Influence of technological cracks of peeled vener on the shear strength of ultralam bars

Saint Petersburg State University of Architecture and Civil Engineering, 4 Vtoraya Krasnoarmeiskaya, 190005, Saint Petersburg, Russia

^* Corresponding author: mstefania@mail.ru

Abstract

The aim of the research is to study the shear strength of laminated veneer lumber (LVL) when working on shear in four different planes. To determine the influence of the presence of technological cracks formed in the peeling process, an experiment was carried out for which four types of samples were used. The load was applied parallel and perpendicular to the glue line and the direction of the peeled veneer fibers. As tests have shown, the technological weakening of peeled veneer reduces the strength properties of a multilayer glued veneer bar, especially for shear along the glue lines and perpendicular to the direction of the peeled veneer fibers, where the maximum number of microcracks is located. The analysis of these microcracks is carried out and their widths are determined. The width of the studied cracks was from 152 to 94 μm. There is no adhesive layer in the microcracks of this building material, which may indicate insufficient wetting of the veneer surface with the adhesive material, or the difficulty of penetration of high-molecular phenol-formaldehyde glue into the cavity of microcracks.