Mechanical performance of fibre reinforced polymer confined softwood timber for pole applications

Abstract

Hardwood as sourcing of utility poles becomes difficult and costly due to its slow replenishment and the high clearing rates in the 19th century as well as occasional bushfires. There is a critical need to source other timber species for timber poles. This paper presents a study of using fibre reinforced polymer (FRP) composites as a confinement system onto plantation softwood for utility poles. The proposed method was a wet layup process using multiple layers of 0°/90° biaxial woven roving E-glass fibre sheets. A series of FRP timber specimens, with different confinement lengths ranging from 0% to 70% of the span length of 5.4 m, were prepared and tested in three-point bending to present two equivalent cantilevers. A timber/FRP composite section with full confinement length was also investigated. Results showed that the FRP system, depending on the confinement length, provided a considerable improvement to the softwood regarding the load carrying capacity and bending stiffness. Theoretical calculation showed a good comparison to the experimental bending stiffness. Finally, finite element results showed satisfactory agreement with the experiments in terms of load carrying capacity and bending stiffness and failure modes.