PLYWOOD


Meaning of PLYWOOD in English

composite wood panel made of three or more layers glued together with the grain of adjoining plies at right angles to each other. Thin panels are built up of veneer (thin sheet wood) exclusively. For thicker panels, sawed lumber often is used as the centre ply, or core, the product being called lumber-core plywood. Two types of plywood are made: interior plywood, for use only in dry locations, and exterior plywood, for which water-resistant glues are used. Wherever a material is required to cover large areas with a light but strong and rigid sheeting, plywood may be used; for example, in cabinetmaking, for chests, dressers, wardrobes, and tables; in housebuilding, for walls, ceilings, floors, doors, cupboards, and cement forms; in coachbuilding, for trucks, vans, and trailers; in shipbuilding, for small boat hulls, decks, and cabins; and in boxmaking, for shipping and storage chests and cases. Plywood has a number of advantages over solid wood: it can be manufactured into large sheets with few defects; it is stronger than boards of the same thickness; shrinking and swelling are almost eliminated because the plies cross each other; splitting in handling and nailing is greatly reduced; and wood of lower grades can be used for the interior plies. Since veneer can be dried in a few minutes, dry plywood can be produced from green logs in a day. Plywood is almost always composed of an odd number of plies so that the grain of corresponding plies, counting from the outside in, runs in the same direction, balancing and stabilizing the construction. Veneer used for plywood usually varies in thickness from 1/28 to 1/8 inch (0.09 to 0.32 centimetres), but both thinner and thicker veneers often are used. Thin veneers have an advantage, especially for the outer, or face, plies, in that they set up less severe transverse stresses with changes in moisture content, thereby reducing warping and surface checking (superficial cracking) of panels. The use of thin veneer also makes valuable wood go farther. Since successively cut layers of thin veneers are similar in appearance, identical areas from adjacent sheets can be matched to make highly symmetrical ornamental patterns. In lumber-core panels, the plies next to the faces or the crossbands usually are thicker than the face plies and largely control the stability of the panel. In sandwich construction, thin facings are bonded on a thick core. The facings are made of strong material, such as thin, dense plywood, and the core of a lightweight material, such as balsa wood, cellular cellulose acetate, or paper honeycomb. The core serves primarily to separate and stabilize the thin faces, which are the principal load-carrying portions. The complete assembly is exceedingly strong and stiff for its weight.

Britannica English vocabulary.      Английский словарь Британика.