Plywood is a common building material. You might picture plywood as being large sheets of thin layers of wood. This is technically accurate, but plywood can be fairly complex material with several different types available. These vary in areas like types of wood, strength and possible applications.
Introduction to Plywood
Plywood is made up of several thin sheets of wood pressed together. These thin sheets are called veneers or plies. The veneers are stacked and glued together in groups of anywhere from three to seven. The grains of the wood change direction with every sheet so the grain on one layer runs perpendicular to the grain of the adjacent layers. This makes the plywood inflexible as the grains act on each other to increase tensile strength. Plywood is also graded using grades like A, the highest quality, A/B, a high quality front with a slightly lower quality back, and X, the lowest quality with several defects on the plywood surface.
Soft plywood is usually made of wood from trees like Douglas firs, pines and cedars. There is no standard thickness for a veneer, but the total thickness of a piece of soft plywood can vary from 5/8 of an inch to 1 inch. These plywoods are used primarily in building and construction. They are commonly parts of fences, floors, walls and roofs. Soft plywood can even be used as part of a vehicle's interior or to manufacture shipping containers.
Hard plywood is typically made from either maple, birch or a mixture of wood from tropical regions like Malaysia or other parts of Southeast Asia. Tropical plywood is traditionally the only type that uses different kinds of wood in a single sheet of plywood. Due to the added strength of these plywoods over the softer types, they are useful in more heavy-duty construction. Scaffolding, high-impact floors, furniture, sports equipment, musical instruments and even wind turbine blades can be made out of these more durable plywoods.
There are several other types of plywood designed for more specific uses. There is aircraft plywood which is similar to birch plywood except it uses special adhesives to bind the plies. This gives it added resistance to the heat and humidity that can affect airplanes. Marine plywood is a special type of plywood treated to withstand wet and humid environments. This material is used in building various docks or boats. There is also a flexible type of plywood, sometimes called "bendy board," that can be bent and applied to curved surfaces.
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