Void growth in a viscous resin is analyzed by using the equivalent inclusion method combined with the Mori-Tanaka theorem. In modeling, assume that the degree of the viscosity of the matrix resin changes with temperature according to the so-called W.L.F equation and the solid forming agent in the resin is sphere in its shape and it vaporizes to become a gas at the prescribed temperature. The pressure in the void formed by the forming agent is related with its volume by using the Boyle-Charles law. The volume of the void and the pressure in it are calculated to a cycle of heating and cooling and they are obtained as a function of the elapsed time in the cycle. The volume of the void increases with increase in the elapsed time and the pressure in the void decreases. The resultant volume of the forming resin is about 2 times to that of the original resin.
