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.
Highlights
Composites industry technologies have been used frequently by engineering
A combined analysis considering the standard deviations and coefficients of variation presented by the treatments (Table 5), bigger variability in the control specimens is observed comparing to the other treatments for the case of P. taeda, what does not occur with Eucalyptus spp., in which the evaluated treatments had similar behavior
The use of fibers increases the strength of the finger-joints equating them to wood without finger-joints for Eucalyptus spp
Summary
Composites industry technologies have been used frequently by engineering. The use of new synthetic materials, in conjunction with natural polymers, makes industrial products meet the desired properties in project and performance standards. Wood and its derivatives are among the most important building materials and have become more and more usual. The availability of large bulk parts is becoming rare and costly, even when coming from certified homogenous plantations. The massive parts possess modified physical and mechanical characteristics due to presence of knots, splits and cracks. These defects have detrimental effect in the tensile and compressive strengths (KHELIFA et al, 2015b)
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