The modulus of elasticity of wood is the highest in the longitudinal direction, and it range usually lies between 1 million and 2 million psi (6.9 and 13.8GPa). The modulus of elasticity in radial direction is around 10% of that in longitudinal direction, and that in tangential direction is about one-half of that in radial direction.
The compressive
strength of wood parallel to the grain is much greater than that perpendicular
to grain. The compressive strength perpendicular to the grain is about 12% to
18% of that parallel to grain.
The maximum
bending stress is also expressed as modulus of rupture. Failure of timber member
subject to bending usually starts with wrinkling and crushing of compression
zone fibres, followed by splitting or snapping of tension zone fibres.
The tensile
strength of wood parallel to grain is the greatest of all strength
characteristics. It is about two to four times the compressive strength parallel
to the grain. The tensile strength of wood perpendicular to the grain is very
small, and it is usually taken as zero during allowable stress design.
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