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plywood,manufactured board composed of an odd number of thin sheets of wood glued together under pressure with grains of the successive layers at right angles. Laminated wood differs from plywood in that the grains of its sheets are parallel. Plywood is noted for its strength, durability, lightness, rigidity, and resistance to splitting and warping. It can be molded into curved or irregular forms for use in truck, airplane, and boat bodies, luggage, furniture, and tubing, or it can be made into large panels suitable for structural use. Plywood was made in ancient Egypt and China, and it was first introduced in the United States in 1865. The two types commonly in use today are those made of softwood (fir) or hardwood (birch, mahogany, walnut, or white ash). The layers in inexpensive plywood are glued together with starch pastes, animal glues, or casein, but those of the strongest plywood are glued with waterproof synthetic resins. Other material, such as metal or fabric, may be substituted for the usual wood core.
a wood material consisting of two or more sheets of debarked veneer glued together. Birch veneer is the type most commonly used in plywood production, but alder, beech, pine, and other types may also be used. Plywood is usually built up with from three to five plies, with the grains in adjacent plies arranged to run perpendicular to each other. Both synthetic thermosetting adhesives, such as phenol-formaldehyde and carbamide (urea-formaldehyde) resins, and natural adhesives, such as albumin and casein glues, are used for bonding. Sheets of plywood range in thickness from 1 to 19 mm; the length and width range from 725 to 2,440 mm.
Among the special types of plywood are those classified as resin-impregnated (with improved water resistance), decorative (with a finished exterior veneer), and shaped (formed in a compression mold). Plywood has fairly high longitudinal and transverse mechanical strength, low overall density, and significantly lower anisotropy than natural wood. Plywoods are used extensively in the production of motor vehicles, railroad cars, ships, aircraft, furniture, and containers; they are also used to make cabinets for radio and television sets.
REFERENCEKirillov, A. N., and E. I. Karasev. Proizvodstvo kleenoi fanery. Moscow, 1968.
I. K. CHERKASOV