UNIDIRECTIONAL FIBER-REINFORCED POLYMERS - ANALYTICAL MORPHOLOGY APPROACH AND MECHANICAL MODELING BASED ON THE PERCOLATION CONCEPT

An improved self-consistent scheme accounting for the 2D geometric arr angement of fibres within the matrix is proposed to predict the influe nce of the reinforcement effect of DGEBA/anhydride matrix by unidirect ional raw glass fibres or coated fibres with silicone or DGEBA/silane coupling agents. This model is based on both (i) an analytical morphol ogy approach underlying the percolation concept and (ii) the definitio n of an original 'representative morphological pattern' accounting for local phase inversions owing the heterogeneous morphology of composit e materials. It is shown that the nature of fibre sizing can influence the viscoelasticity of composite materials by inducing variations in morphology and then in the mechanical coupling. This could result from the more or less good wettability of fibres by the resin during the p rocess. After removing the reinforcement effect through such a theoret ical approach, microstructural changes of the polymer matrix induced b y fibres, i.e a decrease in the crosslinking degree of the epoxy netwo rk, are quantified but no specific influence of the nature of the inte rface can be revealed. (C) 1998 Elsevier Science Ltd. All rights reser ved.