Softwood plywood made from spruce.PlywoodFrom Wikipedia, the free encyclopediaPlywood is a sheet material manufactured from thin layersor "plies" of wood veneer that are glued together withadjacent layers having their wood grain rotated up to 90degrees to one another. It is an engineered wood from thefamily of manufactured boards which includes medium-density fibreboard (MDF) and particle board (chipboard).All plywoods bind resin and wood fibre sheets (cellulosecells are long, strong and thin) to form a composite material.This alternation of the grain is called cross-graining and hasseveral important benefits: it reduces the tendency of woodto split when nailed at the edges; it reduces expansion andshrinkage, providing improved dimensional stability; and itmakes the strength of the panel consistent across alldirections. There are usually an odd number of plies, so thatthe sheet is balancedthis reduces warping. Because plywood is bonded with grains running against oneanother and with an odd number of composite parts, it is very hard to bend it perpendicular to the grain directionof the surface ply.Smaller thinner plywoods and lower quality plywoods (see Average-quality plywood photo below and right) mayonly have their plies (layers) arranged at right angles to each other, though some better quality plywoodproducts will by design have five plies in steps of 45 degrees (0, 45, 90, 135, and 180 degrees), giving strength inmultiple axes.Contents1 History2 Structural characteristics3 Types3.1 Softwood plywood3.2 Hardwood plywood3.3 Tropical plywood3.4 Aircraft plywood3.5 Decorative plywood (overlaid plywood)3.6 Flexible plywood3.7 Marine plywood3.8 Other plywoods4 Production5 Sizes6 Grades7 Applications7.1 Softwood plywood applications7.2 Hardwood plywood applications7.3 Tropical plywood applicationsPlywood - Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Plywood1 of 9 8/11/2015 3:50 PM8 See also9 References10 External linksHistoryIn 1797 Samuel Bentham applied for patents covering several machines to produce veneers. In his patentapplications, he described the concept of laminating several layers of veneer with glue to form a thicker piece the first description of what we now call plywood.[1] Samuel Bentham was a British naval engineer with manyshipbuilding inventions to his credit. Veneers at the time of Bentham were flat sawn, rift sawn or quarter sawn;i.e. cut along or across the log manually in different angles to the grain and thus limited in width and length.About fifty years later Immanuel Nobel, father of Alfred Nobel, realized that several thinner layers of woodbonded together would be stronger than one single thick layer of wood ; understanding the industrial potential oflaminated wood he invented the rotary lathe.There is little record of the early implementation of the rotary lathe and the subsequent commercialization ofplywood as we know it today, but in its 1870 edition, the French dictionary Robert describes the process ofrotary lathe veneer manufacturing in its entry Droulage.[2] One can thus presume that rotary lathe plywoodmanufacture was an established process in France in the 1860s. Plywood was introduced into the United Statesin 1865[3] and industrial production started shortly after. In 1928, the first standard-sized 4 ft by 8 ft (1.2 m by2.4 m) plywood sheets were introduced in the United States for use as a general building material.[1]Artists use plywood as a support for easel paintings to replace traditional canvas or cardboard. Ready-madeartist boards for oil painting in three-layered plywood (3-ply) were produced and sold in New York as early as1880.[4]Structural characteristicsA typical plywood panel has face veneers of a higher grade than the core veneers. The principal function of thecore layers is to increase the separation between the outer layers where the bending stresses are highest, thusincreasing the panel's resistance to bending. As a result, thicker panels can span greater distances under thesame loads. In bending, the maximum stress occurs in the outermost layers, one in tension, the other incompression. Bending stress decreases from the maximum at the face layers to nearly zero at the central layer.Shear stress, by contrast, is higher in the center of the panel, and zero at the outer fibres.TypesDifferent varieties of plywood exist for different applications:Softwood plywoodSoftwood panel is usually made either of cedar, Douglas fir or spruce, pine, and fir (collectively known asspruce-pine-fir or SPF) or redwood and is typically used for construction and industrial purposes.[5]The most common dimension is 1.2 by 2.4 metres (3 ft 11 in 7 ft 10 in) or the slightly larger imperialPlywood - Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Plywood2 of 9 8/11/2015 3:50 PMAverage-quality plywood with 'showveneer'High-quality concrete pouring plate inplywoodBirch plywooddimension of 4 feet 8 feet. Plies vary in thickness from 1.4 mm to4.3 mm. The number of plies depends on the thickness and grade of thesheet but at least three are required as the minimum odd number of plies.Roofing can use the thinner 5/8" (15 mm) plywood. Subfloors are at least3/4" (18 mm) thick, the thickness depending on the distance betweenfloor joists. Plywood for flooring applications is often tongue and groove;This prevents one board from moving up or down relative to its neighbor,so providing a solid feeling floor when the joints do not lie over joists.T&G plywood is usually found in the 1/2" to 1" (1225 mm) range.Hardwood plywoodHardwood plywood is made out of wood from angiosperm trees and usedfor demanding end uses. Hardwood plywood is characterized by itsexcellent strength, stiffness and resistance to creep. It has a high planarshear strength and impact resistance, which make it especially suitablefor heavy-duty floor and wall structures. Oriented plywood constructionhas a high wheel-carrying capacity. Hardwood plywood has excellentsurface hardness, and damage- and wear-resistance.[6]Tropical plywoodTropical plywood is made of mixed species of tropical wood. Originallyfrom the Asian region, it is now also manufactured in African and SouthAmerican countries. Tropical plywood is superior to softwood plywooddue to its density, strength, evenness of layers, and high quality. It isusually sold at a premium in many markets if manufactured with highstandards. Tropical plywood is widely used in the UK, Japan, UnitedStates, Taiwan, Korea, Dubai, and other countries worldwide. It is thepreferred choice for construction purposes in many regions due to its lowcost. However, many countries forests have been over-harvested,including the Philippines, Malaysia and Indonesia, largely due to thedemand for plywood production and export.Aircraft plywoodHigh-strength plywood also known as aircraft plywood, is made from mahogany and/or birch, and usesadhesives with increased resistance to heat and humidity. It was used for several World War II fighter aircraft.Although the British-built Mosquito bomber, nicknamed "The Wooden Wonder", was constructed of a plywoodmonocoque, this was formed in moulds from individual veneers of birch, balsa and birch, rather than machinedfrom pre-laminated plywood sheets.Structural aircraft-grade plywood is more commonly manufactured from African mahogany or American birchveneers that are bonded together in a hot press over hardwood cores of basswood or poplar or from EuropeanBirch veneers throughout . Basswood is another type of aviation-grade plywood that is lighter and more flexiblethan mahogany and birch plywood but has slightly less structural strength. Aviation-grade plywood ismanufactured to a number of specifications including those outlined since 1931 in the Germanischer LloydRules for Surveying and Testing of Plywood for Aircraft and MIL-P-607, the latter of which calls for sheartesting after immersion in boiling water for three hours to verify the adhesive qualities between the plies andPlywood - Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Plywood3 of 9 8/11/2015 3:50 PMmeets specifications.Decorative plywood (overlaid plywood)Usually faced with hardwood, including ash, oak, red oak, birch, maple, mahogany, Philippine mahogany (oftencalled lauan, luan or meranti and having no relation to true mahogany), rose wood, teak and a large number ofother hardwoods. However, Formica, metal and resin-impregnated paper or fabric bonded are also added on topof plywood at both side as a kind of ready for use in the decoration field. This plywood is a lot easier to dye anddraw on than any other plywoods.Flexible plywoodFlexible plywood is very flexible and is designed for making curved parts. In the UK this is sometimes known as"Hatters Ply" as it was used to make stovepipe hats in Victorian times . It is also often referred to as "BendyPly" due to its flexibility. However these may not be termed plywood in some countries because the basicdescription of plywood is layers of veneered wood laid on top of each other with the grain of each layerperpendicular to the grain of the next. In the U.S.A, the terms "Bender Board" and "Wiggle Board" arecommonly used.Marine plywoodMarine plywood is manufactured from durable face and core veneers, with few defects so it performs longer inboth humid and wet conditions and resists delaminating and fungal attack. Its construction is such that it can beused in environments where it is exposed to moisture for long periods. More recently, tropical producers havebecome dominant in the marine plywood market. Okoum from Gabon is now the accepted standard for marineplywood, even though the wood is not very resistant to rot and decay. Each wood veneer will be from tropicalhardwoods, have negligible core gap, limiting the chance of trapping water in the plywood and hence providinga solid and stable glue bond. It uses an exterior Water and Boil Proof (WBP) glue similar to most exteriorplywoods.Marine plywood can be graded as being compliant with BS 1088, which is a British Standard for marineplywood. There are few international standards for grading marine plywood and most of the standards arevoluntary. Some marine plywood has a Lloyd's of London stamp that certifies it to be BS 1088 compliant. Someplywood is also labeled based on the wood used to manufacture it. Examples of this are Okoum or Meranti.Marine plywood is frequently used in the construction of docks and boats. It is much more expensive thanstandard plywood: the cost for a typical 4-foot by 8-foot 1/2-inch thick board is roughly $75 to $100 U.S. oraround $2.50 per square foot, which is about three times as expensive as standard plywood.Other plywoodsOther types of plywoods include fire-retardant, moisture-resistant, wire mesh, sign-grade, and pressure-treated.However, the plywood may be treated with various chemicals to improve the plywood's fireproofing. Each ofthese products is designed to fill a need in industry.ProductionPlywood production requires a good log, called a peeler, which is generally straighter and larger in diameter thanone required for processing into dimensioned lumber by a sawmill. The log is laid horizontally and rotated aboutPlywood - Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Plywood4 of 9 8/11/2015 3:50 PMits long axis while a long blade is pressed into it, causing a thin layer of wood to peel off (much as a continuoussheet of paper from a roll). An adjustable nosebar, which may be solid or a roller, is pressed against the logduring rotation, to create a "gap" for veneer to pass through between the knife and the nosebar. The nosebarpartly compresses the wood as it is peeled; it controls vibration of the peeling knife; and assists in keeping theveneer being peeled to an accurate thickness. In this way the log is peeled into sheets of veneer, which are thencut to the desired oversize dimensions, to allow it to shrink (depending on wood species) when dried. The sheetsare then patched, graded, glued together and then baked in a press at a temperature of at least 140 C (284 F),and at a pressure of up to 1.9 MPa (280 psi) (but more commonly 200 psi) to form the plywood panel. The panelcan then be patched, have minor surface defects such as splits or small knot holes filled, re-sized, sanded orotherwise refinished, depending on the market for which it is intended.Plywood for indoor use generally uses the less expensive urea-formaldehyde glue, which has limited waterresistance, while outdoor and marine-grade plywood are designed to withstand moisture, and use a waterresistant phenol-formaldehyde glue to prevent delamination and to retain strength in high humidity.Anti fungal additives such as Xyligen may sometimes be added to the glueline to provide added resistance tofungal attack.The adhesives used in plywood have become a point of concern. Both urea formaldehyde and phenolformaldehyde are carcinogenic in very high concentrations. As a result, many manufacturers are turning to lowformaldehyde-emitting glue systems, denoted by an "E" rating ("E0" possessing the lowest formaldehydeemissions). Plywood produced to "E0" has effectively zero formaldehyde emissions.[7]In addition to the glues being brought to the forefront, the wood resources themselves are becoming the focus ofmanufacturers, due in part to energy conservation, as well as concern for natural resources. There are severalcertifications available to manufacturers who participate in these programs. Programme for the Endorsement ofForest Certification (PEFC) Forest Stewardship Council (FSC), Leadership in Energy and Environmental Design(LEED), Sustainable Forestry Initiative (SFI), and Greenguard are all certification programs that ensure thatproduction and construction practices are sustainable. Many of these programs offer tax benefits to both themanufacturer and the end user.[8]SizesThe most commonly used thickness range is from 0.14 to 3.0 inches (0.36 to 7.62 cm). The sizes of the mostcommonly used plywood sheets are 4 by 8 feet (1.2 by 2.4 m). Width and length may vary in 1-foot (30 cm)increments.In the United States, the most commonly used size is 4 8 feet (1,200 2,400 mm) or 5 5 feet(1,500 1,500 mm).[9] A common metric size for a sheet of plywood is 1,220 2,440 millimetres(4.00 8.01 ft).Sizes on specialised plywood for concrete-forming can range from 6 to 21 mm (0.24 to 0.83 in), and a multitudeof formats exist, though 157501,500 mm (0.59 inch 2.464.92 ft) is very commonly used.Aircraft plywood is available in thicknesses of 0.4mm (3 ply construction) and upwards, typically Aircraftplywood uses veneers of 0.5mm thickness although much thinner veneers such as 0.1mm are also used inconstruction of some of the thinner panels.GradesPlywood - Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Plywood5 of 9 8/11/2015 3:50 PMGrading rules differ according to the country of origin. Most popular standard is the British Standard (BS) andAmerican Standard (ASTM). Joyce (1970), however, list some general indication of grading rules:[10]Grade DescriptionA Face and back veneers practically free from all defects.A/BFace veneers practically free from all defects. Reverse veneers with only a few small knots ordiscolorations.A/BB Face as A but reverse side permitting jointed veneers, large knots, plugs, etc.B Both side veneers with only a few small knots or discolorations.B/BBFace veneers with only a few small knots or discolorations. Reverse side permitting jointed veneers,large knots, plugs, etc.BB Both sides permitting jointed veneers, large knots, plugs, etc.C/DFor structural plywood, this grade means that the face has knots and defects filled in and the reversemay have some that are not filled. Neither face is an appearance grade, nor are they sanded smooth.This grade is often used for sheathing the surfaces of a building prior to being covered with anotherproduct like flooring, siding, concrete, or roofing materials.WG Guaranteed well glued only. All broken knots plugged.X Knots, knotholes, cracks, and all other defects permitted.JPIC StandardsGrade DescriptionBB/CCFace as BB, back as CC. BB as very little knots of less than 1/4 inches, slight discoloration, no decay,split and wormholes mended skillfully, matched colors, no blister, no wrinkle. Most popular choice formost applications.ApplicationsPlywood is used in many applications that need high-quality, high-strength sheet material. Quality in this contextmeans resistance to cracking, breaking, shrinkage, twisting and warping.Exterior glued plywood is suitable for outdoor use, but because moisture affects the strength of wood, optimalperformance is achieved in end uses where the wood's moisture content remains relatively low. On the otherhand, subzero conditions don't affect plywood's dimensional or strength properties, which makes some specialapplications possible.Plywood is also used as an engineering material for stressed-skin applications. It has been used for marine andaviation applications since WWII. Most notable is the British de Havilland Mosquito bomber, which wasprimarily made using a moulded sandwich of two layers of birch plywood around a balsa core. Plywood wasalso used for the hulls in the hard-chine Motor Torpedo Boats (MTB) and Motor Gun Boats (MGB) built by theBritish Power Boat Company and Vosper's. Plywood is currently successfully used in stressed-skin applications.The American designers Charles and Ray Eames are known for their plywood-based furniture, as is FinnishArchitect Alvar Aalto and his firm Artek, while Phil Bolger has designed a wide range of boats built primarily ofplywood. Jack Kper of Cape Town designed the plywood Dabchick sailing dinghy, which as of 2015 is stillsailed by large numbers of teenagers.Plywood - Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Plywood6 of 9 8/11/2015 3:50 PMPlywood is often used to create curved surfaces because it can easily bend with the grain. Skateboard rampsoften utilize plywood as the top smooth surface over bent curves to create transition that can simulate theshapes of ocean waves.Softwood plywood applicationsTypical end uses of spruce plywood are:Floors, walls and roofs in home constructionsWind bracing panelsVehicle internal body workPackages and boxesFencingThere are coating solutions available that mask the prominent grain structure of spruce plywood. For thesecoated plywoods there are some end uses where reasonable strength is needed but the lightness of spruce is abenefit e.g.:Concrete shuttering panelsReady-to-paint surfaces for constructionsHardwood plywood applicationsPhenolic resin film coated (Film Faced) plywood is typically used as a ready-to-install component e.g.:Panels in concrete form work systemsFloors, walls and roofs in transport vehiclesContainer floorsFloors subjected to heavy wear in various buildings and factoriesScaffolding materials("Wire" or other styles of imprinting available for better traction)Birch plywood is used as a structural material in special applications e.g.:Wind turbine bladesInsulation boxes for liquefied natural gas (LNG) carriersSmooth surface and accurate thickness combined with the durability of the material makes birch plywood afavorable material for many special end uses e.g.:High-end loud speakersDie-cutting boardsSupporting structure for parquetPlayground equipmentFurnitureSigns and fences for demanding outdoor advertisingMusical instrumentsSports equipmentTropical plywood applicationsPlywood - Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Plywood7 of 9 8/11/2015 3:50 PMWikimedia Commons hasmedia related to Plywood.Tropical plywood is widely available from the South-East Asia region, mainly from Malaysia and Indonesia.Tropical plywood boasts premium quality, and strength. Depending on machinery, tropical plywood can be madewith high accuracy in thickness, and is a highly preferable choice in America, Japan, Middle East, Korea, andother regions around the world.Common plywoodConcrete panelFloor baseStructure panelContainer flooringLamin boardLaminated veneer lumber (LVL)See alsoBS 1088Engineered woodFiberboardGlued laminated timberHardboardMasoniteMedium-density fiberboardOriented strand boardParticle boardPressed woodReferences"Plywood" (http://www.answers.com/topic/plywood). Gale's How Products are Made. The Gale Group Inc.Retrieved 26 November 2013.1. "Drouler" (http://historique.fracademic.com/18379d%C3%A9rouler). Le Robert historique de la languefranaise. Dictionnaires Robert. Retrieved 26 November 2013.2. "Plywood" (http://www.answers.com/topic/plywood). Columbia Encyclopedia. Retrieved 26 November 2013. 3. Muller, Norman E. "An early example of a plywood support for painting" (http://www.jstor.org/discover/10.2307/3179496?uid=3738016&uid=2129&uid=2&uid=70&uid=4&sid=21102998036157). Journal of the AmericanInstitute for Conservation. American Institute for Conservation of Historic and Artistic Works. Retrieved26 November 2013.4. O'Halloran, p. 221. 5. Handbook of Finnish plywood, Finnish Forest Industries Federation, 2002, ISBN 952-9506-63-5 [1](http://www.forestindustries.fi/infokortit/handbookplywood/Documents/HandbookOfFinnishPlywood.pdf)6. Engineered Wood Products Association of Australasia (http://www.ewp.asn.au/newsandmedia/downloads/media_release_-_formaldehyde_emissions.pdf). (PDF). Retrieved on 2012-02-10.7. Pro Woodworking Tips.com (http://www.prowoodworkingtips.com/Plywood.html). Pro Woodworking Tips.com.Retrieved on 2012-02-10.8. Metric conversions, Canadian government publication (http://www.cps.gov.on.ca/english/plans/E9000/9011/M-9011L.pdf). (PDF). Retrieved on 2012-02-10.9. Joyce, Ernes. 1970. The Technique of Furniture Making. London: B. T. Batsford Limited. 10. External linksPlywood - Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Plywood8 of 9 8/11/2015 3:50 PMLook up plywood inWiktionary, the freedictionary.APA The Engineered Wood Association(http://www.apawood.org/level_b.cfm?content=prd_ply_main)Material Uses (http://www.prowoodworkingtips.com/Material_Uses_Index.html) Pro Woodworking Tips.comCanadian Plywood Association (http://www.canply.org/english/)Plywood (http://www.technologystudent.com/joints/plywood1.html)Retrieved from "https://en.wikipedia.org/w/index.php?title=Plywood&oldid=675396794"Categories:Plywood Engineered wood Composite materialsThis page was last modified on 10 August 2015, at 09:41.Text is available under the Creative Commons Attribution-ShareAlike License; additional terms mayapply. By using this site, you agree to the Terms of Use and Privacy Policy. 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