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plywood
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What is plywood?
Plywood is a structural material made by gluing thin sheets of wood (veneers or plies) together. The grain of each layer is typically arranged at right angles to increase its strength and resistance to splitting. This panel product is favored for its dimensional stability, which means it doesn't change size much with temperature and humidity changes.
Plywood is made by spreading glue on the veneers and assembling them so that the grain direction alternates between layers. The outer layers are the face and back, the inner layer is the core, and the layers between are crossbands. It is used in floors, roofs, walls, decorative trim, cabinets, and shipbuilding.
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How is plywood different from regular wood?
Plywood is a structural material made by gluing thin sheets of wood (veneers or plies) together, typically with the grain of the layers arranged at perpendicular angles. This gives plywood advantages over regular wood, such as:
- Dimensional stability Plywood is less prone to changes in dimension due to temperature and humidity.
- Resistance to splitting The cross-grain construction enhances resistance to splitting and warping.
- Uniformity of strength Distributes strength evenly across the panel.
Plywood is produced in flat sheets and can be manufactured in curved shapes. It is used in environments prone to atmospheric changes or exposure to moisture, as well as for decorative purposes, such as in cabinetry and furniture.
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How is plywood made?
Plywood is a composite wood made by gluing layers of wood veneer together. The process involves matching the thickness and grain of each veneer to a counterpart on the opposite side of a central layer, resulting in an odd number of layers. The layers, called the face, back, core, and crossbands, are assembled with the grain direction varying between them.
The assembled panels are then loaded into heated presses to activate thermoset adhesives like phenol-formaldehyde and urea-formaldehyde. These resins bond the layers, creating a product stronger and more durable than natural wood. After pressing, the panels cool, and are sanded, graded, and stored.
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What are the layers in plywood called and why are they glued at angles?
Plywood layers consist of the face and back (outer layers), the core (inner layer), and crossbands (layers between). Standard construction involves crossbands running perpendicular to the face, back, and core, but in some instances, alternating plies are placed at 45-degree angles.
Plywood is constructed by gluing layers of wood (veneers) together, with the grain of each layer oriented at right angles to the grain of adjacent layers. This cross-graining improves strength and reduces the risk of warping and splitting, providing dimensional stability and uniformity of strength.
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What are some common uses of plywood?
Plywood is a composite material made by gluing thin wood sheets (veneers or plies) together, with the grain of each layer typically arranged at right angles for strength. This gives plywood advantages such as dimensional stability and resistance to splitting.
Common uses of plywood include:
* Building construction (walls, floors, roofs, doors)
* Exterior siding and interior finishing (wall paneling)
* Furniture and shelving
* Shipbuilding
* Automobile manufacture
* Concrete formwork
* Fencing
* Toys
* Decorative trim
* Cabinets2 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How does plywood compare to other types of composite wood, like particleboard or MDF?
Plywood, particleboard, and fibreboard are panel products made from wood-based materials and adhesives. Plywood is made by gluing thin sheets of wood (veneers or plies) together, with the grain of each layer typically arranged at right angles. This gives it greater dimensional stability and resistance to splitting compared to natural wood.
Particleboard consists of wood particles glued together and can be single-layer, three-layer, or graded. Fibreboard is made of wood fibres and may or may not use a resin adhesive. Medium-density fibreboard (MDF) is a type of fibreboard that can be machined like solid wood. Unlike plywood, particleboard and fibreboard utilize wood residues and wood of low quality.
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plywood, structural material manufactured by gluing together thin sheets of wood, called veneers or plies, with the grain of the layers typically arranged at wide or perpendicular angles for strength. Plywood is a panel product, like particleboard and fibreboard, meaning it is produced in flat sheets from wood-based materials and adhesive.
Plywood has several advantages over natural wood, especially its dimensional stability (the measure of how much a material’s dimensions change due to temperature and humidity) and resistance to splitting. For these reasons, it is one of the most important wood products because wood is often used in environments prone to atmospheric changes or exposure to moisture. Plywood is also used for decorative purposes, particularly in cabinetry and furniture. It can be manufactured in curved shapes, called molded plywood, in which the veneers are bent and shaped as they are glued together. Typically, plywood panels range in thickness from 3 mm (about 0.12 inch) for all-veneer plywood to as much as 30 mm (1.2 inches) for lumber-core materials.
Laminated wood, in contrast, is a plywoodlike product in which multiple veneers are glued together with their grains in parallel, losing much of the strength of plywood but retaining advantages over lumber in stiffness, tensile strength, and compressive strength. Laminated wood is usually considered distinct from plywood, though the two are closely related.
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History
The history of plywood can be traced back to ancient Egypt, where layers of veneer in contrasting colours of wood were spread with glue and pressed together with sandbags. Ancient Egyptian furniture has been recovered with layers of wood combined with metals, ivory, and precious stones. Using veneers, particularly beautiful or valuable wood could be sliced very thin and applied to less valuable wood to improve its appearance. The technique of using veneers to beautify wooden objects was generally reserved for the wealthy because the veneers had to be cut by hand.
The invention of powered tools allowed for the widespread production of veneers and also enabled plywood to become a cost-effective material for everyday furniture by the late 19th century. With the advent of the use of resin adhesives in the 1930s, particularly phenol-formaldehyde and urea-formaldehyde resins, the use of plywood increased, and it became a ubiquitous construction material. Since the mid-20th century, plywood has been used in the construction of floors, roofs, and walls. It is used for decorative trim, wall paneling, cabinets, shelving, and exterior siding. Outside of the home, it is used in fencing, automobile interiors, the construction of boats and ships, and many other applications.
Production
The process of creating plywood is complex and can vary widely depending on the product. In some products, plywood is produced with a lumber core, but all-veneer plywood is much more common. In either case, the thickness and grain orientation of each veneer is matched with a veneer on the other side of the central piece, resulting in an odd number of layers. Occasionally, the central layer may consist of two veneers glued together with parallel grain directions, resulting in an even number of layers. Its resistance to warping and splintering and its uniformity of strength is increased by varying the orientation of the grain.
The panels are spread with glue and assembled such that the direction of the grain varies between layers. The outer layers are called the face and the back, the inner layer is called the core, and the layers between are called crossbands. In standard construction, the crossbands run perpendicular to the face, back, and core, allowing for maximum strength and stability. In some cases, alternating plies may be placed at 45-degree angles. The stacked plies are then loaded into presses.
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In general, the presses are large powered devices that are heated to activate the adhesives, which are typically thermoset (that is, permanently set) synthetic resins such as phenol-formaldehyde and urea-formaldehyde. These are polymers that cannot be reshaped after they are cooled. These resins bond the layers of veneer into a product that can be stronger than natural wood and more durable to the elements, from seawater to microorganisms to dry heat.