Investigation of Bending Strength of Tannin Impregnated Wooden Beams after Heat Treatment

In this study, the changes in bending strength were investigated by applying heat-treatment to laminated beams modified with acorn tannin to improve the mechanical properties of wooden load-bearing structural members. For this purpose, acorn tannin was impregnated on samples prepared from Scotch pine (Pinus sylvestris L.), oak (Quercus petraea L.), and chestnut (Castanea sativa Mill.) woods. Heat treatment was applied to the samples impregnated with acorn tannin at 150ºC for 3 hours. Untreated, heat-treated, and tannin-modified samples were conditioned until they reached constant weight at 20ºC at 65% relative humidity (RH), 40ºC at 35% RH, and 10ºC at 50% RH. Bending resistance tests were applied to the elements that are conditioned in outdoor conditions according to ISO 13061-3. The results of bilateral interaction between tree species and treatment type were compared, the highest bending strength increase was found in Scotch pine samples by 5% compared to control samples.

Influence of dowel diameter and curing time on strength of double dowel joint

The tensile and bending strength of double wood dowels in medium density fiberboard components was tested by using experimental method which was conducted to define the influence of dowel diameter and curing time on tensile and bending strength of T-shaped and L-shaped double wood joints. The results showed that the dowel diameter and curing time have a great effect on the tensile and bending strength of T-shaped and L-shaped double wood joints. The obtained optimum technical parameters were respectively as follow: dowel diameter was 10.00 mm for tensile strength of T-shaped joints, dowel diameter was 10.00 mm for bending strength of T-shaped and L-shaped joints, and curing time was 168 h for bending strength of T-shaped and L-shaped joints. The relational expression between dowel diameter R and the tensile strength P was obtained in P= 159.7R+11.05, the relational expressions between dowel diameter R and the bending strength P were obtained in P= 30.7R-58.21 and P= 25.48R-41.04 for T-shaped and L-shaped double wood joints, respectively. Moreover, the relational expression between curing time T and the bending strength P in the P= -0.003T2+0.683T+164.1 and P= -0.003T2+0.746T+132.0 for T-shaped and L-shaped double wood joints, respectively.

Performance evaluation of the bending strength of larch cross-laminated timber

A bending strength test was carried out on the strip-type cross-laminated timber (3 layers) that was combined differently by the cross-sectional annual ring orientation of the laminae under the same modulus of elasticity combination. In addition, the bending modulus of elasticity and the maximum bending moment predicted using the gamma method were compared with the results of the actual test. The result of the bending strength test showed no significant difference in bending strength among the specimens combined according to the annual ring orientation. Furthermore, when the outer tension layer of the cross-laminated timber was strengthened with a glass-fiber-reinforced plastic plate (volume ratio: 1.2%), the modulus of elasticity and the modulus of rupture increased by 4.2% and 16.3%, respectively. The ratios of the prediction results for the bending modulus of elasticity and the maximum bending moment by the gamma method to the actual test values were 1.01 and 0.96 on average, respectively, indicating that the two values were almost identical.

Effects of heat treatment on some chemical compound and mechanical properties of black pine wood

In this study, effects of heat treatment on bending strength, compression strength, chemical compound and solubility of Black pine wood (Pinus nigra J.F. var. seneriana) was examined. For this purpose, Black pine wood samples were kept in temperature of 250°C for 2 hours. Test results of heat-treated Black pine wood and control samples indicated that mechanical characteristics including compression strength and bending strength were affected negatively with heat treatment. Bending strength of heat treated and non-treated test samples were 129 and 76, respectively. Compression strength of heat treated and non-treated test samples were 53 and 43, resp. In addition, level of extractives, cellulose and hemicellulose decreased while lignin content increased with percentage of 40%. Significant decreases occurred in all chemical solubility values.

Effect of the fabric reinforcement of structural holes in wood based panels

The objective of this study was to determine the effects of the glass fiber fabric reinforced holes in MDF, PB, OSB, and PL. The fabrics of 19 mm or 50 mm wide were used to reinforce the edge or flat surface of test specimens. The experimental sample groups were formed in 34 different ways. Three different holes configurations were prepared. The samples were subjected to the 3 points bend testing in the flatwise and edgewise directions. As a result of tests, bending strength and modulus of elasticity were determined. The data obtained separately in flatwise and edgewise bending tests were subjected to multiple variance analysis. According to experiment results, the lowest values were obtained in the “fabricless” in both tests. The lowest value was obtained as 12.35 N.m-2 (in PB material) in the group 12, which has samples with the fabric on the edge and 2 holes on the surface in the flatwise test, while the highest value was obtained as 49988 N.m-2 (in PL material) in the group 19, which has samples with the fabric on the bottom edge and holeless in the edgewise test. According to the materials, the lowest values were as 18.32 N.m-2 in PB material, while the highest values were 49988 N.m-2 in PL material. It was determined that the BS and MOE values decreased between 0.3 and 49% in terms of the effect of the hole with fabric on the edge. In the holeless groups, the lowest values 18.32 N.m-2 in flatwised were obtained in fabricless group in PB, while the highest values 49988 N.m-2 in edgewised were obtained in the group of fabric on top surface in PL. The results showed that the fabric reinforcement has a positive impact on the strength.

Investigation on the mechanical properties of open-hole spruce and douglas fir

Spruce and Douglas fir are the main materials of today’s modern wooden structure buildings. In wooden structure buildings, holes often have to be created on the building components in order to reserve channels for pipelines. At present, there are no detailed studies regarding the mechanical properties of these two kinds of lumber under open-hole condition. In this paper, universal mechanical testing machine was utilized to perform three-point bending tests on small samples of spruce and Douglas fir with open-hole (opening diameters being Ø13, Ø16, Ø20 respectively) and without open-hole. The bending strength and modulus of elasticity of openhole and no open-hole samples were compared, the effects of hole sizes on samples mechanical properties were analyzed and discussed, and the samples’ failure patterns and failure mechanisms were also studied. The experiments were loaded at a constant speed 5 mm. min-1 until the sample was broken, with the loading time controlled within 2 – 3 minutes. The results showed that: open-hole had significant impact on the bending strength of both kinds of lumber. In terms of failure modes, most of the Douglas fir samples were deformed only at the compression point before failing, while the Spruce samples not only formed grooves at the compression point but also cracked at the bottom. This indicated that compared with Douglas fir, the impact of open-hole on Spruce lumber was greater, thus open-hole should be avoided on Spruce components during construction. The experimental results provided a basis for future studies on the failure modes of these two materials and also the strength design of relevant components.

Comparative analysis of static and dynamic MoE of pannónia poplar timber from different plantations

The aim of this study has been to investigate the suitability of Pannónia poplar (Populus × euramericana cv. Pannónia) timber for structural purposes. Static and dynamic modulus of elasticity (MOE) has been determined on samples of 4 different Hungarian plantation origins. The results of the dynamic test showed the same range as the static test, showing a good correlation of the two measurements. As result it can be stated that the domestic Hungarian Pannónia poplar species have in average 11000 modulus of elasticity. This exceeds considerably the threshold limit value (7000 necessary for structural applications according to Eurocode 5. Therefore Pannonia poplar is suitable for structural applications, and are a good alternative of the widely used coniferous species in construction sector.

Bending characteristics of laminated wood composites constructed with black pine wood and aramid fiber reinforced fabric

The aim of this study was to determine the 4-point bending strength and modulus of elasticity in bending of Black pine wood laminated materials reinforced with aramid fiber was bonded using epoxy or polyurethane glues separately. The samples were prepared in accordance with the TS 5497 EN 408 (2006). The results of the study determined that the highest value for static bending strength was found in the laminated wood samples (83.94 that were prepared using inter-layer aramid fiber reinforced polymer (AFRP) and epoxy glue. The highest value of modulus of elasticity in bending was found in the samples prepared with inter-layer epoxy and AFRP (10311.62 It was observed that the samples parallel to the glue line of the laminated material showed higher performance compared to those perpendicular to the glue line. The data obtained as a result of this study demonstrated that aramid fiber reinforced Black pine wood laminated materials can be used in the building industry as building materials.