Fiber-reinforced composite and wood bonded interfaces: Part 1. Durability and shear strength

Fiber-reinforced plastic (FRP) composites have shown the potential for rein forcement of wood structures (e.g., bonding of FRP strips or fabrics to woo d members). Although significant increases in stiffness and strength are ac hieved by this reinforcing technique, there is a concern about the reliable performance of the FRP-wood adhesive bond, which is susceptible to delamin ation. The overall objective of this two-part paper is to develop a qualifi cation program to evaluate the service performance and fracture of composit e/wood bonded interfaces. Two types of FRP-wood interfaces are studied: phe nolic FRP-wood and epoxy FRP-wood bonds. In the present paper, Part I, the durability and shear strength of FRP-wood bonds are evaluated by modified A STM tests. First, the service performance and durability of FRP-wood interf ace bond is evaluated using a modified ASTM delamination test. Then, the ap parent shear strengths of bonded interfaces under both dry and wet conditio ns are obtained from modified ASTM block-shear tests. It is shown that the modified ASTM D 2559 standard test can be successfully used to study the ef fect of several parameters (e.g., bonding pressure, assembling time, and co upling agents) on bondline performance under wet-dry exposure cycles. Then for the best combination of parameters, the average interface shear strengt hs can be obtained from block-shear tests of ASTM D 905, modified for hybri d laminates. Mode I fracture of FRP-wood bonded inter faces and guidelines for FRP-wood bond performance evaluation are presented in the companion Par t 2 paper.