Strength of Structural Finger-Joints Reinforced With Fibers

Abstract

The finger-joints are the kind of top joints most used in wood blades to manufacture glued laminated timber (GLULAM) and present direct influence on their rigidity and final mechanical strength. Thus, the objective of this study was to evaluate the tensile strength parallel to grain with different compositions of reinforcements concentrated on finger-joints. Two geometries were used to execute the finger-joints and two species: Pinus taeda and Eucalyptus spp. The reinforcements were fabrics from glass or carbon fibers bonded with polyurethane structural adhesive. The treatments used were: "A-Glass", "A-Glass2", "A-Carbon", “A-Without reinforcement”, "B-Glass", "B-Glass2", "B-Carbon" and “B-Without reinforcement”, being "A" or "B", the geometries and "2", the number of layers of tissue. For statistical analysis, the Dunnett test was used at 95% confidence interval. The results showed that the execution of the unreinforced finger-joints decreased the tensile strength of the woods. For P. taeda, all the treatments were significantly inferior to the control (without finger-joints), and for Eucalyptus spp., only the treatment "A-Unreinforced" presented inferior performance to the control (without finger-joints), all others presented equivalent mechanical resistance to solid wood. It can be concluded that for the Eucalyptus spp. wood, the application of reinforcement on the structural finger-joints improves the tensile strength, equating to the solid wood.