MECHANICAL EVALUATION OF AXIALLY LOADED COMPOSITE INSULATORS WITH CRIMPED END-FITTINGS

Composite insulators consist of a glass reinforced polymer (GRP) rod, with two metal end-fittings attached to the ends of the rod during ass embly. This paper aims to evaluate the strength and design of mechanic ally crimped insulator end-fittings subjected to axial tensile or comp ressive loads during service. A non-destructive ultrasonic technique h as been used to measure the extent of radial shortening applied to two composite substation insulators during crimping. The axial compressiv e strength of these insulators have been determined from destructive m echanical tests. In addition, detailed nonlinear axisymmetric and thre e-dimensional finite element analyses have been performed to evaluate the effects of several design variables on the mechanical performance of the crimped joints subjected to axial loads. Results obtained from this study demonstrate that the insulators are likely to encounter fai lure due to sliding of the GRP rod (within the end-fittings) under exc essive axial loads. Based upon the finite element results, semi-empiri cal relationships have been presented to predict the axial loading cap acity of the crimped insulator ends, and the maximum internal stresses on the GRP rod surface.