THE INTERFACE REGION IN GLASS-FIBER-REINFORCED EPOXY-RESIN COMPOSITES .2. WATER-ABSORPTION, VOIDS AND THE INTERFACE

This paper deals with the influence of voids, the fibre surface coating and the nature of the fibre-matrix interface on water absorption in glass fibre-reinforced epoxy matrix composites. We have found that the rate of water uptake and the maximum level of water absorption in E-glass fibre-reinforced EPIKOTE* resin composites is primarily dependent on the void content. This dependence is so strong that the presence of only 1% voids in a composite can more than double the amount of water it absorbs. The nature of the matrix system was also found to have an effect on the water absorption properties of the composite. In particular, the epoxy resin/curing agent ratio plays an important role. To a much lesser degree the fibre coating also has some influence and, surprisingly, removal of the fibre surface coating had no apparent effect on the kinetics of water absorption despite a large detrimental effect on the interfacial strength.