Plywood is an engineered wood, it is a sheet material manufactured from thin layers or "plies" of wood veneer that are glued together with adjacent layers having their wood grain rotated up to 90 degrees to one another (sandwich) making it highly resistant due to the way the plies are layered.
Each layer of wood, or ply, is usually oriented with its grain running at right angles to the adjacent layer in order to reduce the shrinkage and improve the strength of the finished piece. Most plywood is pressed into large, flat sheets used in building construction. Other plywood pieces may be formed into simple or compound curves for use in furniture, boats, and aircraft.
All plywood bind resin and wood fiber sheets (cellulose cells are long, strong and thin) to form a composite material. This alternation of the grain is called cross-graining and has several important benefits: it reduces the tendency of wood to split when nailed at the edges; it reduces expansion and shrinkage, providing improved dimensional stability; and it makes the strength of the panel consistent across all directions. A typical plywood panel with wood veneer finish has face veneers of a higher grade than the core veneers.
Plywood panels may be made from hardwoods, softwoods, or a combination of the two.
The most commonly used wood species for plywood panels are:
PLYWOOD VS. MDF (Differences & Properties)
CLASSIFICATION AND GRADING
There are two broad classes of plywood, each with its own grading system.
One class is known as hardwood and decorative. Plywoods in this class are used primarily for their appearance and are graded in descending order of resistance to moisture as Technical (Exterior), Type I (Exterior), Type II (Interior), and Type III (Interior). Their face veneers are virtually free of defects.
The other class of plywood is known as construction and industrial: Plywoods in this class are used primarily for their strength and are rated by their exposure capability and the grade of veneer used on the face and back. Exposure capability may be interior or exterior, depending on the type of glue. Veneer grades may be N, A, B, C, or D. N grade has very few surface defects, while D grade may have numerous knots and splits.
|Thickness (mm)||3 - 40||Finish||Poplar|
|Length x Width (mm)||3050 x 1300||Ilomba|
|3100 x 1530||Birch|
|2440 x 1220||Eucalyptus|
|2500 x 1220||HPL|
|Special Grades||Fire Resistant||Quality||Interior|