On the use of stereolithography for the manufacture of photoelastic models

Three-dimensional photoelasticity using the stress-freezing technique is dependent on the production of resin models that do not possess any residual stresses from the manufacturing process. The traditional methods of production involve casting to shape or machining from solid blocks using thermo-setting resins. These methods are expensive and time-consuming, with models typically requiring days for preparation. The rapid-prototyping technique of stereolithography employs similar resins and allows complex components to be built in a matter of hours. However, the residual birefringence associated with the stereolithographic process has so far inhibited its routine use in photoelasticity. A four-centre study has been conducted in an attempt to understand the mechanisms generating this birefringence and to investigate methodologies for producing models free of stress and birefringence. The mechanical behavior of stereolithographic and thermo-setting resins have been compared at room temperature and under stress-freezing conditions.