Changes in Some Mechanical Properties Depending on the Orientation of the Laminated Veneer Lumber Layers

Abstract

The present study was conducted with the purpose of investigating alterations in mechanical properties resulting from layer orientation used in laminated veneer lumber (LVL) production. The LVL was produced by pressing 12-layer veneer laminates with phenol formaldehyde (PF) adhesive at 130 °C and 1.2 MPa pressure for 20 min. To observe the orientation effect during the production, some layers were rotated 90°. Subsequently, the modulus of elasticity (MOE), modulus of rupture (MOR), impact resistance, static hardness, screw withdrawal, and bonding quality values of the samples produced were determined. It was found that the groups that had undergone orientation exhibited lower volumetric changes after the swelling test. Furthermore, the implementation of orientation led to an enhancing effect on the MOE and screw withdrawal values for edgewise loadings of the tested specimens. However, the MOR, hardness, and impact resistance values of the oriented samples were lower than those of the control group. The results showed that one-sided orientation in the LVL increased stability and the flexural properties under edgewise loading, as well as the screw withdrawal strength. However, hardness and impact strength decreased with layer orientation. Additionally, it was found that MOR could be predicted with a higher correlation (R² 0.89) using MOE values in flatwise loading, while a lower correlation (R² 0.40) was found in edgewise loading.