Abstract: Structural composite lumbers are used extensively in wooden structures. There are many reasons for choosing these materials, including their light weight, easy assemble, and low cost. Various studies have been conducted to increase the load carrying capacities of these materials. Reinforcement with various natural or synthetic fibers is one method that has been studied. In this study, laminated veneer lumber was produced using poplar veneers and glass fiber mesh. One-component polyurethane glue was used in the production of the boards. The modulus of rupture, modulus of elasticity in bending, impact bending strength, and splitting strength values of the control laminated veneer lumber and laminated veneer lumber reinforced with the glass fiber mesh were investigated. In addition, some physical properties such as the densities and moisture contents of the test samples were investigated. Although the reinforcement of laminated veneer lumber using glass fiber mesh had statistically significant effects on impact bending strength, and splitting strength. The effect on the modulus of rupture and the modulus of elasticity in a static bending test was not significant. In addition, the effects of the reinforcement on the densities and moisture contents of the test samples compared the control samples were statistically significant.

Abstract This study used a high-density polyethylene (HDPE) polymer matrix, pine-wood flour (PWF) and walnut-shell flour (WSF) to produce wood-plastic composite (WPC) boards. The PWF and WSF filler amounts were adjusted to 20%, 30%, and 40% by weight. Some of the mechanical properties of the produced composite boards were comparatively investigated, such as the flexural strength, flexural modulus, deformation at break, tensile strength, tensile modulus, and elongation at break. Flexural tests and tensile tests were performed according to ASTM D790 and ASTM D638, respectively. According to the data obtained, the flexural strength, deformation at break, tensile strength, and elongation at break decreased as the filler content increased. In addition, the flexural modulus values of all the test groups increased with the filler content. However, the tensile modulus values of the test groups that used the WSF filler were smaller than those of the groups without filler.

RESUMO Neste estudo, painéis compensados e painéis compensados reforçados com tecido de fibra de vidro foram produzidos com lâminas do desenrolamento do álamo usando adesivo de fenol-formaldeído. Testes de fixação de parafusos e pregos foram realizados para obter as características dos painéis compensados e painéis compensados reforçados com tecido de fibra de vidro. Os efeitos do tecido de fibra de vidro sobre o arrancamento direto do parafuso, puxado pela sua cabeça, e resistência lateral do prego foram determinados. Os resultados dos testes indicaram que a resistência do painel reforçado ao arrancamento direto do parafuso, puxado pela sua cabeça, e resistência lateral do prego foram significativamente superiores em relação aos valores encontrados para compensados não reforçados. Além disso, o reforço em painéis compensados resultou em maior elongação na carga máxima.

ABSTRACT In this study, plywood and reinforced plywood with glass fiber fabric were produced with rotary peeled poplar veneers using phenol formaldehyde adhesive. Screw and nail holding tests were conducted to obtain the characteristics of the plywood and reinforced plywood boards. One control group and three different test groups were used. The effects of glass fiber fabric on the screw direct withdrawal, screw-head pull-through, and lateral nail resistance were determined. The results of the tests indicated that the reinforced plywood’s resistances to direct withdrawal of the screw, screw-head pull-through, and lateral nail resistance were significantly higher than those of the unreinforced plywood. In addition, reinforcement of the plywood boards provided longer displacement at maximum load.

Fast-growing tree species are important due to their short growth time before they are harvested. Both the Poplar and Eucalyptus species are fast-growing trees. These two species have been cultivated in many parts of the world, and they are used in several ways, including in the pulp and paper industry, as wood- based panels, and as structural composite lumber. In this study, laminated veneer lumbers were produced using different combinations of Poplar (Populus x euramericana I-214) and Eucalyptus (Eucalyptus grandis) veneers. Some physical and mechanical properties, including density, thickness swelling, water absorption, modulus of elasticity, modulus of rupture, impact bending, and bonding performance were investigated. According to the test data that were obtained, the mechanical properties of laminated veneer lumbers produced with Eucalyptus were greater than those of laminated veneer lumbers produced with Poplar. When the two were combined and Eucalyptus was used as the top and bottom plies, the mechanical properties also were better than those of Poplar laminated veneer lumbers. As a result, it can be said that both Poplar and Eucalyptus veneers can be used to produce laminated veneer lumbers, and Poplar laminated veneer lumbers can be reinforced with Eucalyptus veneers.

In this study, beech wood was treated in hot oil and in hot air to determine the differences in the effects of the two processes on the physical properties of the wood. Heat treatment was conducted at temperatures of 160, 190, and 220 °C for 2 h at atmospheric pressure. After the heat treatment, various properties of the wood, including mass increase in hot oil treatment (wt% gain), mass loss in hot air treatment (wt% loss), oven-dried density, swelling, equilibrium moisture content, fiber saturation point, and moisture content were determined. Regression analyses were conducted to assess the differences in mass change and volumetric swelling, and the findings were analyzed statistically. The results showed that heat treatment in hot oil influenced the physical properties of beech wood more than treatment in hot air. However, the extensive uptake of oil by the wood samples, resulting in mass increases, was a negative issue associated with the hot oil treatment.

In this study, we determined the flexural properties and tensile shear strength of five-ply plywood panels produced with eucalyptus (Eucalyptus grandis), beech (Fagus orientalis.), and hybrid poplar (Populus x euramericana) using urea-formaldehyde (UF), melamine-urea-formaldehyde (MUF) and phenol-formaldehyde (PF) adhesives. Flexural properties were tested on both parallel and perpendicular to grain samples. Tensile shear-strength tests were conducted on four glue lines of the plywood panels, and the effects of species of trees, type of adhesives, and direction of load were determined. The results of variance analyses showed that the effects of species of trees, direction of load, and type of adhesive on flexural properties were significant, but it was determined by specific flexural properties that the effect of the type of adhesive was based on the density of the plywood. In addition, as a result of findings, it can be said that specific mechanical properties may be a good predictor for comparative studies.