Bond Performance of Glued-in CFRP and GFRP Rods in Timber

Abstract

The aim of this study is to compare the bond performance of CFRP and GFRP rods glued-in block laminated spruce C24 under static tension and cyclic loading and identify the relationship between bond strength and stiffness and cost for different materials. FRP rods (Sireg, Italy) with the same diameter (D=10 mm), fibre content, resin matrix (vinylester) and surface deformation (helically wrapped and sand coated) but different fibre type (glass versus carbon) are used in this study. The FRP rods are concentrically glued in engineered timber blocks (70 x70 x 55 mm) with an epoxy (Sikadur 33, Sika) of varying thickness (t=1, 3, and 5 mm) along a bonded length of L=50 mm.Due to their simplicity and ease of application for mechanical screening, the bond strength between the FRP rods and timber is measured by pull-compression tests. Slip values at both free and loaded ends are recorded and strain gauges are attached along the bonded length to record the bond stress transfer mechanism. The static loading tests are carried out at a displacement rate of 0.5 mm/min and the cyclic loading tests are based on BS EN 12512:2001 adapted for glued-in rod connections. Changes in the bond stiffness and bond strength of glued-in FRP rods after 3 cycles are recorded.