growth of matrix microcracks. Howev er, as developed previously, the interfacial degradation effects are m odelled by using the damage participation rate. The latter is determin ed on the basis of an experimental damage methodology. This methodolog y is based on the amplitude treatments and microscope observations, wh ich lend to an identification and a schematic classification of damage mechanisms. The model developed is then used to predict stiffness red uction and to simulate the behaviour of a composite with degraded inte rfaces and containing matrix microcracks. The model simulations agree well with experimental results, notably for the materials referred to as 600 tex and 1200 tex. Indeed, the simultaneous integration of matri x degradation and interfacial debonding has improved the numerical res ults because for these two materials the damage development is mainly governed by both failure processes as confirmed by the experimental fi ndings. (C) 1996 Elsevier Science Limited