ABSTRACT

Fibre reinforced resins are often used, not only for their good mechanical properties and light weight, as well as their ability to be made into useful and sometimes complicated forms, but also because of their chemical inertness. Tanks for the storage and transport of corrosive chemicals are often made of composites. The fibre-matrix interfaces in resin matrix composites provide preferential channels for the ingress of outside agents which can modify the interactions between the fibres and the matrix. Diffusion laws have generally been applied to the modelling of simple water uptake and the simple Fick's law can be applied to a large number of composite materials subjected to humid environments. Most composite structures are however basically two dimensional as they are made of layers of fibres, often in the form of unidirectional lamina or woven cloth. It is only when the composite has reached saturation under the prevailing humidity conditions that a uniform water concentration across the specimen exists.