Mechanical Properties Of Laminated Veneer Lumber Research Articles

Modified grain orientation of laminated veneer lumber characteristics of three fast-growing tropical wood species

Laminated veneer lumber (LVL) and modified grain orientation of LVL (LVB) are composite products made from veneer that are predicted to replace construction timber. The purpose of this study was to determine the physical and mechanical properties of LVL and LVB of mahoni (Swietenia macrophylla), manglid (Manglietia glauca), and gmelina (Gmelina moluccana) and to compare their characteristics. The results showed that the physical and mechanical properties of LVL and LVB generally meet the standards for use in construction. Differences in the properties of LVL and LVB occurred in the properties of hardness and screw tests, while the other properties were similar. The parallel fiber direction was better in terms of adhesive strength, while the compaction density was slightly higher than LVL. The LVL flexural strength was better than LVB in flat and edge test directions. This difference correlates with the adhesive strength in the shear strength test due to the different orientation of the fiber directions.

Some properties of laminated veneer lumber manufactured from oil palm trunk

Indonesia is the largest oil palm producer in the world and it was predicted that around 7 million metric tons was left in the field as a replanting waste, including palm frond and trunk. The utilization of this waste as a raw material of composite products may overcome the problem. The objective of this study was to determine the physical and mechanical properties of Laminated Veneer Lumber (LVL) made of oil palm trunk. Laboratory scale five-ply LVLs glued with urea formaldehyde adhesive were fabricated with five types of layer compositions i.e five-ply LVL with all layers made of oil palm trunk veneers (OP), five-ply LVL with face and back layers made of jabon veneers (J2), five-ply LVL with face, back and center core layers made of jabon veneers (J3), five-ply LVL with face and back layers made of mahoni veneers (M2), and five-ply LVL with face, back and center core layers made of mahoni veneers (M3). Results showed that the physical and mechanical properties of laminated veneer lumbers made from oil palm trunk were affected by layer compositions. Incorporating jabon or mahoni wood veneers in the structure of oil palm LVL improved the physical and mechanical properties of LVL.

Highly Mechanical Performance of Laminated Veneer Lumber Induced by High Voltage Electrostatic Field

The high voltage electrostatic field (HVEF), as a novel technology, was applied in the study to obtain a highly mechanical performance of LVL (laminated veneer lumber) by increasing limiting value of shear failure strength directly affected by bonding strength. The surface property of wood, polymerization extent of PF, bonding interface of wood-to-PF and mechanical properties of LVL were investigated under the HVEF treatment. The results showed that increased free radicals and total surface energy were acquired under the HVEF treatment resulting from more polar groups (?OH, ?CHO) and ions were triggered leading to decreased contact angles identified both for Poplar and Masson specimens. The HVEF provided more reactions among wood-to-UF and more cross linking reaction of PF occurred in the treating step. The tendency of vertical density profile was more extremely steep than the control with max density increased by 24.93% and 30.24% for Poplar and Masson LVL respectively since adhesive aggregated continuously and orderly along bonding interface and permeation depth reduced to around 200 ?m, accounting for improved bonding shear strength, which eventually brought an enhancement on mechanical properties of LVL with horizon shear strength (?and?), modulus of elasticity and static bending strength significantly enhanced by 14.65%, 10.68%, 20.67% and 12.34% for Poplar LVL and that of Masson LVL enhanced by 17.30%, 13.93%, 18.55% and 12.72%. Besides, the delamination ratio was decreased by 49.57% and 58.32% respectively both for Poplar and Masson specimens.

Effect of surface carbonization on mechanical properties of LVL

The wood veneer from Monopetalanthus species was heated under different temperatures (120 °C, 160 °C, 200 °C, and 240 °C) and then laminated as the surface of laminated veneer lumber (LVL). Bending modulus of elasticity (MOE), modulus of rupture (MOR), and impact toughness (IT) of the LVL were tested. The results showed that the failure location became scattered as the surface veneer carbonization temperature was increased and that the failure mode changed from split failure in the control and the 120 °C samples to crack failure in the 160 °C, 200 °C, and 240 °C samples under the bending load. Fiber tearing was visible in all five sample types, where the length of the tearing fibers became shorter with increased surface heating temperature under impact load. The carbonization temperature of surface veneer had a minimal effect on the MOE but a considerable effect on the MOR and IT, and the MOR mainly showed a downtrend. The IT loss decreased as the surface veneer carbonization temperature was increased.

Effects of Veneer Treatment with Copper-Based Preservatives on the Decay Resistance and Mechanical Properties of Poplar LVL

To improve the durability of poplar laminated veneer lumber (LVL), the veneers were impregnated with alkaline copper quaternary (ACQ) and copper azole (CA) at four retention levels, and the effects of the treatments on the LVL properties were examined. The results demonstrated that the treatments substantially improved the decay resistance of LVLs, with the decreases in mass losses ranging from 42.6% to 87.3%. However, retention levels greater than the specified standard values for Use Category C4.1 might be required for sufficient protection of poplar LVL against decay fungi. The bending and shear properties of all treated LVLs met the requirements for high-grade products specified in the LVL standard GB/T 20241. No significant effects of the treatments were observed on the mechanical properties of LVLs, and the LVLs did not display any visible delamination after boil-dry treatment. These results imply that the treatments significantly improved the decay resistance of poplar LVL products and had no appreciable impact on their mechanical and physical properties.

Engineered Wood Composite of Laminated Veneer Lumber: Physical and Mechanical Properties

Utilisation of forest plantation species such as Acacia hybrid has been used in wood-based industry as an alternative to solid wood that was usually attained from natural forest. While, the under-utilised species such as Mangifera sp. is not often been used as raw material for wood products, in this study, laminated veneer lumber (LVL) has been produced from Acacia hybrid and Mangifera sp. The physical and mechanical properties of LVL were determined and compared. For physical testing, the range value of moisture content was 9.41% to 14.56%, Density was 487.90 kg/m3 to 699.10 kg/m3, thickness swelling was between 0.20% to 6.05%, water absorption between 32.71% to 91.25%, and rate of delamination from 0% to 100%. Mangifera sp. LVL has higher moisture content, rate of delamination, and water absorbency. In mechanical testing, it is been found that Acacia hybrid LVL has overall higher strength compared to Mangifera sp. LVL, in terms of static bending strength (MOR and MOE), shear strength, and compression strength. Range of value for MOR was between 10.27 N/mm2 to 129.99 N/mm2, MOE between 1138 N/mm2 to 16472.93 N/mm2, shear strength between 0.43 N/mm2 to 3.40 N/mm2, and compression between 139.45 N/mm2 to 6749.74 N/mm2. For physical testing, the overall result of p-value for moisture content, water absorption, and delamination were significant at p ≤ 0.05, while density and thickness swelling were not significant at p ≥ 0.05. For overall result, the p-value for static bending strength (MOR and MOE) was significant at p ≤ 0.05 while for shear strength and compression strength were not significant at p ≥ 0.05.

Study on the Technology and Properties of Soybean Adhesive Bonded Laminated Veneer Lumber from Poplar Wood

It was investigated that the technology of hot prepressing temperature and hot pressing duration had influence on the mechanical and physical properties of soybean adhesive bonded laminated veneer lumber(LVL) from poplar wood. The results show that lower mat prepressing temperature may be beneficial to the mechanical properties of LVL. The effects of hot pressing duration on the properties of LVL are less than those of prepressing temperature. When the prepressing temperature is 70°C and hot pressing time is 100s/mm with glue spread amount of 450g/m2, hot pressing temperature of 160°C and mat pressure of 1.6 MPa, the mean modulus of rupture value is 78 MPa, mean modulus of elasticity value is 14.4 GPa, mean horizontal shear strength value is 7.8 MPa and immersion peel rate is 0.4%, respectively.

Physical and Mechanical Properties of Laminated Veneer Lumber Manufactured by Poplar Veneer

Efficient usage of laminated veneer lumber (LVL) in the construction industry requires an understanding the effects of the heat treatment process on the physical and mechanical properties of LVL. It is well known that the heat treatment is often used to improve the dimensional stability of solid wood, but it cases to decrease mechanical properties of solid wood. However, this study aimed testing the physical and mechanical properties of LVL manufactured from heat-treated and untreated poplar veneers. The LVL samples were produced from poplar heat treated veneers (Populus nigra) in the seven ply form (3 mm each) by using urea-formaldehyde (UF) adhesive. Before manufacturing LVL, veneers were subjected to heat treatment at varying temperatures and for varying durations of heating. Significant differences were determined (P ≤ 0.05) in the physical and mechanical properties of the LVLs. The results were recorded the lowest density increment as 29%, the lowest radial swelling as 48%, the lowest tangential swelling as 45% and the lowest longitudinal swelling as 33% for LVL manufactured from heat treated veneers at 180 °C for 5 h as compared to the control sample. The highest flat-wise and edge-wise modulus of rupture (MOR) (107.67 MPa and 102.1 MPa) and modulus of elasticity (MOE) (6,190 MPa and 6,017 MPa) were obtained in the control sample manufactured from untreated veneers. It was determined that modulus of elasticity was less sensitive than modulus of rupture of composite lumber to change due to increase in temperature and heat durations. According to the statistical analyses of variance, the mechanical and physical properties of LVL were more sensitive to temperature than duration of exposure.

Effect of pressure duration on physical, mechanical, and combustibility characteristics of laminated veneer lumber (LVL) made with hybrid poplar clones

Experimental eight-ply laminated veneer lumbers (LVLs) from rotary peeled I-214 (Populus x Euramericana) and I-77/51 (Populus deltoides)fast growing hybrid poplar clones were successfully manufactured using three different press durations (18, 24, and 30 min) with a melamine urea formaldehyde (MUF) adhesive. The effect of press durations on LVLs’ selected physical, mechanical, and combustibility characteristics were determined. The results showed that press duration affected dimensional stability (thickness swelling and water absorption), modulus of rupture, and/or compression strength parallel to grain, depending on the clone types. Improvement in dimensional stability and some mechanical properties of LVLs can be achieved by proper curing of the MUF adhesive. On the other hand, the press durations did not affect oven-dry densities, modulus of elasticity, and the combustibility (weight loss after completion of the test). For improved physical and mechanical properties, up to a 30 min press duration can be recommended. This is necessary for LVLs when they are to be used under conditions where water and/or high humidity is present.

Evaluation of Physical and Mechanical Properties of Non-certificated Laminated Veneer Lumber (LVL) Circulated in Domestic Lumber Market

The selected physical and mechanical properties of non-certificated LVL circulated in domestic lumber market were investigated and compared to relevant standards. The tested LVL passed the moisture content and the soaking delamination rate limit as per domestic (KS) and Japanese standard (JAS). The evaluated mechanical properties were flatwise/edgewise bending strength, modulus of elasticity (MOE), horizontal shear and compressive strength. The 30 mm-thick LVL showed significantly higher bending strength than that of the 25 mm-thick LVL. The modulus of elasticity (MOE) showed same tendency in the results of bending strength. The edgewise bending strength and MOE were higher than that of flatwise bending strength and MOE. The horizontal shear strength values were also showed similar results to bending strength values. The tested results were compared each other and each products were graded according to JAS 701 grade specification. The failure mode of LVL in bending test showed the similar failure mode of solidwood that failed in a simple tension manner (splintery tension). The glue line failure was severe in 25 mm-thick specimens due to concentration of shear stress in layer discontinuity containing small voids and starved glue lines. In horizontal shear strength test, failure mode of LVL showed the typical horizontal shear failure. Compressive specimens failed with fiber crushing in company with apparent delamination that splitted along the length of the specimens. From the results, the complete bonding between lamination and consistency in thin veneer layer were considered as a critical factor in the mechanical properties of LVL. Moreover, the standard test procedure and specification for non-certificated LVL should be required to check the performance of uncertificated materials.

Design and Property Analysis of the Metal Mesh Reinforced LVL

This study mainly analyzed the factors that affected the mechanical properties of laminated veneer lumber（LVL）. To increase the mechanical properties, metal mesh was inserted into LVL that made of fast-growing timber. Effects of different factors were evaluated on the mechanical properties of LVL, several enhancement modes of metal mesh were designed to reinforce the LVL. Then, the mechanical properties (modulus of rupture and modulus of elasticity) of the LVL specimens were measured by static bending test. The results of different enhancement modes were analyzed and compared to investigate the effects of different factors. The position of metal mesh and the mesh number of metal mesh make significant effects on the MOE; the type of metal mesh and the angle of metal mesh-wood grain do not have any obvious effects on the MOE. The type of metal mesh and the position of metal mesh make significant effects on the MOR; the mesh number of metal mesh and the angle of metal mesh-wood grain do not have any obvious effects on the MOR.