Insertion of an interphase synthesised from a functionalised silicone into glass-fibre/epoxy composites

The fibre/matrix interface in unidirectional composite materials is modified by introducing a controlled interphase having a low glass transition temperature. :The synthesis of this interlayer is based on polyurethanes and sol-gel chemistries. The interphase is introduced by a solvent process on-line during filament-winding. :The mechanical behaviour of composite materials studied by means of of S-axis tensile tests and three-point Bending measurements (by varying the span-to-depth ratio) is the same than that for composite materials based on commercially sized glass fibres. Thus, the elastic behaviour is not modified by the introduction of a low-modulus and low-thickness interphase. On the other hand, the impact toughness, studied by using the Charpy test, is enhanced by the soft interphase. These experimental studies confirm the theoretical models developed previously in the literature and the conclusions obtained on microcomposites. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.