II is known that there are serious issues of the delamination on the metalepoxy resin interface and the crack failure in epoxy resin due to cure shrinkage when epoxy resin is used as an encapsulating medium of insulators in electrical and electronic equipments. Though several papers have been reported on the attempts to predict the stress-strain behavior during curing reaction except for our reports, their simulation models are proposed with no consideration of cure shrinkage, heat generation in reaction, reaction progress, delamination and crack failure.In particular, the authors could not find reports on a practical multistage curing reaction process in consideration of all cure shrinkage, heat generation in reaction, reaction progress, delamination and crack failure. In this work, the authors attempted simulation with a finite element method for the following: a two-stage curing reaction process suitable for practical use from the start of potting to the completion of curing.Epoxy resin was potted between the inner and outer iron cylinders. The potted epoxy resin was cured under a given temperature before gelling and afterwards under a higher temperature during gelling (two-stage cure reaction process). In order to express the two-stage curing reaction process, the equation of cure reaction was corrected and the temperature dependence of viscoelastic properties was obtained from dynamic viscoelastic analysis. The change in circumferential strain on the surface of outer iron cylinder predicted by the simulation are in good agreement with the experimental one. 313Brought to you by |

The relationship between stress and strain for polypropylene film was studied under strain rates from 0.13 to 5.21 s 21 in order to study the deformation behavior of film under higher strain rates than previous studies. Uniform thickness was obtained in the strain rates from 2.08 to 5.21 s 21 at 435 K, or from 2.08 to 3.13 s 21 at 437 K. The temperature rise of film due to the generation of heat from plastic strain influenced the relationship between stress and strain, in particular, at high strain rates and low temperature. Material constants for the constitutive equation of film were determined using the measurements from 2.08 to 5.21 s 21 at 435 K and from 2.08 to 3.13 s 21 at 437 K. Film thicknesses during and after transverse direction stretching were successfully predicted by applying the material constants obtained. The authors concluded that the material constants should be determined by applying the stretching conditions, under which there is little or no effect from heat generation and under which film can be stretched uniformly in thickness. POLYM. ENG. SCI., 53:309-320, 2013. ª

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Epoxy has been used widely in electronic devices because of its excellent electrical properties for insulators. In epoxy resin curing reaction process, phenomena such as heat of reaction, reaction progress (degree of cure, physical properties, etc.), cure shrinkage and viscoelastic behavior, are related intricately.It is known that there are serious problems of delamination at the metal-epoxy resin interface and crack failure in epoxy resin due to cure shrinkage when epoxy resin is used as encapsulating medium of insulators in electrical and electronic equipments. It is very difficult to make experimentally clear the mechanism of the delamination and crack failure occurring in electrical and electronic equipments during curing reaction. Though several papers have been reported on the attempts to predict the stress-strain behavior during curing reaction, their simulation model is proposed under the conditions without cure shrinkage, heat of reaction, reaction progress, delamination or crack failure. Therefore, previous works cannot be always applied to the practical production process. In order to solve these problems, the authors have proposed a new simulation model, which can applies to the curing process from potting (liquid state) to gelling (solid state) under a constant curing temperature. In this work, the authors have attempted the simulation with a finite element method for two-stage cure reaction as follows :Epoxy resin was potted between the inner and outer iron cylinders. The potted epoxy resin was cured under a given temperature before gelling and under a higher temperature during gelling (two-stage cure reaction) . In order to express the two-stage cure reaction, the equation of cure reaction was corrected. The circumferential strain curves on the surface of outer iron cylinder predicted by the simulation are in good agreement with the experimental results.

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