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.)

Abstract

The effects of ply organization and loading direction on bending strength and modulus of elasticity in laminated wood materials produced from 3 mm thick veneers, of beech ( Fagus orientalis L.) and lombardy poplar ( Populus nigra L.) placed one on top of the other in various arrangements were examined in this study. Kleiberit 303 (PVAc), a vinyl (polyvinyl acetate – PVAc) based glue was used in lamination. Eight hundred samples were prepared in order to measure oven-dry specific gravity, bending strength and modulus of elasticity values perpendicular and parallel to the glue line of a total of 10 different arrangements, eight of which have different laminated ply organizations, namely (AAAAAAA) (7A), (BBBBBBB) (7B), (ABBBBBA), (ABABABA), (AABBBAA), (AABABAA), (ABBABBA), (BABABAB), in which (A) represents beech wood and (B) represents poplar wood and the other two, which consist of solid beech and solid poplar wood in same dimensions as control samples. The samples were subjected to tests perpendicular and parallel to the glue line in accordance with the ISO 16978 standard. As a result of statistical analysis of the data obtained from the tests, the bending strength and modulus of elasticity values of solid woods both perpendicular and parallel to the glue line were observed to be smaller than those values of laminated woods made of the same species of woods. It was also observed that as contribution rate of beech in lamination increases, the bending strength and modulus of elasticity values increase.