Managed tree plantations (genetic engineering, thinning, protein and fertilization) has resulted in greater proportions of earlywood. Difference in moduli found to be as high as seven.
-- "Mesostructure Elastic Properties in Loblolly Pine" by S. Cramer
Material Density
(Mg/m3)Modulus
(GPa)Tensile Strength
(MPa)Wood 0.1-1 0.2-20 25-100 Polymer 1-2 0.01-10 5-100 Ceramic 1-5 10-1000 1-800 Metal 2-10 50-200 50-2000
Material Specific
Strength
(x105 psi)Specific
Modulus
(x107 psi)Clear wood 7 9.5 Aluminum 5 10.5 1020 steel 2 10.5 Copper 1.5 5.5 Concrete 0.6 3.5
E varies a lot between wood types and between individual samples within the same type, due to variations in grain pattern and knot size and quantity.
Wood Density
(for 12% water)
(g/cm3)Modulus
of Elasticity
(psi)Cedar 0.32 1,100,000 Pine 0.35 1,200,000 Fir 0.48 2,000,000 Maple 0.48 1,500,000 Birch 0.62 2,000,000 Oak 0.68 1,800,000
Strengths also vary greatly. Note the anisotropic behavior of the following wood types classified by grain pattern and load type.
Wood Tensile
Strength
Longitudinal
(psi)Tensile
Strength
Radial
(psi)Compressive
Strength
Longitudinal
(psi)Compressive
Strength
Radial
(psi)
from The Science and Technology of Civil Engineering
Materials, J.F. Young, et al., Prentice Hall, 1998.Beech 12,500 1,010 7,300 1,010 Elm 17,500 660 5,520 690 Maple 15,700 1,100 7,830 1,470 Oak 11,300 940 6,200 810 Cedar 6,600 320 6,020 920 Fir 11,300 390 5,460 610 Pine 10,600 310 4,800 440 Spruce 8,600 370 5,610 580
from Engineering Materials 2, M.F.
Ashby, R.H. Jones, Pergamon Press,
1986, p. 260.
In summary, the mechanical properties of wood relate directly to the shape and size of its cells, and to the properties of the composite-like cell walls. Loaded along the grain, the cell walls are loaded in simple tension or compression, and the properties scale as the density. But across the grain, the cell walls bend, and then the properties depend on a power (3/2 to 2) of the density. That, plus the considerable anisotropy of the cell wall material, explain the enormous difference between the modulus, strength and toughness along the grain and across it. from Engineering Materials 2: An Introduction to Microstructures, Processing and Design, M.F. Ashby & D.R.H. Jones, Pergamon, 1994, p. 263.