EXPERIMENTAL INVESTIGATION OF FINGER JOINTS UNDER TENSILE AND BENDING LOADS

Abstract

Finger joints are commonly used to fabricate endless lamella for engineered wood products such as glued laminated timber beams. The finger joints' properties are important for the mechanical characteristics of glued laminated timber beams, particularly those fabricated from higher-strength-graded lamellas. In the present study, 120 spruce timber boards were used to fabricate finger joints. Each timber board was assessed for quality by measuring the eigenfrequency and the density before the finger joint fabrication. The timber boards were cut in half, and both sets were arranged in the same order and afterward fabricated to endless lamellas, such that the finger joints were fabricated from the same timber boards in both sets. On one set, the tensile strength and on the other one, the flatwise bending strength and stiffness were investigated. This paper presents a statistical summary of the finger joint tensile and bending test results and correlation analyses between the mechanical properties and the relevant quality assessment indicators. A significant relationship between the finger joint tensile and bending strength is observed. Furthermore, the dynamic modulus of elasticity is identified to be a useful indicator of finger joint strength and stiffness.