破壊力学に基づくエポキシ樹脂の耐熱衝撃性の評価方法

Abstract

In order to evaluate the thermal shock resistance of epoxy resin, the thermal shock test of quenching notched disk specimens in low temperature liquid was developed and the theoretical analysis was made based on the theory of elasticity and linear fracture mechanics. The thermal shock test was carried out on a very brittle epoxy resin by changing notch length and cooling time. The results obtained were summarized as follows:(1) By using this thermal shock test, the critical temperature difference which corresponded to the minimum energy necessary to propagate crack, was clearly obtained.(2) The critical temperature difference was represented by the dimensionless stress intensity factors K*I. The distribution of K*I increased with an increase of notch length, and showed a maximum peak. K*I obtained by the experiment agreed well with the theoretical one.(3) For the thermal shock resistance of epoxy resin, the usefulness of the minimum critical temperature difference calculated from the thermal shock fracture toughness was clearly shown.(4) From both of the theoretical and experimental results, the suitable cooling time for this test was found to be the time when the dimensionless stress intensity factor becomes maximum, and it was 280sec for the resin used.