An Improved Perry-Robertson Theory for Buckling Prediction of Unidirectional-Fiber-Reinforced Composite Insulators

Unidirectional glass fiber reinforced polymer (GFRP) composite insulators are widely used in extra-high voltage (EHV) and ultra-high voltage (UHV) transmission lines due to their outstanding electrical and mechanical performance. However, the accurate prediction of the critical buckling load is crucial to satisfy the high reliability requirement under complex operations. In this paper, an improved Perry-Robertson theory to predict the critical buckling loads of GFRP composite insulators with different slenderness is proposed. Firstly, initial imperfection is expressed as a function of the insulator strut length, which enables the critical load to be formulated as a function of slenderness explicitly. It also allows for convenient comparisons with other theories, such as Euler and Johnson's, and easy calibration with the magnitude of initial imperfections. Secondly, the nonlinear material behavior of the GFRP composite insulator strut, resulting from changes in glass fiber orientation in relation to the loading direction during buckling, is considered to further enhance the prediction accuracy. The predicted results with current theory were validated through compression tests of GFRP composite insulators with solid and hollow struts and different slenderness and boundary conditions, which shows an accuracy of over 85%. Thus, the proposed improved Perry-Robertson theory can be also applied in other fiber-reinforced composite buckling analyses.