Plywood
1) define
Plywood shuttering sheets is log along the direction of the growth ring rotary cut into a large veneer, after drying, coated with glue according to the direction of the adjacent veneer layer of wood grain perpendicular to the principle of group blank, gluing and become the board.The number of veneer layers is odd, usually three to thirteen layers, common plywood, five-ply, nine plywood, and thirteen ply for shuttering (commonly known in the market as three board, five board, nine board, thirteen board).The outermost front panel is called the panel, the back panel is called the backplane, and the inner layer is called the core board.
2) classification
One kind of century shuttering plywood is weather-resistant and boiling water-resistant plywood, which has the advantages of durability construction plywood home depot, high temperature resistance and steam treatment.
The second type plywood is water-resistant plywood, which can be impregnated in cold water and hot water for a short time.
The third type of plywood is plywood formed concrete, which can be impregnated in cold water for a short time and is suitable for indoor use at room temperature.plywood used for formwork and general building purposes;
4 kinds of plywood is not be able to bear tide construction shuttering plywood, use below indoor normal state, formwork plywood price of general use has beech, basswood, ash, birch, elm, poplar with material.
3) Constitution principle
Principle of symmetry: cost of shuttering ply veneer on both sides of symmetrical central plane, regardless of veneer thickness, layer number, manufacturing method, fiber direction and water content of veneer should correspond to each other, that is, the magnitude of stress in different directions of each corresponding layer on both sides of symmetrical central plane of selco shuttering ply should be equal.Therefore, when the moisture content of ply shuttering concrete changes, its structure is stable, will not produce deformation, cracking and other defects;On the contrary, if there are some differences between the corresponding layers on both sides of the symmetric center plane, the stress of the veneer on both sides of the symmetric center plane is not equal, so that the plywood will be deformed and cracked.
Odd number of layers principle: because the structure price of shutter ply board is the fiber direction of adjacent layers of veneer perpendicular to each other, and must conform to the principle of symmetry, so its total number of layers must be odd.Such as: three layer board, five layer board, seven layer board and so on.When odd-numbered plywood is bent, the maximum horizontal shear stress acts on the central veneer, which makes it have greater strength.The maximum horizontal shear stress in the bending of even layers of brown film faced plywood acts on the adhesive layer rather than on the veneer, which is easy to destroy the adhesive layer and reduce the strength of ply formwork with logo.
3, decorative panel
Acting the role of the face plate is called decorative veneer plywood, it is natural wood or science and technology wood planer cut into a certain thickness of the slice, adhere to the plywood surface, and then hot pressing and become a kind of surface materials for indoor decoration or furniture manufacturing.Common act the role of face plate cent is natural woodiness veneer act the role of face plate and man-made thin wood act the role of face plate.The appearance difference between artificial veneer and natural wood veneer is that the texture of the former is basically straight texture or pattern has rules;And the latter is natural woodiness pattern, grain pattern is natural, variability is larger, irregular.Its characteristics: it not only has the beautiful pattern of wood, but also achieves the full use of wood resources and reduces the cost.
