The effect of creosote and copper naphthenate preservative systems on the adhesive bondlines of FRP/glulam composite beams
Publication Name: Forest products journal
Reinforcement of a glulam beam with fiber reinforced polymers (FRP) does not negate the need for preservative treatment, espe- cially when these materials are to be used in high decay hazard environments. Reinforcement of structural wood components with FRP will enhance the beam’s strength, but actual data on long-term durability is sparse and not well documented, and in cases where data is available, it is not readily accessible. In this study, bond properties of FRP-wood composite materials were investigated follow- ing treatment with creosote or copper naphthenate preservatives. The properties investigated included: shear stress and the percentage of wood failure experienced in shear, and the delamination of the FRP-wood interface when subjected to an accelerated-aging test. When tested in a wet condition (following a vacuum/pressure soak), creosote-treatment adversely affected the wood failure values as- sociated with specimens fabricated with a pultruded FRP composite sheet (E-glass fiber, bonded with urethane) during the shear test- ing. When these tests were conducted with samples under ambient conditions, the shear strength of this material was also adversely af- fected by creosote. In addition, both creosote- and copper napthenate-treatment adversely affected the shear strength of a SCRIMP fabricated FRP material (carbon fiber, vinyl ester matrix). Creosote-treatment promoted the delamination of the pultruded FRP com- posite and a continuous laminated FRP composite flat-sheet (E-glass fiber, bonded with epoxy) from glulam material when subjected to accelerated-aging tests. In some cases the delamination percentages were very large. An analysis of the 1 percent delamination threshold level for individual softwood adhesive bondlines is provided for FRP-wood bonding.