Plywood is a material manufactured from thin layers or "plies" of wood veneer that are glued together with adjacent layers having their wood grain rotated up to 90 degrees to one another. It is an engineered wood from the family of manufactured boards which includes medium-density fibreboard and particle board. All plywoods bind wood fibre sheets to form a composite material; this alternation of the grain is called cross-graining and has several important benefits: it reduces the tendency of wood to split when nailed at the edges. There is an odd number of plies, so that the sheet is balanced—this reduces warping; because plywood is bonded with grains running against one another and with an odd number of composite parts, it has high stiffness perpendicular to the grain direction of the surface ply. Smaller and lower quality plywoods may only have their plies arranged at right angles to each other; some better-quality plywood products will by design have five plies in steps of 45 degrees, giving strength in multiple axes.

The word ply derives from the French verb plier, "to fold", from the Latin verb plico, from the ancient Greek verb πλέκω. The ancient Egyptians and Greeks cut wood thinly and glued it together in layers with the grain in perpendicular directions, making a versatile building material. In 1797 Samuel Bentham applied for patents covering several machines to produce veneers. In his patent applications, 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. Bentham was a British naval engineer with many shipbuilding inventions to his credit. Veneers at the time of Bentham were rift sawn or quarter sawn. About fifty years Immanuel Nobel, father of Alfred Nobel, realized that several thinner layers of wood bonded together would be stronger than a single thick layer of wood. Understanding the industrial potential of laminated wood, he invented the rotary lathe. There is little record of the early implementation of the rotary lathe and the subsequent commercialization of plywood as we know it today, but in its 1870 edition, the French dictionary Robert describes the process of rotary lathe veneer manufacturing in its entry Déroulage.

One can thus presume that rotary lathe plywood manufacturer was an established process in France in the 1860s. Plywood was introduced into the United States in 1865 and industrial production started shortly after. In 1928, the first standard-sized 4 ft by 8 ft plywood sheets were introduced in the United States for use as a general building material. Artists use plywood as a support for easel paintings to replace traditional cardboard. Ready-made artist boards for oil painting in three-layered plywood were produced and sold in New York as early as 1880. A typical plywood panel has face veneers of a higher grade than the core veneers; the principal function of the core layers is to increase the separation between the outer layers where the bending stresses are highest, thus increasing the panel's resistance to bending. As a result, thicker panels can span greater distances under the same loads. In bending, the maximum stress occurs in the outermost layers, one in tension, the other in compression.

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, at the outer fibres. Within Europe basic plywood can be divided into three main categories: birch plywood, mixed plywood and conifer plywoods. Different varieties of plywood exist for different applications: Softwood plywood is made either of cedar, Douglas fir or spruce and fir or redwood and is used for construction and industrial purposes; the most common dimension is 1.2 by 2.4 metres or the larger imperial dimension of 4 feet × 8 feet. Plies vary in thickness from 1.4 mm to 4.3 mm. The number of plies --, always odd -- depends on the grade of the sheet. Roofing can use the thinner 5⁄8-inch plywood. Subfloors are at least 3⁄4 inch thick, the thickness depending on the distance between floor joists. Plywood for flooring applications is tongue and groove. T&G plywood is found in the 1⁄2-to-1-inch range. Hardwood plywood is used for demanding end uses.

Hardwood plywood is characterized by its excellent strength and resistance to creep. It has a high planar shear strength and impact resistance, which make it suitable for heavy-duty floor and wall structures. Oriented plywood construction has a high wheel-carrying capacity. Hardwood plywood has excellent surface hardness, damage- and wear-resistance. Tropical plywood is made of mixed species of tropical timber. From the Asian region, it is now manufactured in African and South American countries. Tropical plywood is superior to softwood plywood due to its density, evenness of layers, high quality, it is sold at a premium in many markets if manufactured with high standards. Tropical plywo

David H. Helms

David H. Helms was a Union Army soldier during the American Civil War, he received the Medal of Honor for gallantry during the Siege of Vicksburg on May 22, 1863. Helms joined the army from Indiana in August 1862, was discharged in June 1865. On May 22, 1863, General Ulysses S. Grant ordered an assault on the Confederate heights at Vicksburg, Mississippi; the plan called for a storming party of volunteers to build a bridge across a moat and plant scaling ladders against the enemy embankment in advance of the main attack. The volunteers knew the odds were against survival and the mission was called, in nineteenth century vernacular, a "forlorn hope". Only single men were accepted as volunteers and then, twice as many men as needed came forward and were turned away; the assault began in the early morning following a naval bombardment. The Union soldiers came under enemy fire and were pinned down in the ditch they were to cross. Despite repeated attacks by the main Union body, the men of the forlorn hope were unable to retreat until nightfall.

Of the 150 men in the storming party, nearly half were killed. Seventy-nine of the survivors were awarded the Medal of Honor. “For gallantry in the charge of the volunteer storming party on 22 May 1863.” List of American Civil War Medal of Honor recipients: G-L "David H. Helms". Hall of Valor. Military Times. David H. Helms at Find a Grave A Forlorn Hope Vicksburg Medal of Honor Recipients

Michel Lugo

Michel Antunes Lugo is a Brazilian footballer who plays for Hong Kong Premier League club Tai Po. After playing for a number of clubs in Brazil, Lugo signed for Paços de Ferreira of Primeira Liga in 2011. In the following two seasons, he went back home and played for GE Bagé and União Frederiquense, before signing for Sun Hei in Hong Kong on a free transfer, he made his debut for the club in a 6–2 away defeat against Kitchee, where he scored a goal in the 44th minute. On 31 July 2018, Tai Po announced the signing of Lugo. Tai PoHong Kong Premier League: 2018–19 Michel Lugo at ForaDeJogo Michel Lugo at Soccerway