Design, development and optimisation of fibre reinforced composite poles

Abstract

One way of improving the reliability of an electricity grid is to invest in robust poles capable of withstanding harsh environments. Apart from ensuring a stable supply of electricity to residents, a resilient distribution network can even cut expenses for the utility company. The exceptional weathering resistance of glass fibre reinforced polymer (GFRP) poles can lead to an increase in grid reliability, thereby reducing running costs. This dissertation investigates if and how GFRP can be used to manufacture poles superior to what is available in today’s market by leveraging the material’s inherent benefits. Among the various techniques that can be employed to manufacture GFRP poles, the filament winding method offers the necessary control and efficiency to produce a tapered pole. With filament winding, the engineer is able to design the number of layers and angles at which reinforced filaments are laid onto a tapered mould. Six prototype poles, each 4.2 𝑚𝑚 in length were manufactured using the filament winding technique where each pole was tested under bending conditions to assess performance and to compare behaviour with FEA simulated models. Through this process of verification, the computer models’ accuracy was confirmed by accurately predicting each pole’s load-deflection behaviour and the onset of first-ply failure. This dissertation also showcases FEA modal analysis of GFRP cantilevers which was verified against results found in literature. The strong agreement between FEA and physical results give the confidence necessary to design full sized poles which will encounter various external forces throughout their intended lifetime. A full breakdown of wind forces, and other loads acting on a pole during service is given in this dissertation together with the international standard limits which a pole must adhere to. Micromechanics is used in conjunction with volume fractions to derive typical GFRP material properties in the orthogonal directions, since the composite material is orthotropic. As a result of the analyses carried out on full sized poles, two optimised layup sequences which make up an 8 𝑚𝑚 GFRP pole are given such that the designed poles can withstand various extreme load combinations. The results of this dissertation show that GFRP can be used to manufacture tapered poles which are 50% lighter than steel manufactured poles. Furthermore, there is enough proof that the methods employed here can be extrapolated to design and build poles of greater dimensions.