In the simplest terms, the modulus of elasticity (MOE) measures a wood’s stiffness, and is a good overall indicator of its strength.

Modulus of elasticity (MOE) testing

Modulus of elasticity (MOE) testing

Technically it’s a measurement of the ratio of stress placed upon the wood compared to the strain (deformation) that the wood exhibits along its length. MOE is expressed in pounds-force per square inch (lbf/in2) or gigapaschals (GPa). This number is given for wood that has been dried to a 12% moisture content, unless otherwise noted.

moe

In practical terms, the number itself isn’t all that meaningful, but it becomes useful to use in comparison with other woods. For instance, Hickory is known to have excellent strength properties among domestic species in the US, and has a MOE of 2,160,000 lbf/in2 (14.90 GPa). In comparison, Red Oak is another well-known wood used in cabinetry and furniture, and has a MOE of 1,820,000 lbf/in2 (12.50 GPa).

  • saar

    Hey, I have a question about MOR and MOE. How can it be that the MOE > MOR in some woods? How can there be less force required to break something rather than bend it?

    • ejmeier

      As I understand it, comparing MOE and MOR is like comparing apples and oranges: they’re really completely different types of measurements. (A fair comparison might be to compare MOR with Crushing Strength.)

      MOR and crushing strength are simple measurements of the wood until failure occurs. Basically, how much force did it require to break the wood of a given size (usually standardized sizes are used).

      MOE is a completely different animal in that it is a RATIO of two different measurements. It’s not only the force (stress) put on the wood, but also the amount that the wood has bent (strain). So it is stress DIVIDED by strain. So even if the stress does not exceed the theoretical MOR, if the strain is very low, you can come up with some very large MOE numbers due to a very small divisor.

      For instance, 1000 / 2 = 500
      but 1000 / .2 = 5000
      or even 1000 / .02 = 50000

  • saar

    I understand it much better now, thanks for taking the time to explain it :)

  • Steven

    Modulus elasticity is the ratio of stress to strain of a material in deflection (say in a beam) and is sometimes called ‘Young’s modulus’.

    The higher the values of Young’s modulus the better.

    Units: The units are ‘Pascals’ after the late French physicist – Blaise Pascal.
    And GigaPascals (GPa) are often used. For example: The Modulus elacticity of Steel is 200GPa, and some softwood timbers are around 7GPa.

    Steven McColl
    Structural Engineer.

    • ufg

      “better”
      I presume this means better for structural engineering?
      Higher value means more stiffness – which is not necessarily better for instrument making, probably archery and whatnot if the wood needs to bend a lot.

  • Returnto Sender

    I think you’d find that wood does bend easily given the same dimensions of steel. Try finding some rebar and a wooden dowel of the same diameter and length and compare the two.

  • Bernard KilBride

    Hello

    I am attempting to calculate whether a particular timber section (say C16 grade) will be strong enough, i.e. will not snap, under the wind load, and also the deflection at its tip. Can anyone help me with the formulae? i can work out the wind force and the bending moment at the posts base, just not how to determine its strength etc. i can do the maths once I know the formulae