What is the tensile strength of wood

Tensile and tear strength

Tensile strength is the resistance of the wood to the separation of its fibers in the longitudinal direction by tearing or tearing off. It is important for struts or crossbars in wooden towers, half-timbered structures, for drawbars, etc. The coarser anatomical structure as well as the fine structure of the wood allow for high tensile strength in the direction of the grain expect. The tensile strength of the threads practically does not depend on the strength of the main valence chains, but on the resistance of the micelle to lateral sliding.

The tensile strength strongly depends on the extent to which the direction of pull and the direction of the fiber coincide. If they only form an angle of 15 °, the tensile strength is reduced by half. It is extremely strongly reduced by knottiness; so the tensile strength of knotty pine wood was only about one sixth of the tensile strength of knotty pine wood. Growing density the tensile strength increases, with increasing wood moisture it decreases, but not to the same extent as the compressive strength.

The tensile strength of solid wood is relatively seldom determined because its determination is associated with certain difficulties and because in practice it is of less importance than other strength properties. The latter is related to the fact that the tensile strength measured on small, faultless samples does not provide a reliable guide to the tensile strength of larger pieces of the same trunk, since branches and growth defects have a very strong influence. However, in cases where specially selected valuable wood is processed (for example in aircraft construction) and in the case of tempered wood, in which the growth properties are largely balanced, one cannot do without testing the tensile strength. Tension members often appear in structural engineering, especially in timber engineering structures; Their resistance to tensile forces can only be properly characterized if test pieces with the same cross-section the structural members are torn in sufficiently large test facilities.

When the wood is stressed in the construction industry, tensile stresses across the grain are carefully prevented, since in many cases the unavoidable radial shrinkage cracks would directly endanger the cohesion of the wood.