FRP rods for brittle fracture resistant composite insulators

Brittle fracture of fiberglas reinforced polymer (FRP) rods can lead to mec hanical failures of composite insulators even at low mechanical loads durin g operational service. Although this fact has been known for 20 years, it m ay still be a problem in some designs of composite insulators at the presen t time. In order to find countermeasures against brittle fracture, a study was carried out in the early eighties. It turned out that brittle fracture is a problem of FRP material and that material compositions exist, resistan t to brittle fracture. A brittle fracture resistant FRP rod introduced 1983 in one particular design of composite insulators resulted in a 15 year exc ellent service performance. This study deals with details of brittle fractu re of ERP rods. Test setups were established to induce brittle fracture art ificially. It was realized that brittle fracture is some kind of stress cor rosion related to the composition of the FRP material. A broad variety of F RP materials was evaluated, showing the influence of the components of FRP material on the brittle fracture behavior of FRP rods as well as the effect s of different manufacturing processes. The compositions of brittle fractur e resistant FRP rods are disclosed. The results from artificial testing are compared with brittle fracture of FRP rods that occurred in composite insu lators in operational service. Although no quantitative correlation could b e established, the trend concerning the material behavior of FRP rods is si milar.