A microstructure based multiscale model for diffusion in fibre reinforced polymers

Fluid absorption leading to hygrothermal ageing is a significant degradation mechanism for glass and carbon fibre reinforced polymers across a range of applications. Understanding the fluid absorption process is therefore critical to both selecting the optimal material for a particular application and predicting its lifetime in a given environment. Experiments indicate that the interface between the fibre and matrix plays an important role in the fluid absorption process. However, no existing model adequately explains the influence of such interfaces on lab scale fluid absorption behaviours. A micromechanical representative volume element model has therefore been formulated here to investigate the effect of the interface on lab scale fluid absorption. The model is then applied to an anisotropic model for a lab scale sample, yielding realistic agreement with experiments. The anomalous two stage diffusion behaviour is discussed and explained in the context of the microscale model. Finally, a link with interfacial failure during the diffusion process is discussed, giving insight into how interfaces could be better designed and the composite lifetime extended. • Microstructure based formulation of anisotropic composite diffusion coefficients. • Parametric study exploring the role of fibre volume fraction and interfacial thickness on diffusion. • Experimental verification and discussion of anomalous diffusion behaviour.