Flexural and shear properties of fiber-reinforced plywood

Fiber-reinforced plywoods composed of veneer and graphite fiber cloth of different inserted forms and positions were manufactured and their mechanical properties were investigated. The effects of reinforcing insert orientations and positions on the flexural and shear properties of the reinforced plywoods are discussed. Inserting the fiber cloth with 0 degrees or 90 degrees orientations near both surfaces was very advantageous for flexural strength and stiffness of the reinforced plywood, whereas the 45 degrees orientation only improved its strength. However, with respect to the shear moduli, inserting the fiber cloth in the 45 degrees orientation clearly was superior to inserting it at 0 degrees or 90 degrees. The panel shear modulus depends on the reinforcement orientation but not on the positions of the reinforcing layers, whereas the plate shear modulus is related to both orientation and position. Reinforcing layers are placed most advantageously on or near both surfaces for improving the plate shear modulus. When we design fiber-reinforced veneer composites for use in wood construction, the reinforcement method in which the fiber cloth is inserted in gluelines near both surfaces in the 45 degrees orientation will be advantageous for greatly enhancing flexural strength and shear rigidity while retaining the wooden faces of the fiber-reinforced composite.