Structural performance of the finger-jointed strength of some wood species with different joint configurations

The effects of ply organization and loading direction on bending strength and modulus of elasticity in laminated veneer lumber (LVL) obtained from beech ( Fagus orientalis L.) and lombardy poplar ( Populus nigra L.)

The purpose of this study is to determine the effects of the nano-particulate silicon dioxide (SiO2) material on the bending strength and modulus of elasticity in bending of some wood species. Oriental beech (Fagus orientalis L.) and sessile oak (Quercus petrea L.) woods species which are commonly used in the furniture industry were used in this study. Impregnation was carried out with the preparation of SiO2 at concentrations of 1% and 3% according to ASTM-D 1413-76 (1976) standards. According to the results, while solution concentration was increasing in both wood species, total retention (kg/m3) and percentage retention (%) values increased; air dry density (12%), bending strength and modulus of elasticity in bending decreased. The maximum mean values of bending strength and modulus of elasticity was in control samples of oriental beech and the minimum were in sessile oak wood with 3% concentration. These results can be related to the fact that the higher density of oriental beech wood (0.630-0.685 g/cm³). In both species of wood, impregnation with SiO2 resulted loss of about 3-5% in bending strength and 0.6-9% in modulus of elasticity.

Effects of scarf joints on bending strength and modulus of elasticity to laminated veneer lumber (LVL)

It is aimed to compare the bending strength and modulus of elasticity of end-grain (vertical strip) core blockboard, unlike the usual (lengthwise strip core) blockboard construction, with that of the traditional blockboard with the face-grain or edge-grain core construction. Oriental beech and black poplar woods are provided by taking care to avoid the grain irregularities and visible defects are used in the study. These timbers are used to obtain the core, top and bottom layers of the blockboard. PVAc mounting glue is used for bonding the layers together. According to the test data: The bending strength and modulus of elasticity of oriental beech blockboard are 39% and 26% higher respectively than that of end-grain core black poplar blockboards. If we evaluated by neglecting wood species, strip width was an effective factor in the bending strength and ineffective modulus of elasticity. In addition, the bending strength of the end-grain core oriental beech blockboard is 79 MPa and that of the end-grain core black poplar blockboard is 57 MPa, regardless of the width of the core strip. When these values are compared with the values of other engineered wood, the result is considered open to improvement and satisfactory.

The aim of this study was to investigate the flexural properties (bending strength and modulus of elasticity) of Scots pine wood (Pinus sylvestris L.) using micro- and standard-size test specimens. In the standard- and micro-size specimens, the average bending strengths were evaluated as 72.8 and 62.4 MPa, and the bending modulus of elasticity was 9917 and 2884 MPa, respectively. These results showed that the bending strength and modulus of elasticity values of the micro-size specimens were lower than those of the standard-size specimens. The statistically significant effects included the specimen size, individual trees, and the interactions of the specimen size and trees on the bending strength and modulus of elasticity. Furthermore, regression analyses indicated a positive linear regression between the flexural properties of the micro- and standard-size specimens. The results indicated that micro-size specimens can be used to estimate the flexural properties of Scots pine wood when obtaining standard-size specimens is not possible.

This study has been performed to determine the effects of impregnation with fire retardant chemical materials on the modulus of elasticity (MOE) in bending of Oriental beech, European oak and Scotch pine wood materials. To achieve this goal, test samples prepared from woods of Oriental beech, European oak and Scotch pine according to TS EN 345 regulations were impregnated with ammonium-sulfate [(NH 4 ) 2 S0 4 ], sodium acetate (NaC 2 H3O 2 3H 2 O), aluminum chloride (Al 2 C 6 I 2 H 2 O), borax [Na 2 B 4 O 7 5H 2 O], boric acid [H 3. BO 3 ] and, borax + boric acid (w:w= %50:50). The modulus of elasticity in bending of impregnated wood samples were determined according to TS EN 408. Consequently, according to wood species; modulus of elasticity in bending was found the highest value at beech (10350 N/mm 2 ) and the lowest value at pine wood (9501 N/mm 2 ). According to variety of impregnation; modulus of elasticity in bending values were found no statistical difference ​​ between control samples and impregnated test samples. Considering the interaction of wood type and process; modulus of elasticity in bending was found the highest value at beech + borax (11450 N/mm 2 ) and the lowest value at pine + control samples (8223 N/mm 2 ). As a result, in the massive construction and furniture elements that the modulus of elasticity in bending after the impregnation with borax is of great concern, Oriental beech wood materials could be recommended.

The paper summarizes results of an institutional research aimed at assessing the bending strength and modulus of elasticity in bending of exterior foiled combined and all-beech plywoods in relation to their construction. A relationship was studied of the plywood construction and selected physical and mechanical properties. In studied sheets, moisture, density, bending strength and modulus of elasticity were analysed along and across the grain of the upper veneer. All measurements were carried out in water-resistant plywoods with surface treatment with a phenolformaldehyde foil 8, 10, 12 and 15 mm thick in combined plywoods and 10, 12, 15 and 18 mm thick in all-beech plywoods. The construction of plywoods significantly influences their quality that is determined particularly by the bending strength and modulus of elasticity. Using regression analysis relationships were demonstrated particularly that with the increasing moisture content of plywoods the bending strength decreased and with the increasing density the bending strength and modulus of elasticity increased. The same trend was also proved in connection with the increasing number of veneers of plywood sheets. Using correlation analysis, combinations of interrelationships of the given properties were statistically tested.

This is a study on the effect of plasma treatment with different gases and plasma intensity on the bending strength and modulus of elasticity of plywood manufactured from beech and poplar. Oxygen (O2) and ammonia (NH3) plasma were applied on the veneer sheets; two plasma intensities were applied on the veneers with 150 and 300 W in the plasma chamber during one minute. Phenol formaldehyde resin was applied on one surfaces of each veneer with approx. 160 g/m2. Bending strength and modulus of elasticity were determined according to EN 310.The effects of plasma surface treatment on chemical structure of the panels were determined with FTIR-ATR analysis. Bending strength of all tested panels slightly and partly increased without statistical significance when applying oxygen plasma. The effect of ammonia plasma treatment on bending strength and was determined by the wood species and the plasma intensity, and it was not uniform. Modulus of elasticity of the panels with oxygen plasma treatment showed in most cases improvement, whereas ammonia plasma pretreated veneers caused lower values compared to the control panels.

This study was aimed at determining the effects of the force loading direction on bending strength (MOR) and modulus of elasticity (MOE) in laminated wooden materials obtained in different compositions from cut veneers of Oriental beech and Lombardy poplar with thicknesses of 4 mm and 5 mm. A total of 180 experimental specimens were prepared for determining the MOR and MOE values in parallel and perpendicular directions to the glue line. The study involved a total of 6 air-dried density layer organizations of solid Oriental beech and Lombardy popular in 4 different laminate compositions and in the same dimensions, aimed at control. Polyvinyl Acetate (PVAc) and Polyurethane (PU) were used as the adhesive type in laminations with PVAc5-PU5-PVAc4-PU4. The specimens were subjected to bending strength and modulus of elasticity experiments in parallel and perpendicular directions to the glue line in accordance with the TS EN 310 standards. As a result of the statistical analysis of the data obtained at the end of the experiments, it was determined that in the laminated materials, the force loading direction in parallel or perpendicular to the glue line affected the MOR and MOE results. The best result in the laminated materials was found to be approximately 10% higher for MOR and MOE in a parallel direction to the PU4 glue line compared to the perpendicular direction.

Veneer logs are generally heated in hot water or steam prior to the cutting process in veneering and plywood manufacturing. For economical reasons, the veneers should be dried quickly and without damage. High temperatures shorten drying times. Besides the benefits of log steaming and quick drying of veneers at high temperatures, these processes can be effective on some mechanical, physical and chemical properties of wood. In this study, the effects of the steaming process on logs and veneer drying temperatures on bending strength and modulus of elasticity (MOE) of plywood panels manufactured from spruce and alder veneers were investigated. For this aim, some parts of both wood species logs were steamed for 12 hours before veneer manufacturing while some parts were used unsteamed. Unsteamed and steamed groups of spruce and alder veneers were dried at 20°C, 110°C and 180°C temperatures. The effect of the steaming process on bending strength and MOE was different depending on the wood species. Bending strength and the MOE values of spruce plywood panels increased while both strength values of alder plywood panels decreased after the steaming process. The highest bending strength and MOE values were obtained at 110°C for alder and at 180°C for spruce plywood panels.

The aim of this study was to investigate the effects of impregnation with Imersol‐Aqua (I‐AQUA) on the modulus of elasticity in bending of some woods. For our study, Oriental beech (Fagus orientalis Lipsky), oak (Quercus petrea Liebl.), Scotch pine (Pinus sylvestris Lipsky), Uludağ fir (Abies Bornmülleriana Lipsky), Oriental spruce (Picea orientalis Lipsky), and poplar (Populus nigra L.) wood samples were prepared according to TS EN (Turkish Standards; European Norm) 408 and impregnated with I‐AQUA by the method of short‐, medium‐, and long‐term dipping according to ASTM D 1413 and producers' definition. After the impregnation process, modulus of elasticity was measured according to TS EN 408. Consequently, among the nonimpregnated wood samples, modulus of elasticity was found to be the highest in Oriental beech (Fagus orientalis Lipsky), (12,490 N mm−2) and the lowest in poplar (5439 N mm−2). As for the period of dipping, the highest modulus of elasticity was obtained in short‐term dipping and the lowest in long‐term dipping. Considering the interaction of wood type and period of impregnation, the highest modulus of elasticity in bending was obtained in Oriental beech (Fagus orientalis Lipsky) with short‐term dipping (10,720 N mm−2) whereas the lowest was in poplar with long‐term dipping (4597 N mm−2). In consequence, in massive constructions and furniture elements where the modulus of elasticity in bending after impregnation is of great concern, short term impregnation of Oriental beech and Scotch pine materials could be recommended. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3210–3217, 2006

The influence of loading speed on the bending strength of beech (Fagus sp.) and birch (Betula sp.) wood The subject of this paper was to investigate the effect of loading speeds from 20 mmˑmin-1 to 200 mmˑmin-1 on the flexural strength and deformation of beech (Fagus sp.) and birch (Betula sp.) wood with moisture content close to the absolutely dry state and fibre saturation point. A GOM Aramis measuring system, operating with Digital Image Correlation (DIC) technology, was used in the study to record the displacement and deformation of the elements in real time. The results obtained for flexural strength, flexural modulus and the amount of deformation observed showed a relationship between material properties and loading rate. At higher moisture content, the bending strength and modulus of elasticity decreased with increasing deflexion. The highest bending strength and modulus of elasticity were achieved by the tested wood species at a loading rate of 200 mmˑmin-1. Beech wood, compared to birch wood, showed higher bending strength and modulus of elasticity. Images obtained by means of DIC revealed, at moisture contents close to the dry state, a symmetrical distribution of compressive and tensile stresses relative to the neutral axis of the sample cross-section. At higher moisture contents, there was a significant asymmetry between the compressive and tensile stresses and an apparent shift of the neutral axis towards the tensile surface.

A comparison of bending strength and modulus of elasticity (MOE) of squares with wanes to round timber was performed as part of a project on the use of round Scots pine (Pinus sylvestris L.) timber in structural frameworks. The study was based on 125 squares and 124 round logs from two sites at high altitudes and two sites at low altitudes in southern Norway. The effects of wanes were estimated by means of reduction in second moment of area and section modulus. Wanes had significant effect on both bending strength and MOE, but in both cases the effects were minor when compared with the effects of material properties. The reduction of bending stiffness due to wanes was almost as much as expected from lack of section, while the reduction of moment capacity was smaller. Squares with ⅓ wane had both lower bending strength and lower MOE than round timber. According to how bending strength and MOE are calculated, differences due to wane were expected. The observed difference in bending strength was larger than expected through the lack of section, indicating that it was affected by material properties as well. The difference in MOE between round timber and squares with ⅓ wane could be explained by the lack of section according to how these values are calculated. Origin had a significant effect on both bending strength and MOE.

This paper presents the results of experimental testing of the bending strength and modulus of elasticity in edgewise bending of unreinforced and reinforced seven-layer LVL (laminated veneer lumber) poplar veneer panels. The aim of the research is to determine the influence of woven carbon fibers on the improvement of the bending properties and modulus of elasticity of LVL bending in the plane of the plate, as well as the influence of adhesives on the bending properties of the composite product, in order to test the potential of using this newly obtained material as a structural element. Bending was performed on small-scale samples. The main research task is the examination of three types of reinforcement, which differ from each other in position, orientation, and number of layers of reinforcement, using two different types of adhesives: epoxy adhesive and Melamine Urea Formaldehyde Resins (MUF). The composite material was produced in four different combinations in relation to the orientation and position of the reinforcement in the layup. The applied reinforcement is defined through three different configurations (EK1, EK2, and EK3) and a fourth control sample (EK4). Each configuration was produced by applying the two previously mentioned types of adhesives. The research findings showed that in the case of samples produced by applying CFRP (carbon fiber reinforced polymer) using epoxy adhesive, it significantly affected the increase in bending strength and flexural modulus of elasticity. The average improvement in bending strength is 32.9%, 33.2%, and 38.7%, i.e., the flexural modulus of elasticity is 54.1%, 50.7%, and 54.7%, respectively, for configurations EK1, EK2, and EK3, compared to control sample EK4. During the testing, the test samples from reinforced panels EK1 and EK2 showed partly plastic behavior up to the fracture point, while the diagram for the test samples from reinforced panels EK3 shows elastic behavior to a considerable extent, with a significantly smaller plastic behavior zone. This research proved the impossibility of using melamine-urea formaldehyde adhesive to form a composite product based on veneer and carbon fabric. The greatest contribution of this work is the experimentally verified and confirmed result of the possibility of applying poplar veneer to design structural elements in LVL using epoxy adhesive.

In this study, test samples were prepared from CLT, wooden materials and wooden laminated materials, and bending strength and elasticity modulus values were determined. All samples were prepared using Scots pine (Pinus sylvestris L.) timber as the wood species and PVAc glue as the adhesive. Four-point bending test was applied to the test samples in two different directions, vertical and parallel to the glue line. Flexural and elastic modulus values were examined. The highest bending strength and elasticity modulus values were found in wood laminated material and the lowest in solid wood material. The average values of bending strength and modulus of elasticity were found to be higher in the direction parallel to the glue line than in the direction vertical to the glue line. As a result of the study, it can be said that CLT and wooden laminated materials can be used as an alternative to solid materials, which are frequently used as building and frame construction furniture materials.