Reproducing tests of brittle fractures of polymer insulators

Mechanical strength of a polymer insulator decreases gradually with age due to creep of FRP core rod, but such reduction in mechanical strength can be taken into design to guarantee the strength required for 30 or 50 years. It is reported, however, that some serious mechanical failures of polymer insulators have occurred under very low load conditions in shorter periods in field. The cause of such failures is considered as a kind of stress corrosion (called “brittle fracture”) due to exposure of FRP core rod to acid. We tried to reproduce such a failure in laboratory in order to investigate the detailed mechanism and the effect of both acid and mechanical load on brittle fracture. We made special test equipments which can apply mechanical load and acid safely and economically. We succeeded in reproducing such brittle fractures in laboratory and investigated the effect of acid and mechanical load on brittle fracture