How Plywood Is Made

Symmetry principle: The veneer on both sides of the symmetrical central plane, regardless of the thickness of the veneer, the number of layers, the manufacturing method, the fiber direction and the moisture content of the veneer, should correspond to each other, that is, the symmetrical principle of the plywood on both sides of the central plane. The corresponding layers are in different directions. The stress is equal in magnitude. Therefore, when the moisture content of plywood changes, its structure is not disordered, and there will be no defects such as deformation and cracking; on the contrary, if there are some differences in the corresponding layers on both sides of the symmetrical central plane, the stress of the veneer on both sides of the symmetrical central plane will be caused. If they are not equal, the plywood will be deformed and cracked.

Odd-numbered layer principle: Because the structure of plywood is that the fiber directions of adjacent layers of veneers are perpendicular to each other, and must comply with the principle of symmetry, its total number of layers must be an odd number. Such as: three-layer board, five-layer board, seven-layer board, etc. When the odd-numbered plywood is bent, the maximum horizontal shear stress acts on the central veneer, making it stronger. When the even-numbered plywood is bent, the maximum horizontal shear stress acts on the adhesive layer instead of the veneer, which is easy to damage the adhesive layer and reduce the strength of the plywood.