Abstract
In order to carry out a curing reaction analysis of epoxy resin used as electrical insulators, the authors have previously reported kinematic and viscoelastic analyses in parts I and II of this series of reports. The space between two concentric iron cylinders was filled with epoxy resin and the circumferential strain on the outer iron cylinder surface was measured in part II. The results of a finite element model gave good agreement with the results of measurements during gelation. However, the model results showed poor agreement before gelation, probably because of the assumption of full adhesion between the epoxy resin and iron cylinders. In order to improve the agreement, two new adhesion models have been proposed for the epoxy-resin interface.
1) One model assumes that full adhesion is immediately achieved when the epoxy resin begins to gel. The calculated circumferential strain changes on the outer iron cylinder surface do not give good agreement with experimental values after gel initiation.
2) The other model assumes that adhesion is gradually formed as the epoxy resin gels. The calculated circumferential strain changes agree very well with experimental values.
These results indicate that adhesion between the epoxy resin and the iron cylinders is gradually formed. The temperature distribution of the epoxy resin during the curing reaction changes little with time. The internal stresses in the epoxy resin goes up because adhesion increases during the gelation process.
