A multiscale and multiphysics numerical framework for modelling of hygrothermal ageing in laminated composites

In this work, a numerical framework for modelling of hygrothermal ageing in laminated composites is proposed. The model consists of a macroscopic diffusion analysis based on Fick's second law coupled with a multiscale FE² stress analysis in order to take microscopic degradation mechanisms into account. Macroscopic material points are modelled with a representative volume element with random fibre distribution. The resin is modelled as elasto-plastic with damage, and cohesive elements are included at the fibre/matrix interfaces. The model formulations and the calibration of the epoxy model using experimental results are presented in detail. A study into the representative volume element size is conducted, and the framework is demonstrated by simulating the ageing process of a unidirectional specimen immersed in water. The influence of transient swelling stresses on microscopic failure is investigated, and failure envelopes of dry and saturated micromodels are compared.