Plywood construction type

Plywood construction refers to the composition of the inner plies or layers. The faces are usually always veneer but the cores may consist of four different types of wood materials all inner plies of (1) wood veneer ... 

Some report that over 50 percent of the urea-formaldehyde resins consumed went into particleboard. This is brought out because there may be a shift away from urea resin for certain types of oriented particleboard used in structural plywood constructions. Historically, particleboard has been used for inner plies as previously mentioned in some hardwood plywood. There is now one plant in production in Idaho which produces mechanically oriented strand particleboard for use specifically as core for softwood plywood production. It is anticipated that this trend to some degree will increase in the future, and phenolic resins appear to be the mechanism with which this particleboard will be bonded. 

Formaldehyde emission and/or formaldehyde space level potential can be related to both construction type and product end use. While the American National Standard for Hardwood and Decorative Plywood (1 ) references eight different types of construction, three are most important in the context of formaldehyde ... 

Solid. Usually of plywood, this type of construction provides great strength as well as a smooth interior surface. 

Below-grade walls may be constructed of poured concrete, masonry blocks, or other materials such as all-weather wood or stone. This chapter discusses details for use of poured concrete and masonry foundation because these are the materials most commonly used for new construction. Recently, trade associations such as American Plywood Association (APA) and the National Forest Products Association (NFoPA) have issued publications on designing radon resistance permanent wood foundations. Information on these types of foundations can be found by contacting the appropriate trade association.21... 

Softwood plywood is usually used for construction application and is the type commonly found in local lumber and home center stores. The face plies are generally fir. Shipments in 1989 were estimated at 5.02 billion. The Pacific Northwest represented 42% of the total whereas 36% came from the South. 

Thin hardwood plywood in the range of 4.5—6.0 mm (3/16—1 /4 in.) was normally a three-ply construction with a thin, medium-quality back ply, a thicker lower value core, and another thin, high quality decorative face veneer. These panels were used as wall paneling, door facings, or for fumiture/cabinet applications requiting thin panels. Currently, only relatively small quantities of these types of panels are produced in the United States. 

The types of adhesives suitable for laminating beams are restricted by the conditions of application and by their end-use requirements. A wider choice of adhesives for plywood depends on whether softwoods or hardwoods are used, whether they are required for internal or external exposures, or whether they are to be used for ornamental or structural purposes. Thus phenol-formaldehyde types would be used for marine or exterior construction uses urea-formaldehyde types would be advantageous for cold pressing, or melamine-urea adhesives might be preferred for hardwood plywood, or lumber-core panels used in furniture production. 

Test Method for Strength Properties of Adhesives in Plywood Type Construction in Shear by Tension Loading Terminology of Adhesives... 

Traditionally plywood has required a much higher grade of log than was necessary for the manufacture of other wood panels, so those nations with an unsuitable wood supply have had to import plywood although now there are manufacturing construction grades that use a poorer and smaller log type. 

Traditionally, UF, MUF and PF adhesives have been the preferred adhesive systems for production of plywood worldwide. In the European market these adhesive types are still predominant. There are, however, a few producers using EPI adhesives for products where metal is included in the construction. 

The possibilities for making bonded structural sandwich elements in a variety of materials are very real. However, whilst there exist structural examples such as aluminium honeycomb panels (used in aircraft and transport applications) and metal skinned foam sandwich panels (used as the monocoque chassis in refrigerated transport applications), these composite constructions are normally utilised in non- or semi-structural ways. Typical skin materials are steel, aluminium, GRP and plywood, and common core materials are rigid foam polystyrene, polyurethane, polyisocyanurate, PVC, and honeycombed aluminium. In some instances the foam core is injected between the skins and adheres to them in others, adhesives are used to bond the separate components together. The nature of the manufaeturing process depends on the type of structure to be made, and the degree of investment in produetion maehinery. Both flat and eomplex eurved forms ean be made by a hand lay-up process as well as in an automated way. 

ASTM D906-98 Standard test method for strength properties of adhesives in plywood type construction in shear by tension loading. 

The range of wood-based boards, and the applications in which they are used, is large, and increasing. Examples are the use of plywood in structural situations, such as I-beams or box beams, on the one hand, to the construction of short-Uved products, such as coffins from veneered particle board. Not all types of wood-based boards are suitable for aU uses. 

To overcome these problems a similar construction was used but with 0.91 mm aluminium skins instead of plywood - Boeing 707, Douglas DC 6 and DC 9 (the DC 9 still uses this type of construction). However, the skins were still vulnerable to damage in areas between the stringers, especially from castor wheels of catering trolleys. 

D-0906. Test Method for Strength Properties of Adhesives in Plywood Type Construction in Shear by Tension Loading. Fig. 7 shows the specimen for this widely used test. In common usage, the main test criterion is a visual estimate of the area percentage of rupture failure which occurs as wood failure (versus glue failure ) and not the measured joint strength. 

Flush doors are produced by bonding skins of plywood, hardboard, or particle board to the vertical and horizontal frames (the stiles and rails), which are usually either a soft wood such as fir or a man-made product comprising layers of pressed board. Hollow core doors utilize an accordion-type paper core, while a solid core door is constructed with a core of pieces of scrap wood edge-glued with an inexpensive casein-soy glue. Some of these cores are held to shape by corrugated cardboard, which is bonded to their surfaces with the same type of protein blend glue. 

Construction plywood is primarily phenolic bonded for an exterior rating. Decorative plywood is primarily bonded with UF resins for interior applications such as wall panels and hardwood flooring tiles. Both types of plywood are composed of layers of veneer or wood with alternating grain orientations that are bonded with heat and pressure. 

In today s construction, flat surfaces may involve plastic laminate, cultured marble, or acrylic countertop. Formerly, most of these products were installed on plywood. Today, however, various types of hardboard, particle board, or wafer board provide suitable substrates. 

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