Plywood

==Structural characteristics==
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 (physics)|tension]], the other in [[compression (physical)|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, and at the outer fibres. Within Europe basic plywood can be divided into three main categories: birch plywood (density approx. {{val|680|u=kg/m3}}), mixed plywood (density approx. {{val|620|u=kg/m3}}) and conifer plywoods (density 460–{{val|520|u=kg/m3}}).<ref>{{Cite web|url=https://www.woodproducts.fi/content/plywood|title = Front Page}}</ref>