Fiber-Reinforced Composite and Wood Bonded Interfaces: Part 1. Durability and Shear Strength

Abstract

Fiber-reinforced plastic (FRP) composites have shown the potential for reinforcement of wood structures (e.g., bonding of FRP strips or fabrics to wood members). Although significant increases in stiffness and strength are achieved by this reinforcing technique, there is a concern about the reliable performance of the FRP-wood adhesive bond, which is susceptible to delamination. The overall objective of this two-part paper is to develop a qualification program to evaluate the service performance and fracture of composite/wood bonded interfaces. Two types of FRP-wood interfaces are studied: phenolic FRP-wood and epoxy FRP-wood bonds. In the present paper, Part 1, the durability and shear strength of FRP-wood bonds are evaluated by modified ASTM tests. First, the service performance and durability of FRP-wood interface bond is evaluated using a modified ASTM delamination test. Then, the apparent shear strengths of bonded interfaces under both dry and wet conditions 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 effect of several parameters (e.g., bonding pressure, assembling time, and coupling agents) on bondline performance under wet-dry exposure cycles. Then for the best combination of parameters, the average interface shear strengths can be obtained from block-shear tests of ASTM D 905, modified for hybrid laminates. Mode I fracture of FRP-wood bonded interfaces and guidelines for FRP-wood bond performance evaluation are presented in the companion Part 2 paper.