(1)	$\begin{array}{l}\displaystyle E = E_0 \cdot \left( 1- \frac{\phi}{\phi_c} \right)^f\end{array}$

where

$\begin{array}{l}E_0\end{array}$	Young modulus of solid material
$\begin{array}{l}\phi\end{array}$	porosity	usually $\begin{array}{l}\phi \in 0 \div 0.4\end{array}$
$\begin{array}{l}\phi_c\end{array}$	critical porosity	usually $\begin{array}{l}\phi_c \approx 1\end{array}$
$\begin{array}{l}f\end{array}$	characteristic exponent	usually $\begin{array}{l}f \in 1.1 \div 1.7\end{array}$

Reference

1. K. K. PHANI andS. K. NIYOGI, J. Mater. Sci. 22 (1987) 257.

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