Fibre-reinforced composite materials are used in structural applications in marine, offshore and oil & gas industries due to their light weight and excellent mechanical properties. However, an exposure of such materials to water leads to environmental ageing, weakening the composite over time. A typical design lifetime of offshore composite structures, being in direct contact with water and humid air, spans 25 years or more. Thus, prediction and modelling of the environmental ageing phenomena becomes highly important, especially for predicting the long-term environmental durability. In this work, a systematic and modular approach for quantitatively modelling such phenomena is provided. The modular methodology presented in this work can and should be further expanded – it is multiscale and scalable. In the state-of-the-art, the degradation framework is not complete, yet it is a systematic step towards the multiscale modelling paradigm for composite materials. The topic of environmental durability of composite materials is being actively developed and is expected to continue growing also in the future.

There are 3 constituents in a composite: matrix, fibres and an interphase. Each constituent degrades differently and may also affect the degradation behaviour of each other. Therefore, a modular multiscale approach is preferred. The modules are based on the physics, chemistry of individual constituents’ interaction with the environment, including diffusion, molecular mechanisms and kinetics of environmental ageing.

The methodology is seen as a useful approach for both industry and academia, including such use cases as accelerated testing, prediction of lifetime of composite materials and structures, as well as improving understanding of the environmental ageing effects and the time-dependent properties of composites due to environmental ageing.