Environmental ageing of epoxy-based stereolithography parts. Part 2: effect of absorbed moisture on mechanical properties

The first part of this paper demonstrated how the quasi-Fickian moisture uptake exhibited by stereolithography resins could be modelled. This part outlines the effect of moisture absorption on the mechanical properties of one of the materials. Fickian and dual-Fickian diffusion models, using both analytical and FEA techniques were used to model the moisture uptake in aged samples. Uniaxial tensile testing of dog-bone samples revealed a decrease in elastic modulus and yield stress and an increase in strain to failure with increased moisture content. A model has been developed to predict the change in stiffness of aged samples over time. The results produced from this model show a good correlation to the experimental data and FEA predictions. It is proposed that FEA based coupled stress-diffusion analysis methods can be used to predict the effect of moisture on the mechanical performance of parts made by SL when used in service.