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Quote from: Tuomo on February 04, 2021, 02:41:42 amAlan - there is a small difference. See for example "Conners, T. & Medvecz, P. (1992). Wood As a Bimodular Material. Wood and Fiber Science 24, 413-423".In wood tensile modulus is about 8 % greater than compression modulus. But, of course there is a lot of variation. For example, in sugar maple the difference can be almost 28 %.Thanks for that paper, it is always nice to have some references to actual research. That much difference in sugar maple indicates that I should be heavily trapping every maple bow I make.Mark
Alan - there is a small difference. See for example "Conners, T. & Medvecz, P. (1992). Wood As a Bimodular Material. Wood and Fiber Science 24, 413-423".In wood tensile modulus is about 8 % greater than compression modulus. But, of course there is a lot of variation. For example, in sugar maple the difference can be almost 28 %.
Does anyone following Arvins testing method have access to a yew longbow with a sapwood back? I am curious how much of the elasticity in yew is attributable to the sapwood. A close to "circle of arc' tiller could be useful to easily make a calculation comparing the back stretch measurement to the whole.
I was going to quote similar. True tensile tests are not that common. I have seen numbers showing about 7500 for compressive in Maple and about 15000 for tensile. Very likely Hickory is similar.
Mark, did you have a chance to review the test data from the Canadian Forest Lab, where sugar maple excelled in certain tests? I am thinking those tests might serve as a proxy for tensile testing.
Conners and Medcevz are referencing Schnieder et al https://www.cabdirect.org/cabdirect/abstract/19920656871for the sugar maple data.
Quote from: PatM on February 04, 2021, 02:56:31 pmI was going to quote similar. True tensile tests are not that common. I have seen numbers showing about 7500 for compressive in Maple and about 15000 for tensile. Very likely Hickory is similar.Those sound like yield/rupture numbers and not modulus. I would expect sugar maple to be closer to 20,000psi for MOR but wood varies so much that you never know unless you measure the piece you are actually using.
Yes, I was just showing that they are different I think they do say that tensile strength and modulus of rupture are very similar in numbers.
That link requires a login to access.Mark
The treated sugar maple wood showed increases in MOE and MOR in bending by 20.0 and 28.0 %, respectively, as it was treated with a vinyl-type monomer to 51 % WPG. ...
I’m also curious if it has horn on belly and no set. Maybe the belly isn’t compressing as much as the back is stretching? Maybe elastic back is better for no set. Maybe why sinew and horn such a good combination? The capability of the back to stretch would help to keep the belly from having to crush.Bjrogg