Possibility of making flexible three-ply plywood using poplar (Populus deltoides) and Paulownia (Paulownia fortunei) veneers

In this research, the feasibility of producing flexible plywood employing combinations of poplar (Populus deltoides) and Paulownia (Paulownia fortunei) veneers with thickness of 1 and 2 mm was investigated. For this aim, layer combinations, treatment type, and the resin type were chosen as variables. Laboratory panels were produced based on Taguchi design of experiments (L18;6^1 3^2) and some physical and mechanical properties of the specimens including density, moisture content, water absorption and thickness swelling after 24 h of immersion in water, modulus of rupture and modulus of elasticity parallel and perpendicular to the grain, bonding quality, and bending radius were determined. The present work focuses on using Taguchi method in order to detect the optimum combination of the parameters. The results revealed that bending radius was considerably influenced by the properties of wood and the thickness of the core veneer. The outcomes showed that as the thickness of the core veneer decreased, the bending radius increased. Accordingly, the optimum choice for the core layer of plywood is poplar with a thickness of 1 mm, and the best elastic attributes were obtained for plywood with veneers treated by the Pro-Glu solution. Polyvinyl acetate also demonstrated an increase in flexibility, and a decrease in MOE. The experimental samples of the manufactured plywood could ultimately bend around a cylinder with a diameter of 6.5 mm to reach the minimum bending radius with no sign of damage.