How to compare yield/tensile/compressive strengths of materials different thickness

denver75

I understand the distinctions of the different types of material strengths, but I get stumped when asked about how they apply when the material discussed is thicker or thinner. Any help?

minger

Theoretically the material strengths are a function of material only, not geometry. However, in real practice, there can be slight variations, particularly when talking about very thin pieces. This can occur due to localized material problems along with some non-linear deformations when the part is loaded.

denver75

Thanks minger-
So in the discussion of how "strong" different thicknesses of materials are compared to each other, what would be the proper measurement? How can I describe 14 gauge vs 16 gauge sheet metal, or 1/2" plywood vs 3/4"?

xxChrisxx

Load capacity is probably the best way. A 14 gauge can carry more than 16 gauge, you've got to be careful though as this isnt material strength, its a funny combination of material strength and geometry.

So to say a thick sheet of metal is stonger than a thin sheet in the materal sense is wrong. Plywood is also a dodgy example as its non homogeneous. So it can have different material strengths depending on how the layers are oriented.

FredGarvin

You would still want to talk about stresses. Stresses are the great equalizer when it comes to talking and comparing scenarios and materials.

Plywood is actually pretty tough because of a few reasons:
1) It is non-homogeneous, i.e. it's properties will vary due to the nature of wood and adhesives.
2) It is non-isotropic, i.e. it's material properties usually are not the same in all directions like most metals.
3) It's properties will depend greatly on moisture content.