CLT Fabricated with Gmelina arborea and Tectona grandis Wood from Fast-Growth Forest Plantations: Physical and Mechanical Properties

Fabrication and use of Cross Laminated Timber(CLT)using tropical woods is still limited at present.Therefore objective of the present study aims to determine the possibility of using CLT panels of 3 and 5 layers,fabricated withTectona grandis and Gmelina arborea wood using adhesive of isocyanate polymer emulsion system catalyzed with polymeric isocyanate.Delamination,water absorption,density,flexure test,compression and glue-line shear were evaluated using ANSI/APA PRG320-2012 ASTM D198 and ASTM D4761 standard.The results showed that CLT panels of T.grandis presented higher values of density,less water absorption and lower delamination,with no evident differences between the CLT of 3 and 5 layers.The high density of T.grandis resulted in higher values of the mechanical properties.The flatwise and edgewise flexure tests in 5-layer CLT panels of both species pre-sented higher values of bending stiffness compared to those of 3-layer CLT panels.Further the bending stress values in 3-layer CLT panels were higher than for 5-layer CLT panels.As for shear stress in bending flatwise,in both species,3-layer CLT surpassed 5-layer CLT panels,but in the edgewise test no differences were observed.The MOE and Fc in the compression test were superior in relation to the edgewise test.MOE and Fc in compres-sion flatwise in 3-layer CLT was greater than in 5-layer CLT in both species,but edgewise these values were higher in 5-layer CLT panels.The most common failures were stress and delamination in the flexure test,whereas in the compression test these were:shearing,splitting and crushing.In the glue-line shear test no differences were observed between CLT panels of 3 and 5 layers for both species.

Development of heartwood,sapwood,bark,pith and specific gravity of teak(Tectona grandis)in fast-growing plantations in Costa Rica

To elucidate the development of heartwood,bark,sapwood,pith and specific gravity of wood in fastgrowing teak(Tectona grandis)plantations in Costa Rica,we sampled three trees in each of 55 plantations and modelled each variable with age,site and different tree heights.Age and stand density of plantations were significant correlated with stem diameter at breast height and total height of the tree.Formation of heartwood was initiated at the age of 4-year-old and increased in direct proportion with age.The age of plantation had a significant relationship with stem diameter at breast height,heartwood percentage,sapwood thickness,sapwood percentage,percentage of bark,pith diameter and percentage,and specify gravity.The model for these tree parameters was model with these parameters as dependent variable and in relation to age as independent variable.