Evaluation of Estimation Method for Thermal Fatigue Crack Growth Rate in Epoxy Resin Composites

Abstract

In resin-metal composite structures, such as electronic products with an epoxy resin molding insulator, the thermal fatigue of the epoxy resin during thermal cycling is a critical issue. Because the thermal stress in the epoxy resin and its strength simultaneously change during the thermal cycling, an estimation method for the thermal fatigue reliability in consideration of the temperature dependence of the fatigue strength is required. In this study, the technique of predicting the thermal fatigue crack growth rate in epoxy resin is studied and we proposed an estimation method using the strain intensity factor range ΔK/E as an evaluation parameter. In order to evaluate the proposed method, both the crack growth test by thermal cycling and the thermal stress evaluation by the visco-elastic FEM analysis were carried out. As a result, it was found that the proposed method estimated the crack growth rate under thermal fatigue test less than that of the iso-thermal fatigue test.