Wood

Abstract

Wood is a naturally formed organic material consisting essentially of elongated tubular elements called cells arranged in a parallel manner for the most part. These cells vary in dimensions and wall thickness with position in the tree, age, conditions of growth, and kind of tree. The walls of the cells are formed principally of chain molecules of cellulose, polymerized from glucose residues and oriented as a partly crystalline material. These chains are aggregated in the cell wall at a variable angle, roughly parallel to the axis of the cell. The cells are cemented by an amorphous material called lignin. The complex structure of the gross wood approximates a rhombic system. The direction parallel to the grain and the axis of the stem is longitudinal (L), the two axes across the grain are radial (R) and tangential (T) with respect to the cylinder of the tree stem. This anisotropy and the molecular orientation account for the major differences in physical and mechanical properties with respect to direction which are present in wood.

Citation

Green, David W.; White, Robert H.; TenWolde, Antoni; Simpson, William; Murphy, Joseph; Ross, Robert J.; Hernandez, Roland; Lebow, Stan T. 2006. Wood. Marks'' standard handbook for mechanical engineers. New York : McGraw-Hill, 2006: ISBN: 0071428674: 9780071428675: Pages 6.115-6.131