Full-Scale Flexural Testing on Fiber-Reinforced Polymer (FRP) Poles

Abstract

An extensive research project is currently carried out at the University of Sherbrooke to develop and evaluate the flexural behavior of lightweight fiber reinforced polymer (FRP) poles. In this project, a total of 23 full-scale prototypes of FRP poles with length ranging from 5 to 12 m were submitted to static flexural testing. The load carrying capacity, the failure modes and the deflection of these FRP poles, having hollow circular cross section and variable wall thickness, are being investigated experimentally and theoretically. The FRP poles were produced with the filament winding process, using epoxy resin reinforced with E-glass fibers. Each type of the poles tested in this study is constituted by three zones where the geometrical and the mechanical properties are different in each zone. The difference of these properties is due to the number of layers used in each zone and the fiber orientation of each layer. A new test setup designed and built according to ASTM-D4923–01 and ANSI-C136.20 standards recommendations was used to conduct full-scale flexural testing. Test parameters include the geometrical properties of FRP poles, the type of fibers, presence and positioning (compression side compared to tension side) of the hole are also investigated. Experimental results show that the use of low linear density glass-fibers could provide an increase of the ultimate load carrying capacity up to 38 % for some FRP poles. Also, the positioning of the hole in the compression side compared to the tension side leads to an increase of the ultimate load carrying capacity up to 22 % for the 5.4m (18 feet) FRP poles and no significant effect (3,5%) for the 12m (40 feet) FRP poles. This is mainly due to the stacking sequence and the stress states generated around the hole. Theoretical predictions of the deflection at the loading position are also presented using the theory of linear elasticity and the orthotropic material properties of the composite materials. Good agreement is found between experimental and theoretical results.