This study reports on the effects of water absorption on the anisotropic mechanical response of
an epoxy resin reinforced with E-glass fibres. Composite specimens were conditioned by
immersion in pure water at 50ºC for different time durations, up to full saturation. Water saturation resulted in reduction of stiffness and strength, in the range of strain rate
0.001−700s
− 1. Experiments on re-dried specimens after water saturation showed only a small recoverability of the original mechanical properties. Water absorption increased the sensitivity of the mechanical response of the GFRPs to the applied strain rate. Finite element simulations of the response of a unit cell of the unidirectional composite were performed to understand the role of the hygroscopic stresses induced by water absorption, and it was found that this is negligible due to the active mechanisms of viscoelastic relaxation.