Calculating Modulus of elasticity for a porous plastic (UHMW-Polyethylene)

Im trying to calculate the modulus of elasticity of a porous plastic
(UHMW-Polyethylene). I have a porous cylinder which is used for
biomedical research. which was manufactured by Porex Plastics Ind.
However the company has no material properties. Im able to get the
density of the plastic, and the nominal density of the porous plastic,
I know the porosity and the pore size, I heard that there is a way to
calculate the modulus of elasticity using a equtions when you know
those parameters. Is this true? ANy help would be greatly appreciated
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You would certainly need to know more, such as the mechanical properties of the nonporous plastic and the pore size distribution, and maybe even the orientation and connectivity of the pores. Given all of this, I would think that you might be able to patch together something that could be somewhat predicitive. Maybe it has already been done, such as you suggest.
Regardless, it seems to me that it would be easiest to just measure the properties you are after. Then you would clearly know, as opposed to having a theoretical model with some unknown error built into it.
My employer can certainly help you measure it.
John Aspen Research, -
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On 25 Apr 2005 15:57:45 -0700, (ukesoccer) enriched cyberspace with these bytes:
As Mr. Spevacek already indicated in his reply, you need to know more than just the porosity and pore size to calculate the mechanical properties. In general terms mechanical properties of a porous material can be expressed with the following equation (doesn't hold true for microcellular material though):
Pp/Ps = C * (Dp/Ds)^n
where P is the property you're looking at and D is the density. The p and s stand for porous and solid. The power n depends on the property (E-modulus, compression strength, etc) that is considered and cell geometry. C is a correction factor (for instance dependent on anisotropy).
When all parameters are known, the equation can predict actual properties with a fair probability. Extensive info and derivation of more accurate equations can be found in "Cellular solids: structure and properties" by Gibson and Ashby (Cambridge University Press).
I have to agree with Mr. Spevacek, you'll get an accurate answer much quicker by just doing a test on the material.
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