In which direction is plywood strongest with respect to tensile strength?
Is it along the surface grain direction or perpendicular to it?
Is there a significant difference depending on the direction or is it roughly the same?
Is it along the surface grain direction or perpendicular to it?
Is there a significant difference depending on the direction or is it roughly the same?
Diagonally should be the strongest, right?
Immediately after I pressed "send," I realized that it's not at all obvious that it should be.
The maximum load diagonally to the fiber direction is probably less than "along," but is it greater, half, less than the sum of against-and-with the fiber direction under "straight" load?
More interesting question than I initially thought
Immediately after I pressed "send," I realized that it's not at all obvious that it should be.
The maximum load diagonally to the fiber direction is probably less than "along," but is it greater, half, less than the sum of against-and-with the fiber direction under "straight" load?
More interesting question than I initially thought
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I can't find anything about different directions in the documents I skimmed through anyway.
https://www.moelven.com/se/se/plywood-och-skivor/plywood/vanerply-prevent-k2070-oputsad-tg2/
https://www.moelven.com/se/se/plywood-och-skivor/plywood/vanerply-prevent-k2070-oputsad-tg2/
Plywood is strongest parallel to the "grain direction." The veneers are arranged in alternating directions, so the strongest direction is the one with the most veneers parallel to the "grain direction."
Plywood usually has an odd number of layers. This is so that both surface layers have the grain direction the same way. However, not all layers are always the same thickness. I believe the strength of the cross-grain veneers is negligible. So a guess is that the difference is proportional to the difference in the total thickness of the cross-grain and longitudinal veneers.
What prompts the question? It seems like a somewhat unusual application to have pure tensile load on plywood.
What prompts the question? It seems like a somewhat unusual application to have pure tensile load on plywood.
Fun with some laminate theory!
@Avemo and @bossespecial are absolutely correct, a veneer layer is much stronger in the fiber direction than across it, and with an odd number of layers, the surface layer's fiber direction is the strongest for the sheet. The difference naturally becomes smaller the more layers the sheet has. If there is bending load, the difference for different load directions becomes greater because the outermost layers take more load.
I found an interesting article here:
https://www.scionresearch.com/__data/assets/pdf_file/0005/59666/NZJFS1431984BIER349_367.pdf
On page 18, there is a nice compilation of test results with different setups and load types in several directions relative to the fiber direction of the outer layer.
@Avemo and @bossespecial are absolutely correct, a veneer layer is much stronger in the fiber direction than across it, and with an odd number of layers, the surface layer's fiber direction is the strongest for the sheet. The difference naturally becomes smaller the more layers the sheet has. If there is bending load, the difference for different load directions becomes greater because the outermost layers take more load.
I found an interesting article here:
https://www.scionresearch.com/__data/assets/pdf_file/0005/59666/NZJFS1431984BIER349_367.pdf
On page 18, there is a nice compilation of test results with different setups and load types in several directions relative to the fiber direction of the outer layer.
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