Cure-induced and thermal stresses in a constrained epoxy resin

We report results from a study of isotropic residual stress development for thermosetting resins during cure and subsequent thermal cycling. We use a recently developed thick-walled tube method to impose three-dimensional isotropic constraints on the resin. The strains at the outer surface of the thick-walled tube are monitored by strain gauges. Experiments are performed for a closed tube where the resin is cured in the compressive state and in an open tube where tensile stresses build up at gelation. The cure-induced tensile stresses are much lower than expected from cure shrinkage due to the inability of the curing resin to sustain large tensile stresses in the gel-state.