The Mechanical Properties Research Of Think Core LVL From Poplar, Eucalyptus

In the dual background of the increasingly stringent limits in formaldehyde emission in many countries around the world and the contradiction increasingly prominent between supply and demand of plywood in our country in recent years that made our plates enterprises which mainly are SMEs,had only a few kind of productions and severe export-dependent faced serious challenges.There was a urgent need for a low-cost, simple technology and more environmentally friendly product to upgrade their production.This selection choosed fast-growing wood eucalyptus, poplar as materials,they both had large area planting in our country.4-8mm thick veneer which were Softened and Rolling treated as the basic unit, use optimum Hot-pressing process to obtain a laminated veneer lumber for exploring the effect of tree species, glue content, veneer thickness on the mechanical properties of the three factors, use optimum Hot-pressing process to obtain a plywood for exploring the effect of glue content, veneer thickness on the bond strength of the two factors.(1)The MOR of Eucalyptus wood panels which formed by2mm,4mm,6mm,8mm were above the provision of 130E,100E,90E,80E the excellence in goods level in the national standards GB/T 20241-2006 laminated veneer lumber. The MOR of Polur wood panels which formed by 2mm,4mm,6mm,8mm were achieve the provision of 100E,100E, 100E,90E the the excellence in goods level.(2)The shear strength of all group in the expernment were above the provision of 55V-47H level in the national standards GB/T 20241-2006 laminated veneer lumber. All glue spread level of both species panels which formed by 2mm and 4mm veneer were above 65V-55H level,so and the 200 g/m2 and higher glue spread level of poplar wood plate which formed by 6mm veneer.When Eucalyptus wood at 250 g/m2 or higher glue spread level,It’s also achieve the provision of 65V-55H level in the national standards.(3)With glue spread increases, the mechanical properties of both Species increased before 250 g/m2 then become smoth or decreased. Considered the cost of raw materials and mechanical properties,150g/m2 was the preferred amount of glue.When product eucalyptus wood LVL which formed by 8mm veneer its better to use higher glue spread like 200 g/m2 or more.(4) With the increase of veneer thickness, the mechanical properties of both Species decreased. The decline of Polur wood LVL was Small and Smooth, compare with the LVL which formed by 2mm veneer the decline of MOR,MOE, shear strength were 12%,9%,27%. Eucalyptus wood LVL had a larger decline at 4mm then the decline become Smooth. Compare with the LVL which formed by 2mm Eucalyptus wood veneer the decline of MOR,MOE, shear strength were 40%,22%,39%. Euc alyptus wood LVL had a larger decline than Polur wood LVL.(5)The correlation analysis between the mechanical properties of Eucalyptus wood plate and Polur wood plate show that the two loading direction of MOR and shear strength had a good linear relationship, the correlation coefficient were 0.934,0.876 and 0.925,0.956.The MOR and MOE of Eucalyptus wood plate and Polur wood plate also had good linear relationship, the correlation coefficient were 0.834,0.932.(6)Wet treatment will greatly reduce the MOR of the plate.The decline of MOR were 38% and 34% in Eucalyptus wood plate after 28 hours in boiling water treated and 24 hours in hot water treated.To Poplar plate the number were 47% and 44%. Eucalyptus wood plate had a greater decline than poplar wood plate. Hot treated group had a greater MOR than boiling water treated group.(7)All the level of veneer thickness and glue spread were all have a good Impregnated peel performance.(8) The bond strength of each group were all above 0.7Mpa and exceed the provision of national standards LY/T 1738 2008 plywood for Parquet, GB/T 17656 1999 plywood for Concrete form except the glue spread level at 150g/m2.(9) With glue spread increases, the rate of increase of bond strength decreased in plywood, the rate of increase at each level was 14%,7% and 4%. Considered the cost of raw materials and bond strength,200g/m2 was the preferred amount of glue. (10) With the increase of veneer thickness, bond strength decreased. The decline at each level was 8%,6% and 9%. To 8mm, the cumulative decline was 21%.