Water Absorption of Epoxy-Amine Resin Systems and the Respective Effect on Tensile Strength and Glass Transition Temperature

Wind turbine blades are exposed to harsh environmental conditions which result in aging effects on the matrix of the composite materials. One of the parameters to affect the mechanical performance of polymers is water absorption. Its effect on well-established epoxy resins is studied in the light of state-of-the-art type approval certification guidelines. An alternative approach to the established method using Fick's law is proposed for the approximation of the water uptake over time. This approach simplifies the water absorption modelling requirements and is found to be in excellent agreement with derived experimental data. The materials are exposed to different conditioning environments, i.e. temperature and relative humidity combinations. Their physical and mechanical properties are summarized, and corresponding degradation approximations are proposed based on real rotor blade data. Recommendations and suggestions are made for the current type approval practices.