Derive Porosity from Stiffness Value

I have the Young's modulus (stiffness) values of a hydro-gel scaffolds, and I need to know the porosity of those scaffolds.

I read about Nielsen Equation, which is this: $$E = \frac{E_0 (1 - P) ^ 2}{1 + \frac{P}{f - 1}}$$ where $$E$$ is Young’s modulus, $$E_0$$ is Young’s modulus for pore-less sample, $$P$$ is volume fraction of porosities, and $$f$$ is shape factor.

I have the following questions:

1. How to get the values of $$f$$ and $$E_0$$?
2. Any other methods to calculate porosity given material stiffness?
• Although I don't have it on hand to check, you may find Gibson and Ashby's Cellular Solids helpful, as it links scaffold geometries to mechanical properties. – Chemomechanics Jan 11 at 22:40