Honeycomb Torsion Box Article - Techinical

[brian c miller]

Link here:

http://users.auth.gr/~jbarb/Publications/lightweight%20honeycomb%20furniture.pdf

Basic concept it to compare 8mm , 2x 8mm, 16mm particle board against 2 8mm sheet seprate by 35mm paper core.

[Chris Friesen]

I question their conclusions that the paper honeycomb panel is unsuitable.

They show the Modulus of Elasticity for the panel as a whole, without showing the stiffness of the resulting structure.

Given that stiffness of a rectangular beam increases with the third power of the thickness, but only linearly with the modulus of elasticity, the honeycomb panel (which is 3x thicker than the two skins separately) will be roughly 5x stiffer than the 16mm solid panel even though its MOE is substantially lower.

[Steve Kohn]

I question their conclusions that the paper honeycomb panel is unsuitable.

They show the Modulus of Elasticity for the panel as a whole, without showing the stiffness of the resulting structure.

Given that stiffness of a rectangular beam increases with the third power of the thickness, but only linearly with the modulus of elasticity, the honeycomb panel (which is 3x thicker than the two skins separately) will be roughly 5x stiffer than the 16mm solid panel even though its MOE is substantially lower.

+1, Whatever he said.

[brian c miller]

I too am a little throw off my their conclusions. The reference "the mechanical requirements of furniture making" through the article but do not state implicitly what the requirement are.

The interesting part to me was the impact bending strength to density ratio was 5X that of laminate particle board... to me that would suggest that if thick was not a concern the honeycomb panel was the clear winner for a rigid light weight panel. This shouldn’t be ground breaking however.

For me the conclusions of “not sufficient” is somewhat irrelevant give the conditions for sufficient are spelled out.

[D Randall]

+1, Whatever he said.

I'll go along with what ever he said too. He sounds too smart to be wrong.;)

[Chris Friesen]

I'll go along with what ever he said too. He sounds too smart to be wrong.;)

Hah...that's what a class in first-year statics gets you, I guess. :)

If anyone is interested:

The modulus of elasticity (MOE) is basically a number that describes how resistant a given material is to bending. Generally it's applied to uniform materials, but in this case they're calculating it for the honeycomb panel as a whole.

The area moment of inertia is basically a number that describes how stiff a given cross-sectional shape is. For a rectangular beam, it's proportional to the width times the cube of the height.

Using the moment of inertia and the modulus of elasticity and other factors you can figure out the beam deflection under a given load.

Going back to the article, the MOE for the honeycomb panel is lower than for the solid panels (because the honeycomb doesn't contribute much strength), but the overall stiffness of the honeycomb panel will be substantially higher because it is so much thicker. This is pretty much the whole point of a torsion box.

[Jim German]

Honeycomb panels can be incredibly strong, and incredibly light. They do have a significant number of other issues though, particularly with moisture getting into them. They're used all the time in aerospace applications.

The question of their suitability for furniture, for me at least would be unrelated to how strong they are though. I'm sure if properly designed and manufactured you could make furniture out of honeycomb panels that would be stronger and lighter than a conventional piece. Of course lightness is not really a requirement for furniture, in fact I suspect the opposite is true. That more people would buy a heavier piece of furniture than a lighter one, since it 'feels' of higher qualitly.

The other quesiton would be the cost of a honeycomb panel, and the increased design and constrcution costs. It seems unlikely that even considering the less raw material required to make a honeycomb panel, that it would end up being cheaper than plain MDF.

Lastly, using a honeycomb panel is significantly more difficult than a solid board, you can't really use screws or nails in it for instance.

[Noah Katz]

Given that stiffness of a rectangular beam increases with the third power of the thickness, but only linearly with the modulus of elasticity, the honeycomb panel (which is 3x thicker than the two skins separately) will be roughly 5x stiffer than the 16mm solid panel even though its MOE is substantially lower.

Bending stiffness increases w/the cube if it's a solid section, when you're increasing the spacing between two face sheets it increases w/the square.